doc/html/pcrejit.html

<html>
<head>
<title>pcrejit specification</title>
</head>
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
<h1>pcrejit man page</h1>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
<p>
This page is part of the PCRE HTML documentation. It was generated automatically
from the original man page. If there is any nonsense in it, please consult the
man page, in case the conversion went wrong.
<br>
<ul>
<li><a name="TOC1" href="#SEC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a>
<li><a name="TOC2" href="#SEC2">AVAILABILITY OF JIT SUPPORT</a>
<li><a name="TOC3" href="#SEC3">SIMPLE USE OF JIT</a>
<li><a name="TOC4" href="#SEC4">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a>
<li><a name="TOC5" href="#SEC5">RETURN VALUES FROM JIT EXECUTION</a>
<li><a name="TOC6" href="#SEC6">SAVING AND RESTORING COMPILED PATTERNS</a>
<li><a name="TOC7" href="#SEC7">CONTROLLING THE JIT STACK</a>
<li><a name="TOC8" href="#SEC8">EXAMPLE CODE</a>
<li><a name="TOC9" href="#SEC9">SEE ALSO</a>
<li><a name="TOC10" href="#SEC10">AUTHOR</a>
<li><a name="TOC11" href="#SEC11">REVISION</a>
</ul>
<br><a name="SEC1" href="#TOC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a><br>
<P>
Just-in-time compiling is a heavyweight optimization that can greatly speed up
pattern matching. However, it comes at the cost of extra processing before the
match is performed. Therefore, it is of most benefit when the same pattern is
going to be matched many times. This does not necessarily mean many calls of
\fPpcre_exec()\fP; if the pattern is not anchored, matching attempts may take
place many times at various positions in the subject, even for a single call to
<b>pcre_exec()</b>. If the subject string is very long, it may still pay to use
JIT for one-off matches.
</P>
<P>
JIT support applies only to the traditional matching function,
<b>pcre_exec()</b>. It does not apply when <b>pcre_dfa_exec()</b> is being used.
The code for this support was written by Zoltan Herczeg.
</P>
<br><a name="SEC2" href="#TOC1">AVAILABILITY OF JIT SUPPORT</a><br>
<P>
JIT support is an optional feature of PCRE. The "configure" option --enable-jit
(or equivalent CMake option) must be set when PCRE is built if you want to use
JIT. The support is limited to the following hardware platforms:
<pre>
  ARM v5, v7, and Thumb2
  Intel x86 32-bit and 64-bit
  MIPS 32-bit
  Power PC 32-bit and 64-bit (experimental)
</pre>
The Power PC support is designated as experimental because it has not been
fully tested. If --enable-jit is set on an unsupported platform, compilation
fails.
</P>
<P>
A program can tell if JIT support is available by calling <b>pcre_config()</b>
with the PCRE_CONFIG_JIT option. The result is 1 when JIT is available, and 0
otherwise. However, a simple program does not need to check this in order to
use JIT. The API is implemented in a way that falls back to the ordinary PCRE
code if JIT is not available.
</P>
<br><a name="SEC3" href="#TOC1">SIMPLE USE OF JIT</a><br>
<P>
You have to do two things to make use of the JIT support in the simplest way:
<pre>
  (1) Call <b>pcre_study()</b> with the PCRE_STUDY_JIT_COMPILE option for
      each compiled pattern, and pass the resulting <b>pcre_extra</b> block to
      <b>pcre_exec()</b>.

  (2) Use <b>pcre_free_study()</b> to free the <b>pcre_extra</b> block when it is
      no longer needed instead of just freeing it yourself. This
      ensures that any JIT data is also freed.
</pre>
In some circumstances you may need to call additional functions. These are
described in the section entitled
<a href="#stackcontrol">"Controlling the JIT stack"</a>
below.
</P>
<P>
If JIT support is not available, PCRE_STUDY_JIT_COMPILE is ignored, and no JIT
data is set up. Otherwise, the compiled pattern is passed to the JIT compiler,
which turns it into machine code that executes much faster than the normal
interpretive code. When <b>pcre_exec()</b> is passed a <b>pcre_extra</b> block
containing a pointer to JIT code, it obeys that instead of the normal code. The
result is identical, but the code runs much faster.
</P>
<P>
There are some <b>pcre_exec()</b> options that are not supported for JIT
execution. There are also some pattern items that JIT cannot handle. Details
are given below. In both cases, execution automatically falls back to the
interpretive code.
</P>
<P>
If the JIT compiler finds an unsupported item, no JIT data is generated. You
can find out if JIT execution is available after studying a pattern by calling
<b>pcre_fullinfo()</b> with the PCRE_INFO_JIT option. A result of 1 means that
JIT compilation was successful. A result of 0 means that JIT support is not
available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE, or the
JIT compiler was not able to handle the pattern.
</P>
<P>
Once a pattern has been studied, with or without JIT, it can be used as many
times as you like for matching different subject strings.
</P>
<br><a name="SEC4" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br>
<P>
The only <b>pcre_exec()</b> options that are supported for JIT execution are
PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and
PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is not
supported.
</P>
<P>
The unsupported pattern items are:
<pre>
  \C            match a single byte; not supported in UTF-8 mode
  (?Cn)          callouts
  (?(&#60;name&#62;)...  conditional test on setting of a named subpattern
  (?(R)...       conditional test on whole pattern recursion
  (?(Rn)...      conditional test on recursion, by number
  (?(R&name)...  conditional test on recursion, by name
  (*COMMIT)      )
  (*MARK)        )
  (*PRUNE)       ) the backtracking control verbs
  (*SKIP)        )
  (*THEN)        )
</pre>
Support for some of these may be added in future.
</P>
<br><a name="SEC5" href="#TOC1">RETURN VALUES FROM JIT EXECUTION</a><br>
<P>
When a pattern is matched using JIT execution, the return values are the same
as those given by the interpretive <b>pcre_exec()</b> code, with the addition of
one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means that the memory used
for the JIT stack was insufficient. See
<a href="#stackcontrol">"Controlling the JIT stack"</a>
below for a discussion of JIT stack usage. For compatibility with the
interpretive <b>pcre_exec()</b> code, no more than two-thirds of the
<i>ovector</i> argument is used for passing back captured substrings.
</P>
<P>
The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if searching a
very large pattern tree goes on for too long, as it is in the same circumstance
when JIT is not used, but the details of exactly what is counted are not the
same. The PCRE_ERROR_RECURSIONLIMIT error code is never returned by JIT
execution.
</P>
<br><a name="SEC6" href="#TOC1">SAVING AND RESTORING COMPILED PATTERNS</a><br>
<P>
The code that is generated by the JIT compiler is architecture-specific, and is
also position dependent. For those reasons it cannot be saved (in a file or
database) and restored later like the bytecode and other data of a compiled
pattern. Saving and restoring compiled patterns is not something many people
do. More detail about this facility is given in the
<a href="pcreprecompile.html"><b>pcreprecompile</b></a>
documentation. It should be possible to run <b>pcre_study()</b> on a saved and
restored pattern, and thereby recreate the JIT data, but because JIT
compilation uses significant resources, it is probably not worth doing this;
you might as well recompile the original pattern.
<a name="stackcontrol"></a></P>
<br><a name="SEC7" href="#TOC1">CONTROLLING THE JIT STACK</a><br>
<P>
When the compiled JIT code runs, it needs a block of memory to use as a stack.
By default, it uses 32K on the machine stack. However, some large or
complicated patterns need more than this. The error PCRE_ERROR_JIT_STACKLIMIT
is given when there is not enough stack. Three functions are provided for
managing blocks of memory for use as JIT stacks.
</P>
<P>
The <b>pcre_jit_stack_alloc()</b> function creates a JIT stack. Its arguments
are a starting size and a maximum size, and it returns a pointer to an opaque
structure of type <b>pcre_jit_stack</b>, or NULL if there is an error. The
<b>pcre_jit_stack_free()</b> function can be used to free a stack that is no
longer needed. (For the technically minded: the address space is allocated by
mmap or VirtualAlloc.)
</P>
<P>
JIT uses far less memory for recursion than the interpretive code,
and a maximum stack size of 512K to 1M should be more than enough for any
pattern.
</P>
<P>
The <b>pcre_assign_jit_stack()</b> function specifies which stack JIT code
should use. Its arguments are as follows:
<pre>
  pcre_extra         *extra
  pcre_jit_callback  callback
  void               *data
</pre>
The <i>extra</i> argument must be the result of studying a pattern with
PCRE_STUDY_JIT_COMPILE. There are three cases for the values of the other two
options:
<pre>
  (1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block
      on the machine stack is used.

  (2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be
      a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>.

  (3) If <i>callback</i> not NULL, it must point to a function that is called
      with <i>data</i> as an argument at the start of matching, in order to
      set up a JIT stack. If the result is NULL, the internal 32K stack
      is used; otherwise the return value must be a valid JIT stack,
      the result of calling <b>pcre_jit_stack_alloc()</b>.
</pre>
You may safely assign the same JIT stack to more than one pattern, as long as
they are all matched sequentially in the same thread. In a multithread
application, each thread must use its own JIT stack.
</P>
<P>
Strictly speaking, even more is allowed. You can assign the same stack to any
number of patterns as long as they are not used for matching by multiple
threads at the same time. For example, you can assign the same stack to all
compiled patterns, and use a global mutex in the callback to wait until the
stack is available for use. However, this is an inefficient solution, and
not recommended.
</P>
<P>
This is a suggestion for how a typical multithreaded program might operate:
<pre>
  During thread initalization
    thread_local_var = pcre_jit_stack_alloc(...)

  During thread exit
    pcre_jit_stack_free(thread_local_var)

  Use a one-line callback function
    return thread_local_var
</pre>
All the functions described in this section do nothing if JIT is not available,
and <b>pcre_assign_jit_stack()</b> does nothing unless the <b>extra</b> argument
is non-NULL and points to a <b>pcre_extra</b> block that is the result of a
successful study with PCRE_STUDY_JIT_COMPILE.
</P>
<br><a name="SEC8" href="#TOC1">EXAMPLE CODE</a><br>
<P>
This is a single-threaded example that specifies a JIT stack without using a
callback.
<pre>
  int rc;
  int ovector[30];
  pcre *re;
  pcre_extra *extra;
  pcre_jit_stack *jit_stack;

  re = pcre_compile(pattern, 0, &error, &erroffset, NULL);
  /* Check for errors */
  extra = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &error);
  jit_stack = pcre_jit_stack_alloc(32*1024, 512*1024);
  /* Check for error (NULL) */
  pcre_assign_jit_stack(extra, NULL, jit_stack);
  rc = pcre_exec(re, extra, subject, length, 0, 0, ovector, 30);
  /* Check results */
  pcre_free(re);
  pcre_free_study(extra);
  pcre_jit_stack_free(jit_stack);

</PRE>
</P>
<br><a name="SEC9" href="#TOC1">SEE ALSO</a><br>
<P>
<b>pcreapi</b>(3)
</P>
<br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
<P>
Philip Hazel
<br>
University Computing Service
<br>
Cambridge CB2 3QH, England.
<br>
</P>
<br><a name="SEC11" href="#TOC1">REVISION</a><br>
<P>
Last updated: 19 October 2011
<br>
Copyright &copy; 1997-2011 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
1	ph10	678	<html>
2			<head>
3			<title>pcrejit specification</title>
4			</head>
5			<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6			<h1>pcrejit man page</h1>
7			<p>
8			Return to the <a href="index.html">PCRE index page</a>.
9			</p>
10			<p>
11			This page is part of the PCRE HTML documentation. It was generated automatically
12			from the original man page. If there is any nonsense in it, please consult the
13			man page, in case the conversion went wrong.
14			<br>
15			<ul>
16	ph10	691	<li><a name="TOC1" href="#SEC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a>
17			<li><a name="TOC2" href="#SEC2">AVAILABILITY OF JIT SUPPORT</a>
18			<li><a name="TOC3" href="#SEC3">SIMPLE USE OF JIT</a>
19			<li><a name="TOC4" href="#SEC4">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a>
20			<li><a name="TOC5" href="#SEC5">RETURN VALUES FROM JIT EXECUTION</a>
21			<li><a name="TOC6" href="#SEC6">SAVING AND RESTORING COMPILED PATTERNS</a>
22			<li><a name="TOC7" href="#SEC7">CONTROLLING THE JIT STACK</a>
23	ph10	835	<li><a name="TOC8" href="#SEC8">EXAMPLE CODE</a>
24			<li><a name="TOC9" href="#SEC9">SEE ALSO</a>
25			<li><a name="TOC10" href="#SEC10">AUTHOR</a>
26			<li><a name="TOC11" href="#SEC11">REVISION</a>
27	ph10	678	</ul>
28	ph10	691	<br><a name="SEC1" href="#TOC1">PCRE JUST-IN-TIME COMPILER SUPPORT</a><br>
29			<P>
30			Just-in-time compiling is a heavyweight optimization that can greatly speed up
31			pattern matching. However, it comes at the cost of extra processing before the
32			match is performed. Therefore, it is of most benefit when the same pattern is
33			going to be matched many times. This does not necessarily mean many calls of
34			\fPpcre_exec()\fP; if the pattern is not anchored, matching attempts may take
35			place many times at various positions in the subject, even for a single call to
36			<b>pcre_exec()</b>. If the subject string is very long, it may still pay to use
37			JIT for one-off matches.
38			</P>
39			<P>
40			JIT support applies only to the traditional matching function,
41			<b>pcre_exec()</b>. It does not apply when <b>pcre_dfa_exec()</b> is being used.
42			The code for this support was written by Zoltan Herczeg.
43			</P>
44			<br><a name="SEC2" href="#TOC1">AVAILABILITY OF JIT SUPPORT</a><br>
45			<P>
46			JIT support is an optional feature of PCRE. The "configure" option --enable-jit
47			(or equivalent CMake option) must be set when PCRE is built if you want to use
48			JIT. The support is limited to the following hardware platforms:
49			<pre>
50			ARM v5, v7, and Thumb2
51			Intel x86 32-bit and 64-bit
52			MIPS 32-bit
53	ph10	733	Power PC 32-bit and 64-bit (experimental)
54	ph10	691	</pre>
55	ph10	733	The Power PC support is designated as experimental because it has not been
56			fully tested. If --enable-jit is set on an unsupported platform, compilation
57			fails.
58	ph10	691	</P>
59			<P>
60	ph10	835	A program can tell if JIT support is available by calling <b>pcre_config()</b>
61			with the PCRE_CONFIG_JIT option. The result is 1 when JIT is available, and 0
62			otherwise. However, a simple program does not need to check this in order to
63			use JIT. The API is implemented in a way that falls back to the ordinary PCRE
64			code if JIT is not available.
65	ph10	691	</P>
66			<br><a name="SEC3" href="#TOC1">SIMPLE USE OF JIT</a><br>
67			<P>
68			You have to do two things to make use of the JIT support in the simplest way:
69			<pre>
70			(1) Call <b>pcre_study()</b> with the PCRE_STUDY_JIT_COMPILE option for
71			each compiled pattern, and pass the resulting <b>pcre_extra</b> block to
72			<b>pcre_exec()</b>.
73
74			(2) Use <b>pcre_free_study()</b> to free the <b>pcre_extra</b> block when it is
75			no longer needed instead of just freeing it yourself. This
76			ensures that any JIT data is also freed.
77			</pre>
78			In some circumstances you may need to call additional functions. These are
79			described in the section entitled
80			<a href="#stackcontrol">"Controlling the JIT stack"</a>
81			below.
82			</P>
83			<P>
84			If JIT support is not available, PCRE_STUDY_JIT_COMPILE is ignored, and no JIT
85			data is set up. Otherwise, the compiled pattern is passed to the JIT compiler,
86			which turns it into machine code that executes much faster than the normal
87			interpretive code. When <b>pcre_exec()</b> is passed a <b>pcre_extra</b> block
88			containing a pointer to JIT code, it obeys that instead of the normal code. The
89			result is identical, but the code runs much faster.
90			</P>
91			<P>
92			There are some <b>pcre_exec()</b> options that are not supported for JIT
93			execution. There are also some pattern items that JIT cannot handle. Details
94			are given below. In both cases, execution automatically falls back to the
95			interpretive code.
96			</P>
97			<P>
98			If the JIT compiler finds an unsupported item, no JIT data is generated. You
99			can find out if JIT execution is available after studying a pattern by calling
100			<b>pcre_fullinfo()</b> with the PCRE_INFO_JIT option. A result of 1 means that
101	ph10	708	JIT compilation was successful. A result of 0 means that JIT support is not
102	ph10	691	available, or the pattern was not studied with PCRE_STUDY_JIT_COMPILE, or the
103			JIT compiler was not able to handle the pattern.
104			</P>
105	ph10	708	<P>
106			Once a pattern has been studied, with or without JIT, it can be used as many
107			times as you like for matching different subject strings.
108			</P>
109	ph10	691	<br><a name="SEC4" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br>
110			<P>
111			The only <b>pcre_exec()</b> options that are supported for JIT execution are
112			PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and
113			PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is not
114			supported.
115			</P>
116			<P>
117			The unsupported pattern items are:
118			<pre>
119	ph10	835	\C match a single byte; not supported in UTF-8 mode
120	ph10	691	(?Cn) callouts
121	ph10	835	(?(<name>)... conditional test on setting of a named subpattern
122			(?(R)... conditional test on whole pattern recursion
123			(?(Rn)... conditional test on recursion, by number
124			(?(R&name)... conditional test on recursion, by name
125	ph10	691	(*COMMIT) )
126			(*MARK) )
127			(*PRUNE) ) the backtracking control verbs
128			(*SKIP) )
129			(*THEN) )
130			</pre>
131			Support for some of these may be added in future.
132			</P>
133			<br><a name="SEC5" href="#TOC1">RETURN VALUES FROM JIT EXECUTION</a><br>
134			<P>
135			When a pattern is matched using JIT execution, the return values are the same
136			as those given by the interpretive <b>pcre_exec()</b> code, with the addition of
137			one new error code: PCRE_ERROR_JIT_STACKLIMIT. This means that the memory used
138			for the JIT stack was insufficient. See
139			<a href="#stackcontrol">"Controlling the JIT stack"</a>
140			below for a discussion of JIT stack usage. For compatibility with the
141			interpretive <b>pcre_exec()</b> code, no more than two-thirds of the
142			<i>ovector</i> argument is used for passing back captured substrings.
143			</P>
144			<P>
145			The error code PCRE_ERROR_MATCHLIMIT is returned by the JIT code if searching a
146			very large pattern tree goes on for too long, as it is in the same circumstance
147			when JIT is not used, but the details of exactly what is counted are not the
148			same. The PCRE_ERROR_RECURSIONLIMIT error code is never returned by JIT
149			execution.
150			</P>
151			<br><a name="SEC6" href="#TOC1">SAVING AND RESTORING COMPILED PATTERNS</a><br>
152			<P>
153			The code that is generated by the JIT compiler is architecture-specific, and is
154	ph10	708	also position dependent. For those reasons it cannot be saved (in a file or
155			database) and restored later like the bytecode and other data of a compiled
156			pattern. Saving and restoring compiled patterns is not something many people
157			do. More detail about this facility is given in the
158			<a href="pcreprecompile.html"><b>pcreprecompile</b></a>
159			documentation. It should be possible to run <b>pcre_study()</b> on a saved and
160			restored pattern, and thereby recreate the JIT data, but because JIT
161			compilation uses significant resources, it is probably not worth doing this;
162			you might as well recompile the original pattern.
163	ph10	691	<a name="stackcontrol"></a></P>
164			<br><a name="SEC7" href="#TOC1">CONTROLLING THE JIT STACK</a><br>
165			<P>
166			When the compiled JIT code runs, it needs a block of memory to use as a stack.
167			By default, it uses 32K on the machine stack. However, some large or
168			complicated patterns need more than this. The error PCRE_ERROR_JIT_STACKLIMIT
169			is given when there is not enough stack. Three functions are provided for
170	ph10	835	managing blocks of memory for use as JIT stacks.
171	ph10	691	</P>
172			<P>
173			The <b>pcre_jit_stack_alloc()</b> function creates a JIT stack. Its arguments
174			are a starting size and a maximum size, and it returns a pointer to an opaque
175			structure of type <b>pcre_jit_stack</b>, or NULL if there is an error. The
176			<b>pcre_jit_stack_free()</b> function can be used to free a stack that is no
177			longer needed. (For the technically minded: the address space is allocated by
178			mmap or VirtualAlloc.)
179			</P>
180			<P>
181			JIT uses far less memory for recursion than the interpretive code,
182			and a maximum stack size of 512K to 1M should be more than enough for any
183			pattern.
184			</P>
185			<P>
186			The <b>pcre_assign_jit_stack()</b> function specifies which stack JIT code
187			should use. Its arguments are as follows:
188			<pre>
189			pcre_extra *extra
190			pcre_jit_callback callback
191			void *data
192			</pre>
193			The <i>extra</i> argument must be the result of studying a pattern with
194			PCRE_STUDY_JIT_COMPILE. There are three cases for the values of the other two
195			options:
196			<pre>
197			(1) If <i>callback</i> is NULL and <i>data</i> is NULL, an internal 32K block
198			on the machine stack is used.
199
200			(2) If <i>callback</i> is NULL and <i>data</i> is not NULL, <i>data</i> must be
201			a valid JIT stack, the result of calling <b>pcre_jit_stack_alloc()</b>.
202
203			(3) If <i>callback</i> not NULL, it must point to a function that is called
204			with <i>data</i> as an argument at the start of matching, in order to
205			set up a JIT stack. If the result is NULL, the internal 32K stack
206			is used; otherwise the return value must be a valid JIT stack,
207			the result of calling <b>pcre_jit_stack_alloc()</b>.
208			</pre>
209			You may safely assign the same JIT stack to more than one pattern, as long as
210			they are all matched sequentially in the same thread. In a multithread
211			application, each thread must use its own JIT stack.
212			</P>
213			<P>
214			Strictly speaking, even more is allowed. You can assign the same stack to any
215			number of patterns as long as they are not used for matching by multiple
216			threads at the same time. For example, you can assign the same stack to all
217			compiled patterns, and use a global mutex in the callback to wait until the
218			stack is available for use. However, this is an inefficient solution, and
219			not recommended.
220			</P>
221			<P>
222			This is a suggestion for how a typical multithreaded program might operate:
223			<pre>
224			During thread initalization
225			thread_local_var = pcre_jit_stack_alloc(...)
226
227			During thread exit
228			pcre_jit_stack_free(thread_local_var)
229
230			Use a one-line callback function
231			return thread_local_var
232			</pre>
233			All the functions described in this section do nothing if JIT is not available,
234			and <b>pcre_assign_jit_stack()</b> does nothing unless the <b>extra</b> argument
235			is non-NULL and points to a <b>pcre_extra</b> block that is the result of a
236			successful study with PCRE_STUDY_JIT_COMPILE.
237			</P>
238	ph10	835	<br><a name="SEC8" href="#TOC1">EXAMPLE CODE</a><br>
239	ph10	691	<P>
240			This is a single-threaded example that specifies a JIT stack without using a
241			callback.
242			<pre>
243			int rc;
244			int ovector[30];
245			pcre *re;
246			pcre_extra *extra;
247			pcre_jit_stack *jit_stack;
248
249			re = pcre_compile(pattern, 0, &error, &erroffset, NULL);
250			/* Check for errors */
251			extra = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &error);
252			jit_stack = pcre_jit_stack_alloc(321024, 5121024);
253			/* Check for error (NULL) */
254			pcre_assign_jit_stack(extra, NULL, jit_stack);
255			rc = pcre_exec(re, extra, subject, length, 0, 0, ovector, 30);
256			/* Check results */
257			pcre_free(re);
258			pcre_free_study(extra);
259			pcre_jit_stack_free(jit_stack);
260
261			</PRE>
262			</P>
263	ph10	835	<br><a name="SEC9" href="#TOC1">SEE ALSO</a><br>
264	ph10	691	<P>
265			<b>pcreapi</b>(3)
266			</P>
267	ph10	835	<br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
268	ph10	691	<P>
269	ph10	835	Philip Hazel
270	ph10	691	<br>
271			University Computing Service
272			<br>
273			Cambridge CB2 3QH, England.
274			<br>
275			</P>
276	ph10	835	<br><a name="SEC11" href="#TOC1">REVISION</a><br>
277	ph10	691	<P>
278	ph10	835	Last updated: 19 October 2011
279	ph10	691	<br>
280			Copyright © 1997-2011 University of Cambridge.
281			<br>
282	ph10	678	<p>
283			Return to the <a href="index.html">PCRE index page</a>.
284			</p>