code/trunk/pcre.c

/*************************************************
*      Perl-Compatible Regular Expressions       *
*************************************************/

/*
This is a library of functions to support regular expressions whose syntax
and semantics are as close as possible to those of the Perl 5 language. See
the file Tech.Notes for some information on the internals.

Written by: Philip Hazel <ph10@cam.ac.uk>

           Copyright (c) 1997-2003 University of Cambridge

-----------------------------------------------------------------------------
Permission is granted to anyone to use this software for any purpose on any
computer system, and to redistribute it freely, subject to the following
restrictions:

1. This software is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

2. The origin of this software must not be misrepresented, either by
   explicit claim or by omission.

3. Altered versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

4. If PCRE is embedded in any software that is released under the GNU
   General Purpose Licence (GPL), then the terms of that licence shall
   supersede any condition above with which it is incompatible.
-----------------------------------------------------------------------------
*/

/* Define DEBUG to get debugging output on stdout. */

/* #define DEBUG */

/* Use a macro for debugging printing, 'cause that eliminates the use of #ifdef
inline, and there are *still* stupid compilers about that don't like indented
pre-processor statements. I suppose it's only been 10 years... */

#ifdef DEBUG
#define DPRINTF(p) printf p
#else
#define DPRINTF(p) /*nothing*/
#endif

/* Include the internals header, which itself includes Standard C headers plus
the external pcre header. */

#include "internal.h"


/* Allow compilation as C++ source code, should anybody want to do that. */

#ifdef __cplusplus
#define class pcre_class
#endif


/* Maximum number of items on the nested bracket stacks at compile time. This
applies to the nesting of all kinds of parentheses. It does not limit
un-nested, non-capturing parentheses. This number can be made bigger if
necessary - it is used to dimension one int and one unsigned char vector at
compile time. */

#define BRASTACK_SIZE 200


/* Maximum number of ints of offset to save on the stack for recursive calls.
If the offset vector is bigger, malloc is used. This should be a multiple of 3,
because the offset vector is always a multiple of 3 long. */

#define REC_STACK_SAVE_MAX 30


/* The number of bytes in a literal character string above which we can't add
any more is set at 250 in order to allow for UTF-8 characters. (In theory it
could be 255 when UTF-8 support is excluded, but that means that some of the
test output would be different, which just complicates things.) */

#define MAXLIT 250


/* The maximum remaining length of subject we are prepared to search for a
req_byte match. */

#define REQ_BYTE_MAX 1000


/* Table of sizes for the fixed-length opcodes. It's defined in a macro so that
the definition is next to the definition of the opcodes in internal.h. */

static uschar OP_lengths[] = { OP_LENGTHS };

/* Min and max values for the common repeats; for the maxima, 0 => infinity */

static const char rep_min[] = { 0, 0, 1, 1, 0, 0 };
static const char rep_max[] = { 0, 0, 0, 0, 1, 1 };

/* Table for handling escaped characters in the range '0'-'z'. Positive returns
are simple data values; negative values are for special things like \d and so
on. Zero means further processing is needed (for things like \x), or the escape
is invalid. */

static const short int escapes[] = {
    0,      0,      0,      0,      0,      0,      0,      0,   /* 0 - 7 */
    0,      0,    ':',    ';',    '<',    '=',    '>',    '?',   /* 8 - ? */
  '@', -ESC_A, -ESC_B, -ESC_C, -ESC_D, -ESC_E,      0, -ESC_G,   /* @ - G */
    0,      0,      0,      0,      0,      0,      0,      0,   /* H - O */
    0, -ESC_Q,      0, -ESC_S,      0,      0,      0, -ESC_W,   /* P - W */
    0,      0, -ESC_Z,    '[',   '\\',    ']',    '^',    '_',   /* X - _ */
  '`',      7, -ESC_b,      0, -ESC_d,  ESC_e,  ESC_f,      0,   /* ` - g */
    0,      0,      0,      0,      0,      0,  ESC_n,      0,   /* h - o */
    0,      0,  ESC_r, -ESC_s,  ESC_tee,    0,      0, -ESC_w,   /* p - w */
    0,      0, -ESC_z                                            /* x - z */
};

/* Tables of names of POSIX character classes and their lengths. The list is
terminated by a zero length entry. The first three must be alpha, upper, lower,
as this is assumed for handling case independence. */

static const char *posix_names[] = {
  "alpha", "lower", "upper",
  "alnum", "ascii", "blank", "cntrl", "digit", "graph",
  "print", "punct", "space", "word",  "xdigit" };

static const uschar posix_name_lengths[] = {
  5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 4, 6, 0 };

/* Table of class bit maps for each POSIX class; up to three may be combined
to form the class. The table for [:blank:] is dynamically modified to remove
the vertical space characters. */

static const int posix_class_maps[] = {
  cbit_lower, cbit_upper, -1,             /* alpha */
  cbit_lower, -1,         -1,             /* lower */
  cbit_upper, -1,         -1,             /* upper */
  cbit_digit, cbit_lower, cbit_upper,     /* alnum */
  cbit_print, cbit_cntrl, -1,             /* ascii */
  cbit_space, -1,         -1,             /* blank - a GNU extension */
  cbit_cntrl, -1,         -1,             /* cntrl */
  cbit_digit, -1,         -1,             /* digit */
  cbit_graph, -1,         -1,             /* graph */
  cbit_print, -1,         -1,             /* print */
  cbit_punct, -1,         -1,             /* punct */
  cbit_space, -1,         -1,             /* space */
  cbit_word,  -1,         -1,             /* word - a Perl extension */
  cbit_xdigit,-1,         -1              /* xdigit */
};

/* Table to identify ASCII digits and hex digits. This is used when compiling
patterns. Note that the tables in chartables are dependent on the locale, and
may mark arbitrary characters as digits - but the PCRE compiling code expects
to handle only 0-9, a-z, and A-Z as digits when compiling. That is why we have
a private table here. It costs 256 bytes, but it is a lot faster than doing
character value tests (at least in some simple cases I timed), and in some
applications one wants PCRE to compile efficiently as well as match
efficiently.

For convenience, we use the same bit definitions as in chartables:

  0x04   decimal digit
  0x08   hexadecimal digit

Then we can use ctype_digit and ctype_xdigit in the code. */

static const unsigned char digitab[] =
  {
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*   0-  7 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*   8- 15 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  16- 23 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  24- 31 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*    - '  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  ( - /  */
  0x0c,0x0c,0x0c,0x0c,0x0c,0x0c,0x0c,0x0c, /*  0 - 7  */
  0x0c,0x0c,0x00,0x00,0x00,0x00,0x00,0x00, /*  8 - ?  */
  0x00,0x08,0x08,0x08,0x08,0x08,0x08,0x00, /*  @ - G  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  H - O  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  P - W  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  X - _  */
  0x00,0x08,0x08,0x08,0x08,0x08,0x08,0x00, /*  ` - g  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  h - o  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  p - w  */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /*  x -127 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 128-135 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 136-143 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 144-151 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 152-159 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 160-167 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 168-175 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 176-183 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 184-191 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 192-199 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 200-207 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 208-215 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 216-223 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 224-231 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 232-239 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* 240-247 */
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00};/* 248-255 */

/* Definition to allow mutual recursion */

static BOOL
  compile_regex(int, int, int *, uschar **, const uschar **, const char **,
    BOOL, int, int *, int *, branch_chain *, compile_data *);

/* Structure for building a chain of data that actually lives on the
stack, for holding the values of the subject pointer at the start of each
subpattern, so as to detect when an empty string has been matched by a
subpattern - to break infinite loops. */

typedef struct eptrblock {
  struct eptrblock *prev;
  const uschar *saved_eptr;
} eptrblock;

/* Flag bits for the match() function */

#define match_condassert   0x01    /* Called to check a condition assertion */
#define match_isgroup      0x02    /* Set if start of bracketed group */

/* Non-error returns from the match() function. Error returns are externally
defined PCRE_ERROR_xxx codes, which are all negative. */

#define MATCH_MATCH        1
#define MATCH_NOMATCH      0


/*************************************************
*               Global variables                 *
*************************************************/

/* PCRE is thread-clean and doesn't use any global variables in the normal
sense. However, it calls memory allocation and free functions via the two
indirections below, and it can optionally do callouts. These values can be
changed by the caller, but are shared between all threads. However, when
compiling for Virtual Pascal, things are done differently (see pcre.in). */

#ifndef VPCOMPAT
#ifdef __cplusplus
extern "C" void *(*pcre_malloc)(size_t) = malloc;
extern "C" void  (*pcre_free)(void *) = free;
extern "C" int   (*pcre_callout)(pcre_callout_block *) = NULL;
#else
void *(*pcre_malloc)(size_t) = malloc;
void  (*pcre_free)(void *) = free;
int   (*pcre_callout)(pcre_callout_block *) = NULL;
#endif
#endif


/*************************************************
*    Macros and tables for character handling    *
*************************************************/

/* When UTF-8 encoding is being used, a character is no longer just a single
byte. The macros for character handling generate simple sequences when used in
byte-mode, and more complicated ones for UTF-8 characters. */

#ifndef SUPPORT_UTF8
#define GETCHAR(c, eptr) c = *eptr;
#define GETCHARINC(c, eptr) c = *eptr++;
#define GETCHARINCTEST(c, eptr) c = *eptr++;
#define GETCHARLEN(c, eptr, len) c = *eptr;
#define BACKCHAR(eptr)

#else   /* SUPPORT_UTF8 */

/* Get the next UTF-8 character, not advancing the pointer. This is called when
we know we are in UTF-8 mode. */

#define GETCHAR(c, eptr) \
  c = *eptr; \
  if ((c & 0xc0) == 0xc0) \
    { \
    int gcii; \
    int gcaa = utf8_table4[c & 0x3f];  /* Number of additional bytes */ \
    int gcss = 6*gcaa; \
    c = (c & utf8_table3[gcaa]) << gcss; \
    for (gcii = 1; gcii <= gcaa; gcii++) \
      { \
      gcss -= 6; \
      c |= (eptr[gcii] & 0x3f) << gcss; \
      } \
    }

/* Get the next UTF-8 character, advancing the pointer. This is called when we
know we are in UTF-8 mode. */

#define GETCHARINC(c, eptr) \
  c = *eptr++; \
  if ((c & 0xc0) == 0xc0) \
    { \
    int gcaa = utf8_table4[c & 0x3f];  /* Number of additional bytes */ \
    int gcss = 6*gcaa; \
    c = (c & utf8_table3[gcaa]) << gcss; \
    while (gcaa-- > 0) \
      { \
      gcss -= 6; \
      c |= (*eptr++ & 0x3f) << gcss; \
      } \
    }

/* Get the next character, testing for UTF-8 mode, and advancing the pointer */

#define GETCHARINCTEST(c, eptr) \
  c = *eptr++; \
  if (md->utf8 && (c & 0xc0) == 0xc0) \
    { \
    int gcaa = utf8_table4[c & 0x3f];  /* Number of additional bytes */ \
    int gcss = 6*gcaa; \
    c = (c & utf8_table3[gcaa]) << gcss; \
    while (gcaa-- > 0) \
      { \
      gcss -= 6; \
      c |= (*eptr++ & 0x3f) << gcss; \
      } \
    }

/* Get the next UTF-8 character, not advancing the pointer, incrementing length
if there are extra bytes. This is called when we know we are in UTF-8 mode. */

#define GETCHARLEN(c, eptr, len) \
  c = *eptr; \
  if ((c & 0xc0) == 0xc0) \
    { \
    int gcii; \
    int gcaa = utf8_table4[c & 0x3f];  /* Number of additional bytes */ \
    int gcss = 6*gcaa; \
    c = (c & utf8_table3[gcaa]) << gcss; \
    for (gcii = 1; gcii <= gcaa; gcii++) \
      { \
      gcss -= 6; \
      c |= (eptr[gcii] & 0x3f) << gcss; \
      } \
    len += gcaa; \
    }

/* If the pointer is not at the start of a character, move it back until
it is. Called only in UTF-8 mode. */

#define BACKCHAR(eptr) while((*eptr & 0xc0) == 0x80) eptr--;

#endif


/*************************************************
*             Default character tables           *
*************************************************/

/* A default set of character tables is included in the PCRE binary. Its source
is built by the maketables auxiliary program, which uses the default C ctypes
functions, and put in the file chartables.c. These tables are used by PCRE
whenever the caller of pcre_compile() does not provide an alternate set of
tables. */

#include "chartables.c"


#ifdef SUPPORT_UTF8
/*************************************************
*           Tables for UTF-8 support             *
*************************************************/

/* These are the breakpoints for different numbers of bytes in a UTF-8
character. */

static const int utf8_table1[] =
  { 0x7f, 0x7ff, 0xffff, 0x1fffff, 0x3ffffff, 0x7fffffff};

/* These are the indicator bits and the mask for the data bits to set in the
first byte of a character, indexed by the number of additional bytes. */

static const int utf8_table2[] = { 0,    0xc0, 0xe0, 0xf0, 0xf8, 0xfc};
static const int utf8_table3[] = { 0xff, 0x1f, 0x0f, 0x07, 0x03, 0x01};

/* Table of the number of extra characters, indexed by the first character
masked with 0x3f. The highest number for a valid UTF-8 character is in fact
0x3d. */

static const uschar utf8_table4[] = {
  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
  3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5 };


/*************************************************
*       Convert character value to UTF-8         *
*************************************************/

/* This function takes an integer value in the range 0 - 0x7fffffff
and encodes it as a UTF-8 character in 0 to 6 bytes.

Arguments:
  cvalue     the character value
  buffer     pointer to buffer for result - at least 6 bytes long

Returns:     number of characters placed in the buffer
*/

static int
ord2utf8(int cvalue, uschar *buffer)
{
register int i, j;
for (i = 0; i < sizeof(utf8_table1)/sizeof(int); i++)
  if (cvalue <= utf8_table1[i]) break;
buffer += i;
for (j = i; j > 0; j--)
 {
 *buffer-- = 0x80 | (cvalue & 0x3f);
 cvalue >>= 6;
 }
*buffer = utf8_table2[i] | cvalue;
return i + 1;
}
#endif


/*************************************************
*         Print compiled regex                   *
*************************************************/

/* The code for doing this is held in a separate file that is also included in
pcretest.c. It defines a function called print_internals(). */

#ifdef DEBUG
#include "printint.c"
#endif


/*************************************************
*          Return version string                 *
*************************************************/

#define STRING(a)  # a
#define XSTRING(s) STRING(s)

const char *
pcre_version(void)
{
return XSTRING(PCRE_MAJOR) "." XSTRING(PCRE_MINOR) " " XSTRING(PCRE_DATE);
}


/*************************************************
* (Obsolete) Return info about compiled pattern  *
*************************************************/

/* This is the original "info" function. It picks potentially useful data out
of the private structure, but its interface was too rigid. It remains for
backwards compatibility. The public options are passed back in an int - though
the re->options field has been expanded to a long int, all the public options
at the low end of it, and so even on 16-bit systems this will still be OK.
Therefore, I haven't changed the API for pcre_info().

Arguments:
  external_re   points to compiled code
  optptr        where to pass back the options
  first_byte    where to pass back the first character,
                or -1 if multiline and all branches start ^,
                or -2 otherwise

Returns:        number of capturing subpatterns
                or negative values on error
*/

int
pcre_info(const pcre *external_re, int *optptr, int *first_byte)
{
const real_pcre *re = (const real_pcre *)external_re;
if (re == NULL) return PCRE_ERROR_NULL;
if (re->magic_number != MAGIC_NUMBER) return PCRE_ERROR_BADMAGIC;
if (optptr != NULL) *optptr = (int)(re->options & PUBLIC_OPTIONS);
if (first_byte != NULL)
  *first_byte = ((re->options & PCRE_FIRSTSET) != 0)? re->first_byte :
     ((re->options & PCRE_STARTLINE) != 0)? -1 : -2;
return re->top_bracket;
}


/*************************************************
*        Return info about compiled pattern      *
*************************************************/

/* This is a newer "info" function which has an extensible interface so
that additional items can be added compatibly.

Arguments:
  external_re      points to compiled code
  extra_data       points extra data, or NULL
  what             what information is required
  where            where to put the information

Returns:           0 if data returned, negative on error
*/

int
pcre_fullinfo(const pcre *external_re, const pcre_extra *extra_data, int what,
  void *where)
{
const real_pcre *re = (const real_pcre *)external_re;
const pcre_study_data *study = NULL;

if (re == NULL || where == NULL) return PCRE_ERROR_NULL;
if (re->magic_number != MAGIC_NUMBER) return PCRE_ERROR_BADMAGIC;

if (extra_data != NULL && (extra_data->flags & PCRE_EXTRA_STUDY_DATA) != 0)
  study = (const pcre_study_data *)extra_data->study_data;

switch (what)
  {
  case PCRE_INFO_OPTIONS:
  *((unsigned long int *)where) = re->options & PUBLIC_OPTIONS;
  break;

  case PCRE_INFO_SIZE:
  *((size_t *)where) = re->size;
  break;

  case PCRE_INFO_STUDYSIZE:
  *((size_t *)where) = (study == NULL)? 0 : study->size;
  break;

  case PCRE_INFO_CAPTURECOUNT:
  *((int *)where) = re->top_bracket;
  break;

  case PCRE_INFO_BACKREFMAX:
  *((int *)where) = re->top_backref;
  break;

  case PCRE_INFO_FIRSTBYTE:
  *((int *)where) =
    ((re->options & PCRE_FIRSTSET) != 0)? re->first_byte :
    ((re->options & PCRE_STARTLINE) != 0)? -1 : -2;
  break;

  case PCRE_INFO_FIRSTTABLE:
  *((const uschar **)where) =
    (study != NULL && (study->options & PCRE_STUDY_MAPPED) != 0)?
      study->start_bits : NULL;
  break;

  case PCRE_INFO_LASTLITERAL:
  *((int *)where) =
    ((re->options & PCRE_REQCHSET) != 0)? re->req_byte : -1;
  break;

  case PCRE_INFO_NAMEENTRYSIZE:
  *((int *)where) = re->name_entry_size;
  break;

  case PCRE_INFO_NAMECOUNT:
  *((int *)where) = re->name_count;
  break;

  case PCRE_INFO_NAMETABLE:
  *((const uschar **)where) = (const uschar *)re + sizeof(real_pcre);
  break;

  default: return PCRE_ERROR_BADOPTION;
  }

return 0;
}


/*************************************************
* Return info about what features are configured *
*************************************************/

/* This is function which has an extensible interface so that additional items
can be added compatibly.

Arguments:
  what             what information is required
  where            where to put the information

Returns:           0 if data returned, negative on error
*/

int
pcre_config(int what, void *where)
{
switch (what)
  {
  case PCRE_CONFIG_UTF8:
#ifdef SUPPORT_UTF8
  *((int *)where) = 1;
#else
  *((int *)where) = 0;
#endif
  break;

  case PCRE_CONFIG_NEWLINE:
  *((int *)where) = NEWLINE;
  break;

  case PCRE_CONFIG_LINK_SIZE:
  *((int *)where) = LINK_SIZE;
  break;

  case PCRE_CONFIG_POSIX_MALLOC_THRESHOLD:
  *((int *)where) = POSIX_MALLOC_THRESHOLD;
  break;

  case PCRE_CONFIG_MATCH_LIMIT:
  *((unsigned int *)where) = MATCH_LIMIT;
  break;

  default: return PCRE_ERROR_BADOPTION;
  }

return 0;
}


#ifdef DEBUG
/*************************************************
*        Debugging function to print chars       *
*************************************************/

/* Print a sequence of chars in printable format, stopping at the end of the
subject if the requested.

Arguments:
  p           points to characters
  length      number to print
  is_subject  TRUE if printing from within md->start_subject
  md          pointer to matching data block, if is_subject is TRUE

Returns:     nothing
*/

static void
pchars(const uschar *p, int length, BOOL is_subject, match_data *md)
{
int c;
if (is_subject && length > md->end_subject - p) length = md->end_subject - p;
while (length-- > 0)
  if (isprint(c = *(p++))) printf("%c", c); else printf("\\x%02x", c);
}
#endif


/*************************************************
*            Handle escapes                      *
*************************************************/

/* This function is called when a \ has been encountered. It either returns a
positive value for a simple escape such as \n, or a negative value which
encodes one of the more complicated things such as \d. When UTF-8 is enabled,
a positive value greater than 255 may be returned. On entry, ptr is pointing at
the \. On exit, it is on the final character of the escape sequence.

Arguments:
  ptrptr     points to the pattern position pointer
  errorptr   points to the pointer to the error message
  bracount   number of previous extracting brackets
  options    the options bits
  isclass    TRUE if inside a character class

Returns:     zero or positive => a data character
             negative => a special escape sequence
             on error, errorptr is set
*/

static int
check_escape(const uschar **ptrptr, const char **errorptr, int bracount,
  int options, BOOL isclass)
{
const uschar *ptr = *ptrptr;
int c, i;

/* If backslash is at the end of the pattern, it's an error. */

c = *(++ptr);
if (c == 0) *errorptr = ERR1;

/* Digits or letters may have special meaning; all others are literals. */

else if (c < '0' || c > 'z') {}

/* Do an initial lookup in a table. A non-zero result is something that can be
returned immediately. Otherwise further processing may be required. */

else if ((i = escapes[c - '0']) != 0) c = i;

/* Escapes that need further processing, or are illegal. */

else
  {
  const uschar *oldptr;
  switch (c)
    {
    /* A number of Perl escapes are not handled by PCRE. We give an explicit
    error. */

    case 'l':
    case 'L':
    case 'N':
    case 'p':
    case 'P':
    case 'u':
    case 'U':
    case 'X':
    *errorptr = ERR37;
    break;

    /* The handling of escape sequences consisting of a string of digits
    starting with one that is not zero is not straightforward. By experiment,
    the way Perl works seems to be as follows:

    Outside a character class, the digits are read as a decimal number. If the
    number is less than 10, or if there are that many previous extracting
    left brackets, then it is a back reference. Otherwise, up to three octal
    digits are read to form an escaped byte. Thus \123 is likely to be octal
    123 (cf \0123, which is octal 012 followed by the literal 3). If the octal
    value is greater than 377, the least significant 8 bits are taken. Inside a
    character class, \ followed by a digit is always an octal number. */

    case '1': case '2': case '3': case '4': case '5':
    case '6': case '7': case '8': case '9':

    if (!isclass)
      {
      oldptr = ptr;
      c -= '0';
      while ((digitab[ptr[1]] & ctype_digit) != 0)
        c = c * 10 + *(++ptr) - '0';
      if (c < 10 || c <= bracount)
        {
        c = -(ESC_REF + c);
        break;
        }
      ptr = oldptr;      /* Put the pointer back and fall through */
      }

    /* Handle an octal number following \. If the first digit is 8 or 9, Perl
    generates a binary zero byte and treats the digit as a following literal.
    Thus we have to pull back the pointer by one. */

    if ((c = *ptr) >= '8')
      {
      ptr--;
      c = 0;
      break;
      }

    /* \0 always starts an octal number, but we may drop through to here with a
    larger first octal digit. */

    case '0':
    c -= '0';
    while(i++ < 2 && ptr[1] >= '0' && ptr[1] <= '7')
        c = c * 8 + *(++ptr) - '0';
    c &= 255;     /* Take least significant 8 bits */
    break;

    /* \x is complicated when UTF-8 is enabled. \x{ddd} is a character number
    which can be greater than 0xff, but only if the ddd are hex digits. */

    case 'x':
#ifdef SUPPORT_UTF8
    if (ptr[1] == '{' && (options & PCRE_UTF8) != 0)
      {
      const uschar *pt = ptr + 2;
      register int count = 0;
      c = 0;
      while ((digitab[*pt] & ctype_xdigit) != 0)
        {
        int cc = *pt++;
        if (cc >= 'a') cc -= 32;            /* Convert to upper case */
        count++;
        c = c * 16 + cc - ((cc < 'A')? '0' : ('A' - 10));
        }
      if (*pt == '}')
        {
        if (c < 0 || count > 8) *errorptr = ERR34;
        ptr = pt;
        break;
        }
      /* If the sequence of hex digits does not end with '}', then we don't
      recognize this construct; fall through to the normal \x handling. */
      }
#endif

    /* Read just a single hex char */

    c = 0;
    while (i++ < 2 && (digitab[ptr[1]] & ctype_xdigit) != 0)
      {
      int cc;                               /* Some compilers don't like ++ */
      cc = *(++ptr);                        /* in initializers */
      if (cc >= 'a') cc -= 32;              /* Convert to upper case */
      c = c * 16 + cc - ((cc < 'A')? '0' : ('A' - 10));
      }
    break;

    /* Other special escapes not starting with a digit are straightforward */

    case 'c':
    c = *(++ptr);
    if (c == 0)
      {
      *errorptr = ERR2;
      return 0;
      }

    /* A letter is upper-cased; then the 0x40 bit is flipped. This coding
    is ASCII-specific, but then the whole concept of \cx is ASCII-specific. */

    if (c >= 'a' && c <= 'z') c -= 32;
    c ^= 0x40;
    break;

    /* PCRE_EXTRA enables extensions to Perl in the matter of escapes. Any
    other alphameric following \ is an error if PCRE_EXTRA was set; otherwise,
    for Perl compatibility, it is a literal. This code looks a bit odd, but
    there used to be some cases other than the default, and there may be again
    in future, so I haven't "optimized" it. */

    default:
    if ((options & PCRE_EXTRA) != 0) switch(c)
      {
      default:
      *errorptr = ERR3;
      break;
      }
    break;
    }
  }

*ptrptr = ptr;
return c;
}


/*************************************************
*            Check for counted repeat            *
*************************************************/

/* This function is called when a '{' is encountered in a place where it might
start a quantifier. It looks ahead to see if it really is a quantifier or not.
It is only a quantifier if it is one of the forms {ddd} {ddd,} or {ddd,ddd}
where the ddds are digits.

Arguments:
  p         pointer to the first char after '{'

Returns:    TRUE or FALSE
*/

static BOOL
is_counted_repeat(const uschar *p)
{
if ((digitab[*p++] && ctype_digit) == 0) return FALSE;
while ((digitab[*p] & ctype_digit) != 0) p++;
if (*p == '}') return TRUE;

if (*p++ != ',') return FALSE;
if (*p == '}') return TRUE;

if ((digitab[*p++] && ctype_digit) == 0) return FALSE;
while ((digitab[*p] & ctype_digit) != 0) p++;

return (*p == '}');
}


/*************************************************
*         Read repeat counts                     *
*************************************************/

/* Read an item of the form {n,m} and return the values. This is called only
after is_counted_repeat() has confirmed that a repeat-count quantifier exists,
so the syntax is guaranteed to be correct, but we need to check the values.

Arguments:
  p          pointer to first char after '{'
  minp       pointer to int for min
  maxp       pointer to int for max
             returned as -1 if no max
  errorptr   points to pointer to error message

Returns:     pointer to '}' on success;
             current ptr on error, with errorptr set
*/

static const uschar *
read_repeat_counts(const uschar *p, int *minp, int *maxp, const char **errorptr)
{
int min = 0;
int max = -1;

while ((digitab[*p] & ctype_digit) != 0) min = min * 10 + *p++ - '0';

if (*p == '}') max = min; else
  {
  if (*(++p) != '}')
    {
    max = 0;
    while((digitab[*p] & ctype_digit) != 0) max = max * 10 + *p++ - '0';
    if (max < min)
      {
      *errorptr = ERR4;
      return p;
      }
    }
  }

/* Do paranoid checks, then fill in the required variables, and pass back the
pointer to the terminating '}'. */

if (min > 65535 || max > 65535)
  *errorptr = ERR5;
else
  {
  *minp = min;
  *maxp = max;
  }
return p;
}


/*************************************************
*      Find first significant op code            *
*************************************************/

/* This is called by several functions that scan a compiled expression looking
for a fixed first character, or an anchoring op code etc. It skips over things
that do not influence this. For some calls, a change of option is important.

Arguments:
  code       pointer to the start of the group
  options    pointer to external options
  optbit     the option bit whose changing is significant, or
               zero if none are

Returns:     pointer to the first significant opcode
*/

static const uschar*
first_significant_code(const uschar *code, int *options, int optbit)
{
for (;;)
  {
  switch ((int)*code)
    {
    case OP_OPT:
    if (optbit > 0 && ((int)code[1] & optbit) != (*options & optbit))
      *options = (int)code[1];
    code += 2;
    break;

    case OP_ASSERT_NOT:
    case OP_ASSERTBACK:
    case OP_ASSERTBACK_NOT:
    do code += GET(code, 1); while (*code == OP_ALT);
    /* Fall through */

    case OP_CALLOUT:
    case OP_CREF:
    case OP_BRANUMBER:
    case OP_WORD_BOUNDARY:
    case OP_NOT_WORD_BOUNDARY:
    code += OP_lengths[*code];
    break;

    default:
    return code;
    }
  }
/* Control never reaches here */
}


/*************************************************
*        Find the fixed length of a pattern      *
*************************************************/

/* Scan a pattern and compute the fixed length of subject that will match it,
if the length is fixed. This is needed for dealing with backward assertions.
In UTF8 mode, the result is in characters rather than bytes.

Arguments:
  code     points to the start of the pattern (the bracket)
  options  the compiling options

Returns:   the fixed length, or -1 if there is no fixed length,
             or -2 if \C was encountered
*/

static int
find_fixedlength(uschar *code, int options)
{
int length = -1;

register int branchlength = 0;
register uschar *cc = code + 1 + LINK_SIZE;

/* Scan along the opcodes for this branch. If we get to the end of the
branch, check the length against that of the other branches. */

for (;;)
  {
  int d;
  register int op = *cc;
  if (op >= OP_BRA) op = OP_BRA;

  switch (op)
    {
    case OP_BRA:
    case OP_ONCE:
    case OP_COND:
    d = find_fixedlength(cc, options);
    if (d < 0) return d;
    branchlength += d;
    do cc += GET(cc, 1); while (*cc == OP_ALT);
    cc += 1 + LINK_SIZE;
    break;

    /* Reached end of a branch; if it's a ket it is the end of a nested
    call. If it's ALT it is an alternation in a nested call. If it is
    END it's the end of the outer call. All can be handled by the same code. */

    case OP_ALT:
    case OP_KET:
    case OP_KETRMAX:
    case OP_KETRMIN:
    case OP_END:
    if (length < 0) length = branchlength;
      else if (length != branchlength) return -1;
    if (*cc != OP_ALT) return length;
    cc += 1 + LINK_SIZE;
    branchlength = 0;
    break;

    /* Skip over assertive subpatterns */

    case OP_ASSERT:
    case OP_ASSERT_NOT:
    case OP_ASSERTBACK:
    case OP_ASSERTBACK_NOT:
    do cc += GET(cc, 1); while (*cc == OP_ALT);
    /* Fall through */

    /* Skip over things that don't match chars */

    case OP_REVERSE:
    case OP_BRANUMBER:
    case OP_CREF:
    case OP_OPT:
    case OP_CALLOUT:
    case OP_SOD:
    case OP_SOM:
    case OP_EOD:
    case OP_EODN:
    case OP_CIRC:
    case OP_DOLL:
    case OP_NOT_WORD_BOUNDARY:
    case OP_WORD_BOUNDARY:
    cc += OP_lengths[*cc];
    break;

    /* Handle char strings. In UTF-8 mode we must count characters, not bytes.
    This requires a scan of the string, unfortunately. We assume valid UTF-8
    strings, so all we do is reduce the length by one for every byte whose bits
    are 10xxxxxx. */

    case OP_CHARS:
    branchlength += *(++cc);
#ifdef SUPPORT_UTF8
    if ((options & PCRE_UTF8) != 0)
      for (d = 1; d <= *cc; d++)
        if ((cc[d] & 0xc0) == 0x80) branchlength--;
#endif
    cc += *cc + 1;
    break;

    /* Handle exact repetitions. The count is already in characters, but we
    need to skip over a multibyte character in UTF8 mode.  */

    case OP_EXACT:
    branchlength += GET2(cc,1);
    cc += 4;
#ifdef SUPPORT_UTF8
    if ((options & PCRE_UTF8) != 0)
      {
      while((*cc & 0x80) == 0x80) cc++;
      }
#endif
    break;

    case OP_TYPEEXACT:
    branchlength += GET2(cc,1);
    cc += 4;
    break;

    /* Handle single-char matchers */

    case OP_NOT_DIGIT:
    case OP_DIGIT:
    case OP_NOT_WHITESPACE:
    case OP_WHITESPACE:
    case OP_NOT_WORDCHAR:
    case OP_WORDCHAR:
    case OP_ANY:
    branchlength++;
    cc++;
    break;

    /* The single-byte matcher isn't allowed */

    case OP_ANYBYTE:
    return -2;

    /* Check a class for variable quantification */

#ifdef SUPPORT_UTF8
    case OP_XCLASS:
    cc += GET(cc, 1) - 33;
    /* Fall through */
#endif

    case OP_CLASS:
    case OP_NCLASS:
    cc += 33;

    switch (*cc)
      {
      case OP_CRSTAR:
      case OP_CRMINSTAR:
      case OP_CRQUERY:
      case OP_CRMINQUERY:
      return -1;

      case OP_CRRANGE:
      case OP_CRMINRANGE:
      if (GET2(cc,1) != GET2(cc,3)) return -1;
      branchlength += GET2(cc,1);
      cc += 5;
      break;

      default:
      branchlength++;
      }
    break;

    /* Anything else is variable length */

    default:
    return -1;
    }
  }
/* Control never gets here */
}


/*************************************************
*    Scan compiled regex for numbered bracket    *
*************************************************/

/* This little function scans through a compiled pattern until it finds a
capturing bracket with the given number.

Arguments:
  code        points to start of expression
  utf8        TRUE in UTF-8 mode
  number      the required bracket number

Returns:      pointer to the opcode for the bracket, or NULL if not found
*/

static const uschar *
find_bracket(const uschar *code, BOOL utf8, int number)
{
#ifndef SUPPORT_UTF8
utf8 = utf8;               /* Stop pedantic compilers complaining */
#endif

for (;;)
  {
  register int c = *code;
  if (c == OP_END) return NULL;
  else if (c == OP_CHARS) code += code[1] + OP_lengths[c];
  else if (c > OP_BRA)
    {
    int n = c - OP_BRA;
    if (n > EXTRACT_BASIC_MAX) n = GET2(code, 2+LINK_SIZE);
    if (n == number) return (uschar *)code;
    code += OP_lengths[OP_BRA];
    }
  else
    {
    code += OP_lengths[c];

    /* In UTF-8 mode, opcodes that are followed by a character may be followed
    by a multi-byte character. The length in the table is a minimum, so we have
    to scan along to skip the extra characters. All opcodes are less than 128,
    so we can use relatively efficient code. */

#ifdef SUPPORT_UTF8
    if (utf8) switch(c)
      {
      case OP_EXACT:
      case OP_UPTO:
      case OP_MINUPTO:
      case OP_STAR:
      case OP_MINSTAR:
      case OP_PLUS:
      case OP_MINPLUS:
      case OP_QUERY:
      case OP_MINQUERY:
      while ((*code & 0xc0) == 0x80) code++;
      break;
      }
#endif
    }
  }
}


/*************************************************
*    Scan compiled branch for non-emptiness      *
*************************************************/

/* This function scans through a branch of a compiled pattern to see whether it
can match the empty string or not. It is called only from could_be_empty()
below. Note that first_significant_code() skips over assertions. If we hit an
unclosed bracket, we return "empty" - this means we've struck an inner bracket
whose current branch will already have been scanned.

Arguments:
  code        points to start of search
  endcode     points to where to stop
  utf8        TRUE if in UTF8 mode

Returns:      TRUE if what is matched could be empty
*/

static BOOL
could_be_empty_branch(const uschar *code, const uschar *endcode, BOOL utf8)
{
register int c;
for (code = first_significant_code(code + 1 + LINK_SIZE, NULL, 0);
     code < endcode;
     code = first_significant_code(code + OP_lengths[c], NULL, 0))
  {
  const uschar *ccode;

  c = *code;

  if (c >= OP_BRA)
    {
    BOOL empty_branch;
    if (GET(code, 1) == 0) return TRUE;    /* Hit unclosed bracket */

    /* Scan a closed bracket */

    empty_branch = FALSE;
    do
      {
      if (!empty_branch && could_be_empty_branch(code, endcode, utf8))
        empty_branch = TRUE;
      code += GET(code, 1);
      }
    while (*code == OP_ALT);
    if (!empty_branch) return FALSE;   /* All branches are non-empty */
    code += 1 + LINK_SIZE;
    c = *code;
    }

  else switch (c)
    {
    /* Check for quantifiers after a class */

#ifdef SUPPORT_UTF8
    case OP_XCLASS:
    ccode = code + GET(code, 1);
    goto CHECK_CLASS_REPEAT;
#endif

    case OP_CLASS:
    case OP_NCLASS:
    ccode = code + 33;

#ifdef SUPPORT_UTF8
    CHECK_CLASS_REPEAT:
#endif

    switch (*ccode)
      {
      case OP_CRSTAR:            /* These could be empty; continue */
      case OP_CRMINSTAR:
      case OP_CRQUERY:
      case OP_CRMINQUERY:
      break;

      default:                   /* Non-repeat => class must match */
      case OP_CRPLUS:            /* These repeats aren't empty */
      case OP_CRMINPLUS:
      return FALSE;

      case OP_CRRANGE:
      case OP_CRMINRANGE:
      if (GET2(ccode, 1) > 0) return FALSE;  /* Minimum > 0 */
      break;
      }
    break;

    /* Opcodes that must match a character */

    case OP_NOT_DIGIT:
    case OP_DIGIT:
    case OP_NOT_WHITESPACE:
    case OP_WHITESPACE:
    case OP_NOT_WORDCHAR:
    case OP_WORDCHAR:
    case OP_ANY:
    case OP_ANYBYTE:
    case OP_CHARS:
    case OP_NOT:
    case OP_PLUS:
    case OP_MINPLUS:
    case OP_EXACT:
    case OP_NOTPLUS:
    case OP_NOTMINPLUS:
    case OP_NOTEXACT:
    case OP_TYPEPLUS:
    case OP_TYPEMINPLUS:
    case OP_TYPEEXACT:
    return FALSE;

    /* End of branch */

    case OP_KET:
    case OP_KETRMAX:
    case OP_KETRMIN:
    case OP_ALT:
    return TRUE;

    /* In UTF-8 mode, STAR, MINSTAR, QUERY, MINQUERY, UPTO, and MINUPTO  may be
    followed by a multibyte character */

#ifdef SUPPORT_UTF8
    case OP_STAR:
    case OP_MINSTAR:
    case OP_QUERY:
    case OP_MINQUERY:
    case OP_UPTO:
    case OP_MINUPTO:
    if (utf8) while ((code[2] & 0xc0) == 0x80) code++;
    break;
#endif
    }
  }

return TRUE;
}


/*************************************************
*    Scan compiled regex for non-emptiness       *
*************************************************/

/* This function is called to check for left recursive calls. We want to check
the current branch of the current pattern to see if it could match the empty
string. If it could, we must look outwards for branches at other levels,
stopping when we pass beyond the bracket which is the subject of the recursion.

Arguments:
  code        points to start of the recursion
  endcode     points to where to stop (current RECURSE item)
  bcptr       points to the chain of current (unclosed) branch starts
  utf8        TRUE if in UTF-8 mode

Returns:      TRUE if what is matched could be empty
*/

static BOOL
could_be_empty(const uschar *code, const uschar *endcode, branch_chain *bcptr,
  BOOL utf8)
{
while (bcptr != NULL && bcptr->current >= code)
  {
  if (!could_be_empty_branch(bcptr->current, endcode, utf8)) return FALSE;
  bcptr = bcptr->outer;
  }
return TRUE;
}


/*************************************************
*           Check for POSIX class syntax         *
*************************************************/

/* This function is called when the sequence "[:" or "[." or "[=" is
encountered in a character class. It checks whether this is followed by an
optional ^ and then a sequence of letters, terminated by a matching ":]" or
".]" or "=]".

Argument:
  ptr      pointer to the initial [
  endptr   where to return the end pointer
  cd       pointer to compile data

Returns:   TRUE or FALSE
*/

static BOOL
check_posix_syntax(const uschar *ptr, const uschar **endptr, compile_data *cd)
{
int terminator;          /* Don't combine these lines; the Solaris cc */
terminator = *(++ptr);   /* compiler warns about "non-constant" initializer. */
if (*(++ptr) == '^') ptr++;
while ((cd->ctypes[*ptr] & ctype_letter) != 0) ptr++;
if (*ptr == terminator && ptr[1] == ']')
  {
  *endptr = ptr;
  return TRUE;
  }
return FALSE;
}


/*************************************************
*          Check POSIX class name                *
*************************************************/

/* This function is called to check the name given in a POSIX-style class entry
such as [:alnum:].

Arguments:
  ptr        points to the first letter
  len        the length of the name

Returns:     a value representing the name, or -1 if unknown
*/

static int
check_posix_name(const uschar *ptr, int len)
{
register int yield = 0;
while (posix_name_lengths[yield] != 0)
  {
  if (len == posix_name_lengths[yield] &&
    strncmp((const char *)ptr, posix_names[yield], len) == 0) return yield;
  yield++;
  }
return -1;
}


/*************************************************
*           Compile one branch                   *
*************************************************/

/* Scan the pattern, compiling it into the code vector. If the options are
changed during the branch, the pointer is used to change the external options
bits.

Arguments:
  optionsptr     pointer to the option bits
  brackets       points to number of extracting brackets used
  code           points to the pointer to the current code point
  ptrptr         points to the current pattern pointer
  errorptr       points to pointer to error message
  firstbyteptr   set to initial literal character, or < 0 (REQ_UNSET, REQ_NONE)
  reqbyteptr     set to the last literal character required, else < 0
  bcptr          points to current branch chain
  cd             contains pointers to tables etc.

Returns:         TRUE on success
                 FALSE, with *errorptr set on error
*/

static BOOL
compile_branch(int *optionsptr, int *brackets, uschar **codeptr,
  const uschar **ptrptr, const char **errorptr, int *firstbyteptr,
  int *reqbyteptr, branch_chain *bcptr, compile_data *cd)
{
int repeat_type, op_type;
int repeat_min = 0, repeat_max = 0;      /* To please picky compilers */
int bravalue = 0;
int length;
int greedy_default, greedy_non_default;
int firstbyte, reqbyte;
int zeroreqbyte, zerofirstbyte;
int req_caseopt, reqvary, tempreqvary;
int condcount = 0;
int options = *optionsptr;
register int c;
register uschar *code = *codeptr;
uschar *tempcode;
BOOL inescq = FALSE;
BOOL groupsetfirstbyte = FALSE;
const uschar *ptr = *ptrptr;
const uschar *tempptr;
uschar *previous = NULL;
uschar class[32];

#ifdef SUPPORT_UTF8
BOOL class_utf8;
BOOL utf8 = (options & PCRE_UTF8) != 0;
uschar *class_utf8data;
uschar utf8_char[6];
#else
BOOL utf8 = FALSE;
#endif

/* Set up the default and non-default settings for greediness */

greedy_default = ((options & PCRE_UNGREEDY) != 0);
greedy_non_default = greedy_default ^ 1;

/* Initialize no first char, no required char. REQ_UNSET means "no char
matching encountered yet". It gets changed to REQ_NONE if we hit something that
matches a non-fixed char first char; reqbyte just remains unset if we never
find one.

When we hit a repeat whose minimum is zero, we may have to adjust these values
to take the zero repeat into account. This is implemented by setting them to
zerofirstbyte and zeroreqbyte when such a repeat is encountered. The individual
item types that can be repeated set these backoff variables appropriately. */

firstbyte = reqbyte = zerofirstbyte = zeroreqbyte = REQ_UNSET;

/* The variable req_caseopt contains either the REQ_CASELESS value or zero,
according to the current setting of the caseless flag. REQ_CASELESS is a bit
value > 255. It is added into the firstbyte or reqbyte variables to record the
case status of the value. */

req_caseopt = ((options & PCRE_CASELESS) != 0)? REQ_CASELESS : 0;

/* Switch on next character until the end of the branch */

for (;; ptr++)
  {
  BOOL negate_class;
  BOOL possessive_quantifier;
  int class_charcount;
  int class_lastchar;
  int newoptions;
  int recno;
  int skipbytes;
  int subreqbyte;
  int subfirstbyte;

  c = *ptr;
  if (inescq && c != 0) goto NORMAL_CHAR;

  if ((options & PCRE_EXTENDED) != 0)
    {
    if ((cd->ctypes[c] & ctype_space) != 0) continue;
    if (c == '#')
      {
      /* The space before the ; is to avoid a warning on a silly compiler
      on the Macintosh. */
      while ((c = *(++ptr)) != 0 && c != NEWLINE) ;
      if (c != 0) continue;   /* Else fall through to handle end of string */
      }
    }

  switch(c)
    {
    /* The branch terminates at end of string, |, or ). */

    case 0:
    case '|':
    case ')':
    *firstbyteptr = firstbyte;
    *reqbyteptr = reqbyte;
    *codeptr = code;
    *ptrptr = ptr;
    return TRUE;

    /* Handle single-character metacharacters. In multiline mode, ^ disables
    the setting of any following char as a first character. */

    case '^':
    if ((options & PCRE_MULTILINE) != 0)
      {
      if (firstbyte == REQ_UNSET) firstbyte = REQ_NONE;
      }
    previous = NULL;
    *code++ = OP_CIRC;
    break;

    case '$':
    previous = NULL;
    *code++ = OP_DOLL;
    break;

    /* There can never be a first char if '.' is first, whatever happens about
    repeats. The value of reqbyte doesn't change either. */

    case '.':
    if (firstbyte == REQ_UNSET) firstbyte = REQ_NONE;
    zerofirstbyte = firstbyte;
    zeroreqbyte = reqbyte;
    previous = code;
    *code++ = OP_ANY;
    break;

    /* Character classes. If the included characters are all < 255 in value, we
    build a 32-byte bitmap of the permitted characters, except in the special
    case where there is only one such character. For negated classes, we build
    the map as usual, then invert it at the end. However, we use a different
    opcode so that data characters > 255 can be handled correctly.

    If the class contains characters outside the 0-255 range, a different
    opcode is compiled. It may optionally have a bit map for characters < 256,
    but those above are are explicitly listed afterwards. A flag byte tells
    whether the bitmap is present, and whether this is a negated class or not.
    */

    case '[':
    previous = code;

    /* PCRE supports POSIX class stuff inside a class. Perl gives an error if
    they are encountered at the top level, so we'll do that too. */

    if ((ptr[1] == ':' || ptr[1] == '.' || ptr[1] == '=') &&
        check_posix_syntax(ptr, &tempptr, cd))
      {
      *errorptr = (ptr[1] == ':')? ERR13 : ERR31;
      goto FAILED;
      }

    /* If the first character is '^', set the negation flag and skip it. */

    if ((c = *(++ptr)) == '^')
      {
      negate_class = TRUE;
      c = *(++ptr);
      }
    else
      {
      negate_class = FALSE;
      }

    /* Keep a count of chars with values < 256 so that we can optimize the case
    of just a single character (as long as it's < 256). For higher valued UTF-8
    characters, we don't yet do any optimization. */

    class_charcount = 0;
    class_lastchar = -1;

#ifdef SUPPORT_UTF8
    class_utf8 = FALSE;                       /* No chars >= 256 */
    class_utf8data = code + LINK_SIZE + 34;   /* For UTF-8 items */
#endif

    /* Initialize the 32-char bit map to all zeros. We have to build the
    map in a temporary bit of store, in case the class contains only 1
    character (< 256), because in that case the compiled code doesn't use the
    bit map. */

    memset(class, 0, 32 * sizeof(uschar));

    /* Process characters until ] is reached. By writing this as a "do" it
    means that an initial ] is taken as a data character. The first pass
    through the regex checked the overall syntax, so we don't need to be very
    strict here. At the start of the loop, c contains the first byte of the
    character. */

    do
      {
#ifdef SUPPORT_UTF8
      if (utf8 && c > 127)
        {                           /* Braces are required because the */
        GETCHARLEN(c, ptr, ptr);    /* macro generates multiple statements */
        }
#endif

      /* Inside \Q...\E everything is literal except \E */

      if (inescq)
        {
        if (c == '\\' && ptr[1] == 'E')
          {
          inescq = FALSE;
          ptr++;
          continue;
          }
        else goto LONE_SINGLE_CHARACTER;
        }

      /* Handle POSIX class names. Perl allows a negation extension of the
      form [:^name:]. A square bracket that doesn't match the syntax is
      treated as a literal. We also recognize the POSIX constructions
      [.ch.] and [=ch=] ("collating elements") and fault them, as Perl
      5.6 and 5.8 do. */

      if (c == '[' &&
          (ptr[1] == ':' || ptr[1] == '.' || ptr[1] == '=') &&
          check_posix_syntax(ptr, &tempptr, cd))
        {
        BOOL local_negate = FALSE;
        int posix_class, i;
        register const uschar *cbits = cd->cbits;

        if (ptr[1] != ':')
          {
          *errorptr = ERR31;
          goto FAILED;
          }

        ptr += 2;
        if (*ptr == '^')
          {
          local_negate = TRUE;
          ptr++;
          }

        posix_class = check_posix_name(ptr, tempptr - ptr);
        if (posix_class < 0)
          {
          *errorptr = ERR30;
          goto FAILED;
          }

        /* If matching is caseless, upper and lower are converted to
        alpha. This relies on the fact that the class table starts with
        alpha, lower, upper as the first 3 entries. */

        if ((options & PCRE_CASELESS) != 0 && posix_class <= 2)
          posix_class = 0;

        /* Or into the map we are building up to 3 of the static class
        tables, or their negations. The [:blank:] class sets up the same
        chars as the [:space:] class (all white space). We remove the vertical
        white space chars afterwards. */

        posix_class *= 3;
        for (i = 0; i < 3; i++)
          {
          BOOL isblank = strncmp((char *)ptr, "blank", 5) == 0;
          int taboffset = posix_class_maps[posix_class + i];
          if (taboffset < 0) break;
          if (local_negate)
            {
            for (c = 0; c < 32; c++) class[c] |= ~cbits[c+taboffset];
            if (isblank) class[1] |= 0x3c;
            }
          else
            {
            for (c = 0; c < 32; c++) class[c] |= cbits[c+taboffset];
            if (isblank) class[1] &= ~0x3c;
            }
          }

        ptr = tempptr + 1;
        class_charcount = 10;  /* Set > 1; assumes more than 1 per class */
        continue;    /* End of POSIX syntax handling */
        }

      /* Backslash may introduce a single character, or it may introduce one
      of the specials, which just set a flag. Escaped items are checked for
      validity in the pre-compiling pass. The sequence \b is a special case.
      Inside a class (and only there) it is treated as backspace. Elsewhere
      it marks a word boundary. Other escapes have preset maps ready to
      or into the one we are building. We assume they have more than one
      character in them, so set class_charcount bigger than one. */

      if (c == '\\')
        {
        c = check_escape(&ptr, errorptr, *brackets, options, TRUE);
        if (-c == ESC_b) c = '\b';  /* \b is backslash in a class */

        if (-c == ESC_Q)            /* Handle start of quoted string */
          {
          if (ptr[1] == '\\' && ptr[2] == 'E')
            {
            ptr += 2; /* avoid empty string */
            }
          else inescq = TRUE;
          continue;
          }

        else if (c < 0)
          {
          register const uschar *cbits = cd->cbits;
          class_charcount = 10;     /* Greater than 1 is what matters */
          switch (-c)
            {
            case ESC_d:
            for (c = 0; c < 32; c++) class[c] |= cbits[c+cbit_digit];
            continue;

            case ESC_D:
            for (c = 0; c < 32; c++) class[c] |= ~cbits[c+cbit_digit];
            continue;

            case ESC_w:
            for (c = 0; c < 32; c++) class[c] |= cbits[c+cbit_word];
            continue;

            case ESC_W:
            for (c = 0; c < 32; c++) class[c] |= ~cbits[c+cbit_word];
            continue;

            case ESC_s:
            for (c = 0; c < 32; c++) class[c] |= cbits[c+cbit_space];
            class[1] &= ~0x08;   /* Perl 5.004 onwards omits VT from \s */
            continue;

            case ESC_S:
            for (c = 0; c < 32; c++) class[c] |= ~cbits[c+cbit_space];
            class[1] |= 0x08;    /* Perl 5.004 onwards omits VT from \s */
            continue;

            /* Unrecognized escapes are faulted if PCRE is running in its
            strict mode. By default, for compatibility with Perl, they are
            treated as literals. */

            default:
            if ((options & PCRE_EXTRA) != 0)
              {
              *errorptr = ERR7;
              goto FAILED;
              }
            c = *ptr;    /* The final character */
            }
          }

        /* Fall through if we have a single character (c >= 0). This may be
        > 256 in UTF-8 mode. */

        }   /* End of backslash handling */

      /* A single character may be followed by '-' to form a range. However,
      Perl does not permit ']' to be the end of the range. A '-' character
      here is treated as a literal. */

      if (ptr[1] == '-' && ptr[2] != ']')
        {
        int d;
        ptr += 2;

#ifdef SUPPORT_UTF8
        if (utf8)
          {                           /* Braces are required because the */
          GETCHARLEN(d, ptr, ptr);    /* macro generates multiple statements */
          }
        else
#endif
        d = *ptr;

        /* The second part of a range can be a single-character escape, but
        not any of the other escapes. Perl 5.6 treats a hyphen as a literal
        in such circumstances. */

        if (d == '\\')
          {
          const uschar *oldptr = ptr;
          d = check_escape(&ptr, errorptr, *brackets, options, TRUE);

          /* \b is backslash; any other special means the '-' was literal */

          if (d < 0)
            {
            if (d == -ESC_b) d = '\b'; else
              {
              ptr = oldptr - 2;
              goto LONE_SINGLE_CHARACTER;  /* A few lines below */
              }
            }
          }

        /* Check that the two values are in the correct order */

        if (d < c)
          {
          *errorptr = ERR8;
          goto FAILED;
          }

        /* If d is greater than 255, we can't just use the bit map, so set up
        for the UTF-8 supporting class type. If we are not caseless, we can
        just set up a single range. If we are caseless, the characters < 256
        are handled with a bitmap, in order to get the case-insensitive
        handling. */

#ifdef SUPPORT_UTF8
        if (d > 255)
          {
          class_utf8 = TRUE;
          *class_utf8data++ = XCL_RANGE;
          if ((options & PCRE_CASELESS) == 0)
            {
            class_utf8data += ord2utf8(c, class_utf8data);
            class_utf8data += ord2utf8(d, class_utf8data);
            continue;  /* Go get the next char in the class */
            }
          class_utf8data += ord2utf8(256, class_utf8data);
          class_utf8data += ord2utf8(d, class_utf8data);
          d = 255;
          /* Fall through */
          }
#endif
        /* We use the bit map if the range is entirely < 255, or if part of it
        is < 255 and matching is caseless. */

        for (; c <= d; c++)
          {
          class[c/8] |= (1 << (c&7));
          if ((options & PCRE_CASELESS) != 0)
            {
            int uc = cd->fcc[c];           /* flip case */
            class[uc/8] |= (1 << (uc&7));
            }
          class_charcount++;                /* in case a one-char range */
          class_lastchar = c;
          }

        continue;   /* Go get the next char in the class */
        }

      /* Handle a lone single character - we can get here for a normal
      non-escape char, or after \ that introduces a single character. */

      LONE_SINGLE_CHARACTER:

      /* Handle a multibyte character */

#ifdef SUPPORT_UTF8
      if (utf8 && c > 255)
        {
        class_utf8 = TRUE;
        *class_utf8data++ = XCL_SINGLE;
        class_utf8data += ord2utf8(c, class_utf8data);
        }
      else
#endif
      /* Handle a single-byte character */
        {
        class [c/8] |= (1 << (c&7));
        if ((options & PCRE_CASELESS) != 0)
          {
          c = cd->fcc[c];   /* flip case */
          class[c/8] |= (1 << (c&7));
          }
        class_charcount++;
        class_lastchar = c;
        }
      }

    /* Loop until ']' reached; the check for end of string happens inside the
    loop. This "while" is the end of the "do" above. */

    while ((c = *(++ptr)) != ']' || inescq);

    /* If class_charcount is 1, we saw precisely one character with a value <
    256. In UTF-8 mode, we can optimize if there were no characters >= 256 and
    the one character is < 128. In non-UTF-8 mode we can always optimize.

    The optimization throws away the bit map. We turn the item into a
    1-character OP_CHARS if it's positive, or OP_NOT if it's negative. Note
    that OP_NOT does not support multibyte characters. In the positive case, it
    can cause firstbyte to be set. Otherwise, there can be no first char if
    this item is first, whatever repeat count may follow. In the case of
    reqbyte, save the previous value for reinstating. */

#ifdef SUPPORT_UTF8
    if (class_charcount == 1 &&
          (!utf8 ||
          (!class_utf8 && class_lastchar < 128)))
#else
    if (class_charcount == 1)
#endif
      {
      zeroreqbyte = reqbyte;
      if (negate_class)
        {
        if (firstbyte == REQ_UNSET) firstbyte = REQ_NONE;
        zerofirstbyte = firstbyte;
        *code++ = OP_NOT;
        }
      else
        {
        if (firstbyte == REQ_UNSET)
          {
          zerofirstbyte = REQ_NONE;
          firstbyte = class_lastchar | req_caseopt;
          }
        else
          {
          zerofirstbyte = firstbyte;
          reqbyte = class_lastchar | req_caseopt | cd->req_varyopt;
          }
        *code++ = OP_CHARS;
        *code++ = 1;
        }
      *code++ = class_lastchar;
      break;  /* End of class handling */
      }       /* End of 1-byte optimization */

    /* Otherwise, if this is the first thing in the branch, there can be no
    first char setting, whatever the repeat count. Any reqbyte setting must
    remain unchanged after any kind of repeat. */

    if (firstbyte == REQ_UNSET) firstbyte = REQ_NONE;
    zerofirstbyte = firstbyte;
    zeroreqbyte = reqbyte;

    /* If there are characters with values > 255, we have to compile an
    extended class, with its own opcode. If there are no characters < 256,
    we can omit the bitmap. */

#ifdef SUPPORT_UTF8
    if (class_utf8)
      {
      *class_utf8data++ = XCL_END;    /* Marks the end of extra data */
      *code++ = OP_XCLASS;
      code += LINK_SIZE;
      *code = negate_class? XCL_NOT : 0;

      /* If the map is required, install it, and move on to the end of
      the extra data */

      if (class_charcount > 0)
        {
        *code++ |= XCL_MAP;
        memcpy(code, class, 32);
        code = class_utf8data;
        }

      /* If the map is not required, slide down the extra data. */

      else
        {
        int len = class_utf8data - (code + 33);
        memmove(code + 1, code + 33, len);
        code += len + 1;
        }

      /* Now fill in the complete length of the item */

      PUT(previous, 1, code - previous);
      break;   /* End of class handling */
      }
#endif

    /* If there are no characters > 255, negate the 32-byte map if necessary,
    and copy it into the code vector. If this is the first thing in the branch,
    there can be no first char setting, whatever the repeat count. Any reqbyte
    setting must remain unchanged after any kind of repeat. */

    if (negate_class)
      {
      *code++ = OP_NCLASS;
      for (c = 0; c < 32; c++) code[c] = ~class[c];
      }
    else
      {
      *code++ = OP_CLASS;
      memcpy(code, class, 32);
      }
    code += 32;
    break;

    /* Various kinds of repeat */

    case '{':
    if (!is_counted_repeat(ptr+1)) goto NORMAL_CHAR;
    ptr = read_repeat_counts(ptr+1, &repeat_min, &repeat_max, errorptr);
    if (*errorptr != NULL) goto FAILED;
    goto REPEAT;

    case '*':
    repeat_min = 0;
    repeat_max = -1;
    goto REPEAT;

    case '+':
    repeat_min = 1;
    repeat_max = -1;
    goto REPEAT;

    case '?':
    repeat_min = 0;
    repeat_max = 1;

    REPEAT:
    if (previous == NULL)
      {
      *errorptr = ERR9;
      goto FAILED;
      }

    if (repeat_min == 0)
      {
      firstbyte = zerofirstbyte;    /* Adjust for zero repeat */
      reqbyte = zeroreqbyte;        /* Ditto */
      }

    /* Remember whether this is a variable length repeat */

    reqvary = (repeat_min == repeat_max)? 0 : REQ_VARY;

    op_type = 0;                    /* Default single-char op codes */
    possessive_quantifier = FALSE;  /* Default not possessive quantifier */

    /* Save start of previous item, in case we have to move it up to make space
    for an inserted OP_ONCE for the additional '+' extension. */

    tempcode = previous;

    /* If the next character is '+', we have a possessive quantifier. This
    implies greediness, whatever the setting of the PCRE_UNGREEDY option.
    If the next character is '?' this is a minimizing repeat, by default,
    but if PCRE_UNGREEDY is set, it works the other way round. We change the
    repeat type to the non-default. */

    if (ptr[1] == '+')
      {
      repeat_type = 0;                  /* Force greedy */
      possessive_quantifier = TRUE;
      ptr++;
      }
    else if (ptr[1] == '?')
      {
      repeat_type = greedy_non_default;
      ptr++;
      }
    else repeat_type = greedy_default;

    /* If previous was a recursion, we need to wrap it inside brackets so that
    it can be replicated if necessary. */

    if (*previous == OP_RECURSE)
      {
      memmove(previous + 1 + LINK_SIZE, previous, 1 + LINK_SIZE);
      code += 1 + LINK_SIZE;
      *previous = OP_BRA;
      PUT(previous, 1, code - previous);
      *code = OP_KET;
      PUT(code, 1, code - previous);
      code += 1 + LINK_SIZE;
      }

    /* If previous was a string of characters, chop off the last one and use it
    as the subject of the repeat. If there was only one character, we can
    abolish the previous item altogether. If a one-char item has a minumum of
    more than one, ensure that it is set in reqbyte - it might not be if a
    sequence such as x{3} is the first thing in a branch because the x will
    have gone into firstbyte instead.  */

    if (*previous == OP_CHARS)
      {
      /* Deal with UTF-8 characters that take up more than one byte. It's
      easier to write this out separately than try to macrify it. Use c to
      hold the length of the character in bytes, plus 0x80 to flag that it's a
      length rather than a small character. */

#ifdef SUPPORT_UTF8
      if (utf8 && (code[-1] & 0x80) != 0)
        {
        uschar *lastchar = code - 1;
        while((*lastchar & 0xc0) == 0x80) lastchar--;
        c = code - lastchar;            /* Length of UTF-8 character */
        memcpy(utf8_char, lastchar, c); /* Save the char */
        if (lastchar == previous + 2)   /* There was only one character */
          {
          code = previous;              /* Abolish the previous item */
          }
        else
          {
          previous[1] -= c;             /* Adjust length of previous */
          code = lastchar;              /* Lost char off the end */
          tempcode = code;              /* Adjust position to be moved for '+' */
          }
        c |= 0x80;                      /* Flag c as a length */
        }
      else
#endif

      /* Handle the case of a single byte - either with no UTF8 support, or
      with UTF-8 disabled, or for a UTF-8 character < 128. */

        {
        c = *(--code);
        if (code == previous + 2)   /* There was only one character */
          {
          code = previous;              /* Abolish the previous item */
          if (repeat_min > 1) reqbyte = c | req_caseopt | cd->req_varyopt;
          }
        else
          {
          previous[1]--;             /* adjust length */
          tempcode = code;           /* Adjust position to be moved for '+' */
          }
        }

      goto OUTPUT_SINGLE_REPEAT;   /* Code shared with single character types */
      }

    /* If previous was a single negated character ([^a] or similar), we use
    one of the special opcodes, replacing it. The code is shared with single-
    character repeats by setting opt_type to add a suitable offset into
    repeat_type. OP_NOT is currently used only for single-byte chars. */

    else if (*previous == OP_NOT)
      {
      op_type = OP_NOTSTAR - OP_STAR;  /* Use "not" opcodes */
      c = previous[1];
      code = previous;
      goto OUTPUT_SINGLE_REPEAT;
      }

    /* If previous was a character type match (\d or similar), abolish it and
    create a suitable repeat item. The code is shared with single-character
    repeats by setting op_type to add a suitable offset into repeat_type. */

    else if (*previous < OP_EODN)
      {
      op_type = OP_TYPESTAR - OP_STAR;  /* Use type opcodes */
      c = *previous;
      code = previous;

      OUTPUT_SINGLE_REPEAT:

      /* If the maximum is zero then the minimum must also be zero; Perl allows
      this case, so we do too - by simply omitting the item altogether. */

      if (repeat_max == 0) goto END_REPEAT;

      /* Combine the op_type with the repeat_type */

      repeat_type += op_type;

      /* A minimum of zero is handled either as the special case * or ?, or as
      an UPTO, with the maximum given. */

      if (repeat_min == 0)
        {
        if (repeat_max == -1) *code++ = OP_STAR + repeat_type;
          else if (repeat_max == 1) *code++ = OP_QUERY + repeat_type;
        else
          {
          *code++ = OP_UPTO + repeat_type;
          PUT2INC(code, 0, repeat_max);
          }
        }

      /* The case {1,} is handled as the special case + */

      else if (repeat_min == 1 && repeat_max == -1)
        *code++ = OP_PLUS + repeat_type;

      /* The case {n,n} is just an EXACT, while the general case {n,m} is
      handled as an EXACT followed by an UPTO. An EXACT of 1 is optimized. */

      else
        {
        if (repeat_min != 1)
          {
          *code++ = OP_EXACT + op_type;  /* NB EXACT doesn't have repeat_type */
          PUT2INC(code, 0, repeat_min);
          }

        /* If the mininum is 1 and the previous item was a character string,
        we either have to put back the item that got cancelled if the string
        length was 1, or add the character back onto the end of a longer
        string. For a character type nothing need be done; it will just get
        put back naturally. Note that the final character is always going to
        get added below, so we leave code ready for its insertion. */

        else if (*previous == OP_CHARS)
          {
          if (code == previous) code += 2; else

          /* In UTF-8 mode, a multibyte char has its length in c, with the 0x80
          bit set as a flag. The length will always be between 2 and 6. */

#ifdef SUPPORT_UTF8
          if (utf8 && c >= 128) previous[1] += c & 7; else
#endif
          previous[1]++;
          }

        /*  For a single negated character we also have to put back the
        item that got cancelled. At present this applies only to single byte
        characters in any mode. */

        else if (*previous == OP_NOT) code++;

        /* If the maximum is unlimited, insert an OP_STAR. Before doing so,
        we have to insert the character for the previous code. In UTF-8 mode,
        long characters have their length in c, with the 0x80 bit as a flag. */

        if (repeat_max < 0)
          {
#ifdef SUPPORT_UTF8
          if (utf8 && c >= 128)
            {
            memcpy(code, utf8_char, c & 7);
            code += c & 7;
            }
          else
#endif
          *code++ = c;
          *code++ = OP_STAR + repeat_type;
          }

        /* Else insert an UPTO if the max is greater than the min, again
        preceded by the character, for the previously inserted code. */

        else if (repeat_max != repeat_min)
          {
#ifdef SUPPORT_UTF8
          if (utf8 && c >= 128)
            {
            memcpy(code, utf8_char, c & 7);
            code += c & 7;
            }
          else
#endif
          *code++ = c;
          repeat_max -= repeat_min;
          *code++ = OP_UPTO + repeat_type;
          PUT2INC(code, 0, repeat_max);
          }
        }

      /* The character or character type itself comes last in all cases. */

#ifdef SUPPORT_UTF8
      if (utf8 && c >= 128)
        {
        memcpy(code, utf8_char, c & 7);
        code += c & 7;
        }
      else
#endif

      *code++ = c;
      }

    /* If previous was a character class or a back reference, we put the repeat
    stuff after it, but just skip the item if the repeat was {0,0}. */

    else if (*previous == OP_CLASS ||
             *previous == OP_NCLASS ||
#ifdef SUPPORT_UTF8
             *previous == OP_XCLASS ||
#endif
             *previous == OP_REF)
      {
      if (repeat_max == 0)
        {
        code = previous;
        goto END_REPEAT;
        }
      if (repeat_min == 0 && repeat_max == -1)
        *code++ = OP_CRSTAR + repeat_type;
      else if (repeat_min == 1 && repeat_max == -1)
        *code++ = OP_CRPLUS + repeat_type;
      else if (repeat_min == 0 && repeat_max == 1)
        *code++ = OP_CRQUERY + repeat_type;
      else
        {
        *code++ = OP_CRRANGE + repeat_type;
        PUT2INC(code, 0, repeat_min);
        if (repeat_max == -1) repeat_max = 0;  /* 2-byte encoding for max */
        PUT2INC(code, 0, repeat_max);
        }
      }

    /* If previous was a bracket group, we may have to replicate it in certain
    cases. */

    else if (*previous >= OP_BRA || *previous == OP_ONCE ||
             *previous == OP_COND)
      {
      register int i;
      int ketoffset = 0;
      int len = code - previous;
      uschar *bralink = NULL;

      /* If the maximum repeat count is unlimited, find the end of the bracket
      by scanning through from the start, and compute the offset back to it
      from the current code pointer. There may be an OP_OPT setting following
      the final KET, so we can't find the end just by going back from the code
      pointer. */

      if (repeat_max == -1)
        {
        register uschar *ket = previous;
        do ket += GET(ket, 1); while (*ket != OP_KET);
        ketoffset = code - ket;
        }

      /* The case of a zero minimum is special because of the need to stick
      OP_BRAZERO in front of it, and because the group appears once in the
      data, whereas in other cases it appears the minimum number of times. For
      this reason, it is simplest to treat this case separately, as otherwise
      the code gets far too messy. There are several special subcases when the
      minimum is zero. */

      if (repeat_min == 0)
        {
        /* If the maximum is also zero, we just omit the group from the output
        altogether. */

        if (repeat_max == 0)
          {
          code = previous;
          goto END_REPEAT;
          }

        /* If the maximum is 1 or unlimited, we just have to stick in the
        BRAZERO and do no more at this point. */

        if (repeat_max <= 1)
          {
          memmove(previous+1, previous, len);
          code++;
          *previous++ = OP_BRAZERO + repeat_type;
          }

        /* If the maximum is greater than 1 and limited, we have to replicate
        in a nested fashion, sticking OP_BRAZERO before each set of brackets.
        The first one has to be handled carefully because it's the original
        copy, which has to be moved up. The remainder can be handled by code
        that is common with the non-zero minimum case below. We just have to
        adjust the value or repeat_max, since one less copy is required. */

        else
          {
          int offset;
          memmove(previous + 2 + LINK_SIZE, previous, len);
          code += 2 + LINK_SIZE;
          *previous++ = OP_BRAZERO + repeat_type;
          *previous++ = OP_BRA;

          /* We chain together the bracket offset fields that have to be
          filled in later when the ends of the brackets are reached. */

          offset = (bralink == NULL)? 0 : previous - bralink;
          bralink = previous;
          PUTINC(previous, 0, offset);
          }

        repeat_max--;
        }

      /* If the minimum is greater than zero, replicate the group as many
      times as necessary, and adjust the maximum to the number of subsequent
      copies that we need. If we set a first char from the group, and didn't
      set a required char, copy the latter from the former. */

      else
        {
        if (repeat_min > 1)
          {
          if (groupsetfirstbyte && reqbyte < 0) reqbyte = firstbyte;
          for (i = 1; i < repeat_min; i++)
            {
            memcpy(code, previous, len);
            code += len;
            }
          }
        if (repeat_max > 0) repeat_max -= repeat_min;
        }

      /* This code is common to both the zero and non-zero minimum cases. If
      the maximum is limited, it replicates the group in a nested fashion,
      remembering the bracket starts on a stack. In the case of a zero minimum,
      the first one was set up above. In all cases the repeat_max now specifies
      the number of additional copies needed. */

      if (repeat_max >= 0)
        {
        for (i = repeat_max - 1; i >= 0; i--)
          {
          *code++ = OP_BRAZERO + repeat_type;

          /* All but the final copy start a new nesting, maintaining the
          chain of brackets outstanding. */

          if (i != 0)
            {
            int offset;
            *code++ = OP_BRA;
            offset = (bralink == NULL)? 0 : code - bralink;
            bralink = code;
            PUTINC(code, 0, offset);
            }

          memcpy(code, previous, len);
          code += len;
          }

        /* Now chain through the pending brackets, and fill in their length
        fields (which are holding the chain links pro tem). */

        while (bralink != NULL)
          {
          int oldlinkoffset;
          int offset = code - bralink + 1;
          uschar *bra = code - offset;
          oldlinkoffset = GET(bra, 1);
          bralink = (oldlinkoffset == 0)? NULL : bralink - oldlinkoffset;
          *code++ = OP_KET;
          PUTINC(code, 0, offset);
          PUT(bra, 1, offset);
          }
        }

      /* If the maximum is unlimited, set a repeater in the final copy. We
      can't just offset backwards from the current code point, because we
      don't know if there's been an options resetting after the ket. The
      correct offset was computed above. */

      else code[-ketoffset] = OP_KETRMAX + repeat_type;
      }

    /* Else there's some kind of shambles */

    else
      {
      *errorptr = ERR11;
      goto FAILED;
      }

    /* If the character following a repeat is '+', we wrap the entire repeated
    item inside OP_ONCE brackets. This is just syntactic sugar, taken from
    Sun's Java package. The repeated item starts at tempcode, not at previous,
    which might be the first part of a string whose (former) last char we
    repeated. However, we don't support '+' after a greediness '?'. */

    if (possessive_quantifier)
      {
      int len = code - tempcode;
      memmove(tempcode + 1+LINK_SIZE, tempcode, len);
      code += 1 + LINK_SIZE;
      len += 1 + LINK_SIZE;
      tempcode[0] = OP_ONCE;
      *code++ = OP_KET;
      PUTINC(code, 0, len);
      PUT(tempcode, 1, len);
      }

    /* In all case we no longer have a previous item. We also set the
    "follows varying string" flag for subsequently encountered reqbytes if
    it isn't already set and we have just passed a varying length item. */

    END_REPEAT:
    previous = NULL;
    cd->req_varyopt |= reqvary;
    break;


    /* Start of nested bracket sub-expression, or comment or lookahead or
    lookbehind or option setting or condition. First deal with special things
    that can come after a bracket; all are introduced by ?, and the appearance
    of any of them means that this is not a referencing group. They were
    checked for validity in the first pass over the string, so we don't have to
    check for syntax errors here.  */

    case '(':
    newoptions = options;
    skipbytes = 0;

    if (*(++ptr) == '?')
      {
      int set, unset;
      int *optset;

      switch (*(++ptr))
        {
        case '#':                 /* Comment; skip to ket */
        ptr++;
        while (*ptr != ')') ptr++;
        continue;

        case ':':                 /* Non-extracting bracket */
        bravalue = OP_BRA;
        ptr++;
        break;

        case '(':
        bravalue = OP_COND;       /* Conditional group */

        /* Condition to test for recursion */

        if (ptr[1] == 'R')
          {
          code[1+LINK_SIZE] = OP_CREF;
          PUT2(code, 2+LINK_SIZE, CREF_RECURSE);
          skipbytes = 3;
          ptr += 3;
          }

        /* Condition to test for a numbered subpattern match. We know that
        if a digit follows ( then there will just be digits until ) because
        the syntax was checked in the first pass. */

        else if ((digitab[ptr[1]] && ctype_digit) != 0)
          {
          int condref;                 /* Don't amalgamate; some compilers */
          condref = *(++ptr) - '0';    /* grumble at autoincrement in declaration */
          while (*(++ptr) != ')') condref = condref*10 + *ptr - '0';
          if (condref == 0)
            {
            *errorptr = ERR35;
            goto FAILED;
            }
          ptr++;
          code[1+LINK_SIZE] = OP_CREF;
          PUT2(code, 2+LINK_SIZE, condref);
          skipbytes = 3;
          }
        /* For conditions that are assertions, we just fall through, having
        set bravalue above. */
        break;

        case '=':                 /* Positive lookahead */
        bravalue = OP_ASSERT;
        ptr++;
        break;

        case '!':                 /* Negative lookahead */
        bravalue = OP_ASSERT_NOT;
        ptr++;
        break;

        case '<':                 /* Lookbehinds */
        switch (*(++ptr))
          {
          case '=':               /* Positive lookbehind */
          bravalue = OP_ASSERTBACK;
          ptr++;
          break;

          case '!':               /* Negative lookbehind */
          bravalue = OP_ASSERTBACK_NOT;
          ptr++;
          break;
          }
        break;

        case '>':                 /* One-time brackets */
        bravalue = OP_ONCE;
        ptr++;
        break;

        case 'C':                 /* Callout - may be followed by digits */
        *code++ = OP_CALLOUT;
          {
          int n = 0;
          while ((digitab[*(++ptr)] & ctype_digit) != 0)
            n = n * 10 + *ptr - '0';
          if (n > 255)
            {
            *errorptr = ERR38;
            goto FAILED;
            }
          *code++ = n;
          }
        previous = NULL;
        continue;

        case 'P':                 /* Named subpattern handling */
        if (*(++ptr) == '<')      /* Definition */
          {
          int i, namelen;
          uschar *slot = cd->name_table;
          const uschar *name;     /* Don't amalgamate; some compilers */
          name = ++ptr;           /* grumble at autoincrement in declaration */

          while (*ptr++ != '>');
          namelen = ptr - name - 1;

          for (i = 0; i < cd->names_found; i++)
            {
            int crc = memcmp(name, slot+2, namelen);
            if (crc == 0)
              {
              if (slot[2+namelen] == 0)
                {
                *errorptr = ERR43;
                goto FAILED;
                }
              crc = -1;             /* Current name is substring */
              }
            if (crc < 0)
              {
              memmove(slot + cd->name_entry_size, slot,
                (cd->names_found - i) * cd->name_entry_size);
              break;
              }
            slot += cd->name_entry_size;
            }

          PUT2(slot, 0, *brackets + 1);
          memcpy(slot + 2, name, namelen);
          slot[2+namelen] = 0;
          cd->names_found++;
          goto NUMBERED_GROUP;
          }

        if (*ptr == '=' || *ptr == '>')  /* Reference or recursion */
          {
          int i, namelen;
          int type = *ptr++;
          const uschar *name = ptr;
          uschar *slot = cd->name_table;

          while (*ptr != ')') ptr++;
          namelen = ptr - name;

          for (i = 0; i < cd->names_found; i++)
            {
            if (strncmp((char *)name, (char *)slot+2, namelen) == 0) break;
            slot += cd->name_entry_size;
            }
          if (i >= cd->names_found)
            {
            *errorptr = ERR15;
            goto FAILED;
            }

          recno = GET2(slot, 0);

          if (type == '>') goto HANDLE_RECURSION;  /* A few lines below */

          /* Back reference */

          previous = code;
          *code++ = OP_REF;
          PUT2INC(code, 0, recno);
          cd->backref_map |= (recno < 32)? (1 << recno) : 1;
          if (recno > cd->top_backref) cd->top_backref = recno;
          continue;
          }

        /* Should never happen */
        break;

        case 'R':                 /* Pattern recursion */
        ptr++;                    /* Same as (?0)      */
        /* Fall through */

        /* Recursion or "subroutine" call */

        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
          {
          const uschar *called;
          recno = 0;
          while((digitab[*ptr] & ctype_digit) != 0)
            recno = recno * 10 + *ptr++ - '0';

          /* Come here from code above that handles a named recursion */

          HANDLE_RECURSION:

          previous = code;

          /* Find the bracket that is being referenced. Temporarily end the
          regex in case it doesn't exist. */

          *code = OP_END;
          called = (recno == 0)?
            cd->start_code : find_bracket(cd->start_code, utf8, recno);

          if (called == NULL)
            {
            *errorptr = ERR15;
            goto FAILED;
            }

          /* If the subpattern is still open, this is a recursive call. We
          check to see if this is a left recursion that could loop for ever,
          and diagnose that case. */

          if (GET(called, 1) == 0 && could_be_empty(called, code, bcptr, utf8))
            {
            *errorptr = ERR40;
            goto FAILED;
            }

          /* Insert the recursion/subroutine item */

          *code = OP_RECURSE;
          PUT(code, 1, called - cd->start_code);
          code += 1 + LINK_SIZE;
          }
        continue;

        /* Character after (? not specially recognized */

        default:                  /* Option setting */
        set = unset = 0;
        optset = &set;

        while (*ptr != ')' && *ptr != ':')
          {
          switch (*ptr++)
            {
            case '-': optset = &unset; break;

            case 'i': *optset |= PCRE_CASELESS; break;
            case 'm': *optset |= PCRE_MULTILINE; break;
            case 's': *optset |= PCRE_DOTALL; break;
            case 'x': *optset |= PCRE_EXTENDED; break;
            case 'U': *optset |= PCRE_UNGREEDY; break;
            case 'X': *optset |= PCRE_EXTRA; break;
            }
          }

        /* Set up the changed option bits, but don't change anything yet. */

        newoptions = (options | set) & (~unset);

        /* If the options ended with ')' this is not the start of a nested
        group with option changes, so the options change at this level. Compile
        code to change the ims options if this setting actually changes any of
        them. We also pass the new setting back so that it can be put at the
        start of any following branches, and when this group ends (if we are in
        a group), a resetting item can be compiled.

        Note that if this item is right at the start of the pattern, the
        options will have been abstracted and made global, so there will be no
        change to compile. */

        if (*ptr == ')')
          {
          if ((options & PCRE_IMS) != (newoptions & PCRE_IMS))
            {
            *code++ = OP_OPT;
            *code++ = newoptions & PCRE_IMS;
            }

          /* Change options at this level, and pass them back for use
          in subsequent branches. Reset the greedy defaults and the case
          value for firstbyte and reqbyte. */

          *optionsptr = options = newoptions;
          greedy_default = ((newoptions & PCRE_UNGREEDY) != 0);
          greedy_non_default = greedy_default ^ 1;
          req_caseopt = ((options & PCRE_CASELESS) != 0)? REQ_CASELESS : 0;

          previous = NULL;       /* This item can't be repeated */
          continue;              /* It is complete */
          }

        /* If the options ended with ':' we are heading into a nested group
        with possible change of options. Such groups are non-capturing and are
        not assertions of any kind. All we need to do is skip over the ':';
        the newoptions value is handled below. */

        bravalue = OP_BRA;
        ptr++;
        }
      }

    /* If PCRE_NO_AUTO_CAPTURE is set, all unadorned brackets become
    non-capturing and behave like (?:...) brackets */

    else if ((options & PCRE_NO_AUTO_CAPTURE) != 0)
      {
      bravalue = OP_BRA;
      }

    /* Else we have a referencing group; adjust the opcode. If the bracket
    number is greater than EXTRACT_BASIC_MAX, we set the opcode one higher, and
    arrange for the true number to follow later, in an OP_BRANUMBER item. */

    else
      {
      NUMBERED_GROUP:
      if (++(*brackets) > EXTRACT_BASIC_MAX)
        {
        bravalue = OP_BRA + EXTRACT_BASIC_MAX + 1;
        code[1+LINK_SIZE] = OP_BRANUMBER;
        PUT2(code, 2+LINK_SIZE, *brackets);
        skipbytes = 3;
        }
      else bravalue = OP_BRA + *brackets;
      }

    /* Process nested bracketed re. Assertions may not be repeated, but other
    kinds can be. We copy code into a non-register variable in order to be able
    to pass its address because some compilers complain otherwise. Pass in a
    new setting for the ims options if they have changed. */

    previous = (bravalue >= OP_ONCE)? code : NULL;
    *code = bravalue;
    tempcode = code;
    tempreqvary = cd->req_varyopt;     /* Save value before bracket */

    if (!compile_regex(
         newoptions,                   /* The complete new option state */
         options & PCRE_IMS,           /* The previous ims option state */
         brackets,                     /* Extracting bracket count */
         &tempcode,                    /* Where to put code (updated) */
         &ptr,                         /* Input pointer (updated) */
         errorptr,                     /* Where to put an error message */
         (bravalue == OP_ASSERTBACK ||
          bravalue == OP_ASSERTBACK_NOT), /* TRUE if back assert */
         skipbytes,                    /* Skip over OP_COND/OP_BRANUMBER */
         &subfirstbyte,                /* For possible first char */
         &subreqbyte,                  /* For possible last char */
         bcptr,                        /* Current branch chain */
         cd))                          /* Tables block */
      goto FAILED;

    /* At the end of compiling, code is still pointing to the start of the
    group, while tempcode has been updated to point past the end of the group
    and any option resetting that may follow it. The pattern pointer (ptr)
    is on the bracket. */

    /* If this is a conditional bracket, check that there are no more than
    two branches in the group. */

    else if (bravalue == OP_COND)
      {
      uschar *tc = code;
      condcount = 0;

      do {
         condcount++;
         tc += GET(tc,1);
         }
      while (*tc != OP_KET);

      if (condcount > 2)
        {
        *errorptr = ERR27;
        goto FAILED;
        }

      /* If there is just one branch, we must not make use of its firstbyte or
      reqbyte, because this is equivalent to an empty second branch. */

      if (condcount == 1) subfirstbyte = subreqbyte = REQ_NONE;
      }

    /* Handle updating of the required and first characters. Update for normal
    brackets of all kinds, and conditions with two branches (see code above).
    If the bracket is followed by a quantifier with zero repeat, we have to
    back off. Hence the definition of zeroreqbyte and zerofirstbyte outside the
    main loop so that they can be accessed for the back off. */

    zeroreqbyte = reqbyte;
    zerofirstbyte = firstbyte;
    groupsetfirstbyte = FALSE;

    if (bravalue >= OP_BRA || bravalue == OP_ONCE || bravalue == OP_COND)
      {
      /* If we have not yet set a firstbyte in this branch, take it from the
      subpattern, remembering that it was set here so that a repeat of more
      than one can replicate it as reqbyte if necessary. If the subpattern has
      no firstbyte, set "none" for the whole branch. In both cases, a zero
      repeat forces firstbyte to "none". */

      if (firstbyte == REQ_UNSET)
        {
        if (subfirstbyte >= 0)
          {
          firstbyte = subfirstbyte;
          groupsetfirstbyte = TRUE;
          }
        else firstbyte = REQ_NONE;
        zerofirstbyte = REQ_NONE;
        }

      /* If firstbyte was previously set, convert the subpattern's firstbyte
      into reqbyte if there wasn't one, using the vary flag that was in
      existence beforehand. */

      else if (subfirstbyte >= 0 && subreqbyte < 0)
        subreqbyte = subfirstbyte | tempreqvary;

      /* If the subpattern set a required byte (or set a first byte that isn't
      really the first byte - see above), set it. */

      if (subreqbyte >= 0) reqbyte = subreqbyte;
      }

    /* For a forward assertion, we take the reqbyte, if set. This can be
    helpful if the pattern that follows the assertion doesn't set a different
    char. For example, it's useful for /(?=abcde).+/. We can't set firstbyte
    for an assertion, however because it leads to incorrect effect for patterns
    such as /(?=a)a.+/ when the "real" "a" would then become a reqbyte instead
    of a firstbyte. This is overcome by a scan at the end if there's no
    firstbyte, looking for an asserted first char. */

    else if (bravalue == OP_ASSERT && subreqbyte >= 0) reqbyte = subreqbyte;

    /* Now update the main code pointer to the end of the group. */

    code = tempcode;

    /* Error if hit end of pattern */

    if (*ptr != ')')
      {
      *errorptr = ERR14;
      goto FAILED;
      }
    break;

    /* Check \ for being a real metacharacter; if not, fall through and handle
    it as a data character at the start of a string. Escape items are checked
    for validity in the pre-compiling pass. */

    case '\\':
    tempptr = ptr;
    c = check_escape(&ptr, errorptr, *brackets, options, FALSE);

    /* Handle metacharacters introduced by \. For ones like \d, the ESC_ values
    are arranged to be the negation of the corresponding OP_values. For the
    back references, the values are ESC_REF plus the reference number. Only
    back references and those types that consume a character may be repeated.
    We can test for values between ESC_b and ESC_Z for the latter; this may
    have to change if any new ones are ever created. */

    if (c < 0)
      {
      if (-c == ESC_Q)            /* Handle start of quoted string */
        {
        if (ptr[1] == '\\' && ptr[2] == 'E') ptr += 2; /* avoid empty string */
          else inescq = TRUE;
        continue;
        }

      /* For metasequences that actually match a character, we disable the
      setting of a first character if it hasn't already been set. */

      if (firstbyte == REQ_UNSET && -c > ESC_b && -c < ESC_Z)
        firstbyte = REQ_NONE;

      /* Set values to reset to if this is followed by a zero repeat. */

      zerofirstbyte = firstbyte;
      zeroreqbyte = reqbyte;

      /* Back references are handled specially */

      if (-c >= ESC_REF)
        {
        int number = -c - ESC_REF;
        previous = code;
        *code++ = OP_REF;
        PUT2INC(code, 0, number);
        }
      else
        {
        previous = (-c > ESC_b && -c < ESC_Z)? code : NULL;
        *code++ = -c;
        }
      continue;
      }

    /* Data character: reset and fall through */

    ptr = tempptr;
    c = '\\';

    /* Handle a run of data characters until a metacharacter is encountered.
    The first character is guaranteed not to be whitespace or # when the
    extended flag is set. */

    NORMAL_CHAR:
    default:
    previous = code;
    *code = OP_CHARS;
    code += 2;
    length = 0;

    do
      {
      /* If in \Q...\E, check for the end; if not, we always have a literal */

      if (inescq)
        {
        if (c == '\\' && ptr[1] == 'E')
          {
          inescq = FALSE;
          ptr++;
          }
        else
          {
          *code++ = c;
          length++;
          }
        continue;
        }

      /* Skip white space and comments for /x patterns */

      if ((options & PCRE_EXTENDED) != 0)
        {
        if ((cd->ctypes[c] & ctype_space) != 0) continue;
        if (c == '#')
          {
          /* The space before the ; is to avoid a warning on a silly compiler
          on the Macintosh. */
          while ((c = *(++ptr)) != 0 && c != NEWLINE) ;
          if (c == 0) break;
          continue;
          }
        }

      /* Backslash may introduce a data char or a metacharacter. Escaped items
      are checked for validity in the pre-compiling pass. Stop the string
      before a metaitem. */

      if (c == '\\')
        {
        tempptr = ptr;
        c = check_escape(&ptr, errorptr, *brackets, options, FALSE);
        if (c < 0) { ptr = tempptr; break; }

        /* If a character is > 127 in UTF-8 mode, we have to turn it into
        two or more characters in the UTF-8 encoding. */

#ifdef SUPPORT_UTF8
        if (utf8 && c > 127)
          {
          uschar buffer[8];
          int len = ord2utf8(c, buffer);
          for (c = 0; c < len; c++) *code++ = buffer[c];
          length += len;
          continue;
          }
#endif
        }

      /* Ordinary character or single-char escape */

      *code++ = c;
      length++;
      }

    /* This "while" is the end of the "do" above. */

    while (length < MAXLIT && (cd->ctypes[c = *(++ptr)] & ctype_meta) == 0);

    /* Update the first and last requirements. These are always bytes, even in
    UTF-8 mode. However, there is a special case to be considered when there
    are only one or two characters. Because this gets messy in UTF-8 mode, the
    code is kept separate. When we get here "length" contains the number of
    bytes. */

#ifdef SUPPORT_UTF8
    if (utf8 && length > 1)
      {
      uschar *t = previous + 3;                      /* After this code, t */
      while (t < code && (*t & 0xc0) == 0x80) t++;   /* follows the 1st char */

      /* Handle the case when there is only one multibyte character. It must
      have at least two bytes because of the "length > 1" test above. */

      if (t == code)
        {
        /* If no previous first byte, set it from this character, but revert to
        none on a zero repeat. */

        if (firstbyte == REQ_UNSET)
          {
          zerofirstbyte = REQ_NONE;
          firstbyte = previous[2];
          }

        /* Otherwise, leave the first byte value alone, and don't change it on
        a zero repeat */

        else zerofirstbyte = firstbyte;

        /* In both cases, a zero repeat resets the previous required byte */

        zeroreqbyte = reqbyte;
        }

      /* Handle the case when there is more than one character. These may be
      single-byte or multibyte characters */

      else
        {
        t = code - 1;                       /* After this code, t is at the */
        while ((*t & 0xc0) == 0x80) t--;    /* start of the last character */

        /* If no previous first byte, set it from the first character, and
        retain it on a zero repeat (of the last character). The required byte
        is reset on a zero repeat, either to the byte before the last
        character, unless this is the first byte of the string. In that case,
        it reverts to its previous value. */

        if (firstbyte == REQ_UNSET)
          {
          zerofirstbyte = firstbyte = previous[2] | req_caseopt;
          zeroreqbyte = (t - 1 == previous + 2)?
            reqbyte : t[-1] | req_caseopt | cd->req_varyopt;
          }

        /* If there was a previous first byte, leave it alone, and don't change
        it on a zero repeat. The required byte is reset on a zero repeat to the
        byte before the last character. */

        else
          {
          zerofirstbyte = firstbyte;
          zeroreqbyte = t[-1] | req_caseopt | cd->req_varyopt;
          }
        }

      /* In all cases (we know length > 1), the new required byte is the last
      byte of the string. */

      reqbyte = code[-1] | req_caseopt | cd->req_varyopt;
      }

    else   /* End of UTF-8 coding */
#endif

    /* This is the code for non-UTF-8 operation, either without UTF-8 support,
    or when UTF-8 is not enabled. */

      {
      /* firstbyte was not previously set; take it from this string */

      if (firstbyte == REQ_UNSET)
        {
        if (length == 1)
          {
          zerofirstbyte = REQ_NONE;
          firstbyte = previous[2] | req_caseopt;
          zeroreqbyte = reqbyte;
          }
        else
          {
          zerofirstbyte = firstbyte = previous[2] | req_caseopt;
          zeroreqbyte = (length > 2)?
            (code[-2] | req_caseopt | cd->req_varyopt) : reqbyte;
          reqbyte = code[-1] | req_caseopt | cd->req_varyopt;
          }
        }

      /* firstbyte was previously set */

      else
        {
        zerofirstbyte = firstbyte;
        zeroreqbyte = (length == 1)? reqbyte :
          code[-2] | req_caseopt | cd->req_varyopt;
        reqbyte = code[-1] | req_caseopt | cd->req_varyopt;
        }
      }

    /* Set the length in the data vector, and advance to the next state. */

    previous[1] = length;
    if (length < MAXLIT) ptr--;
    break;
    }
  }                   /* end of big loop */

/* Control never reaches here by falling through, only by a goto for all the
error states. Pass back the position in the pattern so that it can be displayed
to the user for diagnosing the error. */

FAILED:
*ptrptr = ptr;
return FALSE;
}


/*************************************************
*     Compile sequence of alternatives           *
*************************************************/

/* On entry, ptr is pointing past the bracket character, but on return
it points to the closing bracket, or vertical bar, or end of string.
The code variable is pointing at the byte into which the BRA operator has been
stored. If the ims options are changed at the start (for a (?ims: group) or
during any branch, we need to insert an OP_OPT item at the start of every
following branch to ensure they get set correctly at run time, and also pass
the new options into every subsequent branch compile.

Argument:
  options        option bits, including any changes for this subpattern
  oldims         previous settings of ims option bits
  brackets       -> int containing the number of extracting brackets used
  codeptr        -> the address of the current code pointer
  ptrptr         -> the address of the current pattern pointer
  errorptr       -> pointer to error message
  lookbehind     TRUE if this is a lookbehind assertion
  skipbytes      skip this many bytes at start (for OP_COND, OP_BRANUMBER)
  firstbyteptr   place to put the first required character, or a negative number
  reqbyteptr     place to put the last required character, or a negative number
  bcptr          pointer to the chain of currently open branches
  cd             points to the data block with tables pointers etc.

Returns:      TRUE on success
*/

static BOOL
compile_regex(int options, int oldims, int *brackets, uschar **codeptr,
  const uschar **ptrptr, const char **errorptr, BOOL lookbehind, int skipbytes,
  int *firstbyteptr, int *reqbyteptr, branch_chain *bcptr, compile_data *cd)
{
const uschar *ptr = *ptrptr;
uschar *code = *codeptr;
uschar *last_branch = code;
uschar *start_bracket = code;
uschar *reverse_count = NULL;
int firstbyte, reqbyte;
int branchfirstbyte, branchreqbyte;
branch_chain bc;

bc.outer = bcptr;
bc.current = code;

firstbyte = reqbyte = REQ_UNSET;

/* Offset is set zero to mark that this bracket is still open */

PUT(code, 1, 0);
code += 1 + LINK_SIZE + skipbytes;

/* Loop for each alternative branch */

for (;;)
  {
  /* Handle a change of ims options at the start of the branch */

  if ((options & PCRE_IMS) != oldims)
    {
    *code++ = OP_OPT;
    *code++ = options & PCRE_IMS;
    }

  /* Set up dummy OP_REVERSE if lookbehind assertion */

  if (lookbehind)
    {
    *code++ = OP_REVERSE;
    reverse_count = code;
    PUTINC(code, 0, 0);
    }

  /* Now compile the branch */

  if (!compile_branch(&options, brackets, &code, &ptr, errorptr,
        &branchfirstbyte, &branchreqbyte, &bc, cd))
    {
    *ptrptr = ptr;
    return FALSE;
    }

  /* If this is the first branch, the firstbyte and reqbyte values for the
  branch become the values for the regex. */

  if (*last_branch != OP_ALT)
    {
    firstbyte = branchfirstbyte;
    reqbyte = branchreqbyte;
    }

  /* If this is not the first branch, the first char and reqbyte have to
  match the values from all the previous branches, except that if the previous
  value for reqbyte didn't have REQ_VARY set, it can still match, and we set
  REQ_VARY for the regex. */

  else
    {
    /* If we previously had a firstbyte, but it doesn't match the new branch,
    we have to abandon the firstbyte for the regex, but if there was previously
    no reqbyte, it takes on the value of the old firstbyte. */

    if (firstbyte >= 0 && firstbyte != branchfirstbyte)
      {
      if (reqbyte < 0) reqbyte = firstbyte;
      firstbyte = REQ_NONE;
      }

    /* If we (now or from before) have no firstbyte, a firstbyte from the
    branch becomes a reqbyte if there isn't a branch reqbyte. */

    if (firstbyte < 0 && branchfirstbyte >= 0 && branchreqbyte < 0)
        branchreqbyte = branchfirstbyte;

    /* Now ensure that the reqbytes match */

    if ((reqbyte & ~REQ_VARY) != (branchreqbyte & ~REQ_VARY))
      reqbyte = REQ_NONE;
    else reqbyte |= branchreqbyte;   /* To "or" REQ_VARY */
    }

  /* If lookbehind, check that this branch matches a fixed-length string,
  and put the length into the OP_REVERSE item. Temporarily mark the end of
  the branch with OP_END. */

  if (lookbehind)
    {
    int length;
    *code = OP_END;
    length = find_fixedlength(last_branch, options);
    DPRINTF(("fixed length = %d\n", length));
    if (length < 0)
      {
      *errorptr = (length == -2)? ERR36 : ERR25;
      *ptrptr = ptr;
      return FALSE;
      }
    PUT(reverse_count, 0, length);
    }

  /* Reached end of expression, either ')' or end of pattern. Go back through
  the alternative branches and reverse the chain of offsets, with the field in
  the BRA item now becoming an offset to the first alternative. If there are
  no alternatives, it points to the end of the group. The length in the
  terminating ket is always the length of the whole bracketed item. If any of
  the ims options were changed inside the group, compile a resetting op-code
  following, except at the very end of the pattern. Return leaving the pointer
  at the terminating char. */

  if (*ptr != '|')
    {
    int length = code - last_branch;
    do
      {
      int prev_length = GET(last_branch, 1);
      PUT(last_branch, 1, length);
      length = prev_length;
      last_branch -= length;
      }
    while (length > 0);

    /* Fill in the ket */

    *code = OP_KET;
    PUT(code, 1, code - start_bracket);
    code += 1 + LINK_SIZE;

    /* Resetting option if needed */

    if ((options & PCRE_IMS) != oldims && *ptr == ')')
      {
      *code++ = OP_OPT;
      *code++ = oldims;
      }

    /* Set values to pass back */

    *codeptr = code;
    *ptrptr = ptr;
    *firstbyteptr = firstbyte;
    *reqbyteptr = reqbyte;
    return TRUE;
    }

  /* Another branch follows; insert an "or" node. Its length field points back
  to the previous branch while the bracket remains open. At the end the chain
  is reversed. It's done like this so that the start of the bracket has a
  zero offset until it is closed, making it possible to detect recursion. */

  *code = OP_ALT;
  PUT(code, 1, code - last_branch);
  bc.current = last_branch = code;
  code += 1 + LINK_SIZE;
  ptr++;
  }
/* Control never reaches here */
}


/*************************************************
*          Check for anchored expression         *
*************************************************/

/* Try to find out if this is an anchored regular expression. Consider each
alternative branch. If they all start with OP_SOD or OP_CIRC, or with a bracket
all of whose alternatives start with OP_SOD or OP_CIRC (recurse ad lib), then
it's anchored. However, if this is a multiline pattern, then only OP_SOD
counts, since OP_CIRC can match in the middle.

We can also consider a regex to be anchored if OP_SOM starts all its branches.
This is the code for \G, which means "match at start of match position, taking
into account the match offset".

A branch is also implicitly anchored if it starts with .* and DOTALL is set,
because that will try the rest of the pattern at all possible matching points,
so there is no point trying again.... er ....

.... except when the .* appears inside capturing parentheses, and there is a
subsequent back reference to those parentheses. We haven't enough information
to catch that case precisely.

At first, the best we could do was to detect when .* was in capturing brackets
and the highest back reference was greater than or equal to that level.
However, by keeping a bitmap of the first 31 back references, we can catch some
of the more common cases more precisely.

Arguments:
  code           points to start of expression (the bracket)
  options        points to the options setting
  bracket_map    a bitmap of which brackets we are inside while testing; this
                  handles up to substring 31; after that we just have to take
                  the less precise approach
  backref_map    the back reference bitmap

Returns:     TRUE or FALSE
*/

static BOOL
is_anchored(register const uschar *code, int *options, unsigned int bracket_map,
  unsigned int backref_map)
{
do {
   const uschar *scode =
     first_significant_code(code + 1+LINK_SIZE, options, PCRE_MULTILINE);
   register int op = *scode;

   /* Capturing brackets */

   if (op > OP_BRA)
     {
     int new_map;
     op -= OP_BRA;
     if (op > EXTRACT_BASIC_MAX) op = GET2(scode, 2+LINK_SIZE);
     new_map = bracket_map | ((op < 32)? (1 << op) : 1);
     if (!is_anchored(scode, options, new_map, backref_map)) return FALSE;
     }

   /* Other brackets */

   else if (op == OP_BRA || op == OP_ASSERT || op == OP_ONCE || op == OP_COND)
     {
     if (!is_anchored(scode, options, bracket_map, backref_map)) return FALSE;
     }

   /* .* is not anchored unless DOTALL is set and it isn't in brackets that
   are or may be referenced. */

   else if ((op == OP_TYPESTAR || op == OP_TYPEMINSTAR) &&
            (*options & PCRE_DOTALL) != 0)
     {
     if (scode[1] != OP_ANY || (bracket_map & backref_map) != 0) return FALSE;
     }

   /* Check for explicit anchoring */

   else if (op != OP_SOD && op != OP_SOM &&
           ((*options & PCRE_MULTILINE) != 0 || op != OP_CIRC))
     return FALSE;
   code += GET(code, 1);
   }
while (*code == OP_ALT);   /* Loop for each alternative */
return TRUE;
}


/*************************************************
*         Check for starting with ^ or .*        *
*************************************************/

/* This is called to find out if every branch starts with ^ or .* so that
"first char" processing can be done to speed things up in multiline
matching and for non-DOTALL patterns that start with .* (which must start at
the beginning or after \n). As in the case of is_anchored() (see above), we
have to take account of back references to capturing brackets that contain .*
because in that case we can't make the assumption.

Arguments:
  code           points to start of expression (the bracket)
  bracket_map    a bitmap of which brackets we are inside while testing; this
                  handles up to substring 31; after that we just have to take
                  the less precise approach
  backref_map    the back reference bitmap

Returns:         TRUE or FALSE
*/

static BOOL
is_startline(const uschar *code, unsigned int bracket_map,
  unsigned int backref_map)
{
do {
   const uschar *scode = first_significant_code(code + 1+LINK_SIZE, NULL, 0);
   register int op = *scode;

   /* Capturing brackets */

   if (op > OP_BRA)
     {
     int new_map;
     op -= OP_BRA;
     if (op > EXTRACT_BASIC_MAX) op = GET2(scode, 2+LINK_SIZE);
     new_map = bracket_map | ((op < 32)? (1 << op) : 1);
     if (!is_startline(scode, new_map, backref_map)) return FALSE;
     }

   /* Other brackets */

   else if (op == OP_BRA || op == OP_ASSERT || op == OP_ONCE || op == OP_COND)
     { if (!is_startline(scode, bracket_map, backref_map)) return FALSE; }

   /* .* is not anchored unless DOTALL is set and it isn't in brackets that
   may be referenced. */

   else if (op == OP_TYPESTAR || op == OP_TYPEMINSTAR)
     {
     if (scode[1] != OP_ANY || (bracket_map & backref_map) != 0) return FALSE;
     }

   /* Check for explicit circumflex */

   else if (op != OP_CIRC) return FALSE;
   code += GET(code, 1);
   }
while (*code == OP_ALT);  /* Loop for each alternative */
return TRUE;
}


/*************************************************
*       Check for asserted fixed first char      *
*************************************************/

/* During compilation, the "first char" settings from forward assertions are
discarded, because they can cause conflicts with actual literals that follow.
However, if we end up without a first char setting for an unanchored pattern,
it is worth scanning the regex to see if there is an initial asserted first
char. If all branches start with the same asserted char, or with a bracket all
of whose alternatives start with the same asserted char (recurse ad lib), then
we return that char, otherwise -1.

Arguments:
  code       points to start of expression (the bracket)
  options    pointer to the options (used to check casing changes)
  inassert   TRUE if in an assertion

Returns:     -1 or the fixed first char
*/

static int
find_firstassertedchar(const uschar *code, int *options, BOOL inassert)
{
register int c = -1;
do {
   int d;
   const uschar *scode =
     first_significant_code(code + 1+LINK_SIZE, options, PCRE_CASELESS);
   register int op = *scode;

   if (op >= OP_BRA) op = OP_BRA;

   switch(op)
     {
     default:
     return -1;

     case OP_BRA:
     case OP_ASSERT:
     case OP_ONCE:
     case OP_COND:
     if ((d = find_firstassertedchar(scode, options, op == OP_ASSERT)) < 0)
       return -1;
     if (c < 0) c = d; else if (c != d) return -1;
     break;

     case OP_EXACT:       /* Fall through */
     scode++;

     case OP_CHARS:       /* Fall through */
     scode++;

     case OP_PLUS:
     case OP_MINPLUS:
     if (!inassert) return -1;
     if (c < 0)
       {
       c = scode[1];
       if ((*options & PCRE_CASELESS) != 0) c |= REQ_CASELESS;
       }
     else if (c != scode[1]) return -1;
     break;
     }

   code += GET(code, 1);
   }
while (*code == OP_ALT);
return c;
}


#ifdef SUPPORT_UTF8
/*************************************************
*         Validate a UTF-8 string                *
*************************************************/

/* This function is called (optionally) at the start of compile or match, to
validate that a supposed UTF-8 string is actually valid. The early check means
that subsequent code can assume it is dealing with a valid string. The check
can be turned off for maximum performance, but then consequences of supplying
an invalid string are then undefined.

Arguments:
  string       points to the string
  length       length of string, or -1 if the string is zero-terminated

Returns:       < 0    if the string is a valid UTF-8 string
               >= 0   otherwise; the value is the offset of the bad byte
*/

static int
valid_utf8(const uschar *string, int length)
{
register const uschar *p;

if (length < 0)
  {
  for (p = string; *p != 0; p++);
  length = p - string;
  }

for (p = string; length-- > 0; p++)
  {
  int ab;
  if (*p < 128) continue;
  if ((*p & 0xc0) != 0xc0) return p - string;
  ab = utf8_table4[*p & 0x3f];  /* Number of additional bytes */
  if (length < ab) return p - string;
  while (ab-- > 0)
    {
    if ((*(++p) & 0xc0) != 0x80) return p - string;
    length--;
    }
  }

return -1;
}
#endif


/*************************************************
*        Compile a Regular Expression            *
*************************************************/

/* This function takes a string and returns a pointer to a block of store
holding a compiled version of the expression.

Arguments:
  pattern      the regular expression
  options      various option bits
  errorptr     pointer to pointer to error text
  erroroffset  ptr offset in pattern where error was detected
  tables       pointer to character tables or NULL

Returns:       pointer to compiled data block, or NULL on error,
               with errorptr and erroroffset set
*/

pcre *
pcre_compile(const char *pattern, int options, const char **errorptr,
  int *erroroffset, const unsigned char *tables)
{
real_pcre *re;
int length = 1 + LINK_SIZE;      /* For initial BRA plus length */
int runlength;
int c, firstbyte, reqbyte;
int bracount = 0;
int branch_extra = 0;
int branch_newextra;
int item_count = -1;
int name_count = 0;
int max_name_size = 0;
#ifdef SUPPORT_UTF8
int lastcharlength = 0;
BOOL utf8;
BOOL class_utf8;
#endif
BOOL inescq = FALSE;
unsigned int brastackptr = 0;
size_t size;
uschar *code;
const uschar *codestart;
const uschar *ptr;
compile_data compile_block;
int brastack[BRASTACK_SIZE];
uschar bralenstack[BRASTACK_SIZE];

/* We can't pass back an error message if errorptr is NULL; I guess the best we
can do is just return NULL. */

if (errorptr == NULL) return NULL;
*errorptr = NULL;

/* However, we can give a message for this error */

if (erroroffset == NULL)
  {
  *errorptr = ERR16;
  return NULL;
  }
*erroroffset = 0;

/* Can't support UTF8 unless PCRE has been compiled to include the code. */

#ifdef SUPPORT_UTF8
utf8 = (options & PCRE_UTF8) != 0;
if (utf8 && (options & PCRE_NO_UTF8_CHECK) == 0 &&
     (*erroroffset = valid_utf8((uschar *)pattern, -1)) >= 0)
  {
  *errorptr = ERR44;
  return NULL;
  }
#else
if ((options & PCRE_UTF8) != 0)
  {
  *errorptr = ERR32;
  return NULL;
  }
#endif

if ((options & ~PUBLIC_OPTIONS) != 0)
  {
  *errorptr = ERR17;
  return NULL;
  }

/* Set up pointers to the individual character tables */

if (tables == NULL) tables = pcre_default_tables;
compile_block.lcc = tables + lcc_offset;
compile_block.fcc = tables + fcc_offset;
compile_block.cbits = tables + cbits_offset;
compile_block.ctypes = tables + ctypes_offset;

/* Maximum back reference and backref bitmap. This is updated for numeric
references during the first pass, but for named references during the actual
compile pass. The bitmap records up to 31 back references to help in deciding
whether (.*) can be treated as anchored or not. */

compile_block.top_backref = 0;
compile_block.backref_map = 0;

/* Reflect pattern for debugging output */

DPRINTF(("------------------------------------------------------------------\n"));
DPRINTF(("%s\n", pattern));

/* The first thing to do is to make a pass over the pattern to compute the
amount of store required to hold the compiled code. This does not have to be
perfect as long as errors are overestimates. At the same time we can detect any
flag settings right at the start, and extract them. Make an attempt to correct
for any counted white space if an "extended" flag setting appears late in the
pattern. We can't be so clever for #-comments. */

ptr = (const uschar *)(pattern - 1);
while ((c = *(++ptr)) != 0)
  {
  int min, max;
  int class_optcount;
  int bracket_length;
  int duplength;

  /* If we are inside a \Q...\E sequence, all chars are literal */

  if (inescq) goto NORMAL_CHAR;

  /* Otherwise, first check for ignored whitespace and comments */

  if ((options & PCRE_EXTENDED) != 0)
    {
    if ((compile_block.ctypes[c] & ctype_space) != 0) continue;
    if (c == '#')
      {
      /* The space before the ; is to avoid a warning on a silly compiler
      on the Macintosh. */
      while ((c = *(++ptr)) != 0 && c != NEWLINE) ;
      if (c == 0) break;
      continue;
      }
    }

  item_count++;    /* Is zero for the first non-comment item */

  switch(c)
    {
    /* A backslashed item may be an escaped "normal" character or a
    character type. For a "normal" character, put the pointers and
    character back so that tests for whitespace etc. in the input
    are done correctly. */

    case '\\':
      {
      const uschar *save_ptr = ptr;
      c = check_escape(&ptr, errorptr, bracount, options, FALSE);
      if (*errorptr != NULL) goto PCRE_ERROR_RETURN;
      if (c >= 0)
        {
        ptr = save_ptr;
        c = '\\';
        goto NORMAL_CHAR;
        }
      }

    /* If \Q, enter "literal" mode */

    if (-c == ESC_Q)
      {
      inescq = TRUE;
      continue;
      }

    /* Other escapes need one byte, and are of length one for repeats */

    length++;
#ifdef SUPPORT_UTF8
    lastcharlength = 1;
#endif

    /* A back reference needs an additional 2 bytes, plus either one or 5
    bytes for a repeat. We also need to keep the value of the highest
    back reference. */

    if (c <= -ESC_REF)
      {
      int refnum = -c - ESC_REF;
      compile_block.backref_map |= (refnum < 32)? (1 << refnum) : 1;
      if (refnum > compile_block.top_backref)
        compile_block.top_backref = refnum;
      length += 2;   /* For single back reference */
      if (ptr[1] == '{' && is_counted_repeat(ptr+2))
        {
        ptr = read_repeat_counts(ptr+2, &min, &max, errorptr);
        if (*errorptr != NULL) goto PCRE_ERROR_RETURN;
        if ((min == 0 && (max == 1 || max == -1)) ||
          (min == 1 && max == -1))
            length++;
        else length += 5;
        if (ptr[1] == '?') ptr++;
        }
      }
    continue;

    case '^':     /* Single-byte metacharacters */
    case '.':
    case '$':
    length++;
#ifdef SUPPORT_UTF8
    lastcharlength = 1;
#endif
    continue;

    case '*':            /* These repeats won't be after brackets; */
    case '+':            /* those are handled separately */
    case '?':
    length++;
    goto POSESSIVE;      /* A few lines below */

    /* This covers the cases of braced repeats after a single char, metachar,
    class, or back reference. */

    case '{':
    if (!is_counted_repeat(ptr+1)) goto NORMAL_CHAR;
    ptr = read_repeat_counts(ptr+1, &min, &max, errorptr);
    if (*errorptr != NULL) goto PCRE_ERROR_RETURN;

    /* These special cases just insert one extra opcode */

    if ((min == 0 && (max == 1 || max == -1)) ||
      (min == 1 && max == -1))
        length++;

    /* These cases might insert additional copies of a preceding character. */

    else
      {
#ifdef SUPPORT_UTF8
      /* In UTF-8 mode, we should find the length in lastcharlength */
      if (utf8)
        {
        if (min != 1)
          {
          length -= lastcharlength;   /* Uncount the original char or metachar */
          if (min > 0) length += 3 + lastcharlength;
          }
        length += lastcharlength + ((max > 0)? 3 : 1);
        }
      else
#endif

      /* Not UTF-8 mode: all characters are one byte */
        {
        if (min != 1)
          {
          length--;   /* Uncount the original char or metachar */
          if (min > 0) length += 4;
          }

        length += (max > 0)? 4 : 2;
        }
      }

    if (ptr[1] == '?') ptr++;      /* Needs no extra length */

    POSESSIVE:                     /* Test for possessive quantifier */
    if (ptr[1] == '+')
      {
      ptr++;
      length += 2 + 2*LINK_SIZE;   /* Allow for atomic brackets */
      }
    continue;

    /* An alternation contains an offset to the next branch or ket. If any ims
    options changed in the previous branch(es), and/or if we are in a
    lookbehind assertion, extra space will be needed at the start of the
    branch. This is handled by branch_extra. */