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Diffstat (limited to 'pcre/doc/html/pcrejit.html')
| -rw-r--r-- | pcre/doc/html/pcrejit.html | 57 |
1 files changed, 52 insertions, 5 deletions
diff --git a/pcre/doc/html/pcrejit.html b/pcre/doc/html/pcrejit.html index 210f1da0262..abb342522f9 100644 --- a/pcre/doc/html/pcrejit.html +++ b/pcre/doc/html/pcrejit.html @@ -79,9 +79,12 @@ API that is JIT-specific. </P> <P> If your program may sometimes be linked with versions of PCRE that are older -than 8.20, but you want to use JIT when it is available, you can test -the values of PCRE_MAJOR and PCRE_MINOR, or the existence of a JIT macro such -as PCRE_CONFIG_JIT, for compile-time control of your code. +than 8.20, but you want to use JIT when it is available, you can test the +values of PCRE_MAJOR and PCRE_MINOR, or the existence of a JIT macro such as +PCRE_CONFIG_JIT, for compile-time control of your code. Also beware that the +<b>pcre_jit_exec()</b> function was not available at all before 8.32, +and may not be available at all if PCRE isn't compiled with +--enable-jit. See the "JIT FAST PATH API" section below for details. </P> <br><a name="SEC4" href="#TOC1">SIMPLE USE OF JIT</a><br> <P> @@ -119,6 +122,20 @@ when you call <b>pcre_study()</b>: PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE </pre> +If using <b>pcre_jit_exec()</b> and supporting a pre-8.32 version of +PCRE, you can insert: +<pre> + #if PCRE_MAJOR >= 8 && PCRE_MINOR >= 32 + pcre_jit_exec(...); + #else + pcre_exec(...) + #endif +</pre> +but as described in the "JIT FAST PATH API" section below this assumes +version 8.32 and later are compiled with --enable-jit, which may +break. +<br> +<br> The JIT compiler generates different optimized code for each of the three modes (normal, soft partial, hard partial). When <b>pcre_exec()</b> is called, the appropriate code is run if it is available. Otherwise, the pattern is @@ -428,6 +445,36 @@ fast path, and if invalid data is passed, the result is undefined. Bypassing the sanity checks and the <b>pcre_exec()</b> wrapping can give speedups of more than 10%. </P> +<P> +Note that the <b>pcre_jit_exec()</b> function is not available in versions of +PCRE before 8.32 (released in November 2012). If you need to support versions +that old you must either use the slower <b>pcre_exec()</b>, or switch between +the two codepaths by checking the values of PCRE_MAJOR and PCRE_MINOR. +</P> +<P> +Due to an unfortunate implementation oversight, even in versions 8.32 +and later there will be no <b>pcre_jit_exec()</b> stub function defined +when PCRE is compiled with --disable-jit, which is the default, and +there's no way to detect whether PCRE was compiled with --enable-jit +via a macro. +</P> +<P> +If you need to support versions older than 8.32, or versions that may +not build with --enable-jit, you must either use the slower +<b>pcre_exec()</b>, or switch between the two codepaths by checking the +values of PCRE_MAJOR and PCRE_MINOR. +</P> +<P> +Switching between the two by checking the version assumes that all the +versions being targeted are built with --enable-jit. To also support +builds that may use --disable-jit either <b>pcre_exec()</b> must be +used, or a compile-time check for JIT via <b>pcre_config()</b> (which +assumes the runtime environment will be the same), or as the Git +project decided to do, simply assume that <b>pcre_jit_exec()</b> is +present in 8.32 or later unless a compile-time flag is provided, see +the "grep: un-break building with PCRE >= 8.32 without --enable-jit" +commit in git.git for an example of that. +</P> <br><a name="SEC12" href="#TOC1">SEE ALSO</a><br> <P> <b>pcreapi</b>(3) @@ -443,9 +490,9 @@ Cambridge CB2 3QH, England. </P> <br><a name="SEC14" href="#TOC1">REVISION</a><br> <P> -Last updated: 17 March 2013 +Last updated: 05 July 2017 <br> -Copyright © 1997-2013 University of Cambridge. +Copyright © 1997-2017 University of Cambridge. <br> <p> Return to the <a href="index.html">PCRE index page</a>. |