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Diffstat (limited to 'pcre/doc/pcre.txt')
| -rw-r--r-- | pcre/doc/pcre.txt | 49 |
1 files changed, 46 insertions, 3 deletions
diff --git a/pcre/doc/pcre.txt b/pcre/doc/pcre.txt index d68d5033ceb..c027538f500 100644 --- a/pcre/doc/pcre.txt +++ b/pcre/doc/pcre.txt @@ -8365,7 +8365,11 @@ AVAILABILITY OF JIT SUPPORT 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. + macro such as PCRE_CONFIG_JIT, for compile-time control of your code. + Also beware that the pcre_jit_exec() 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. SIMPLE USE OF JIT @@ -8407,6 +8411,18 @@ SIMPLE USE OF JIT PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE + If using pcre_jit_exec() and supporting a pre-8.32 version of PCRE, you + can insert: + + #if PCRE_MAJOR >= 8 && PCRE_MINOR >= 32 + pcre_jit_exec(...); + #else + pcre_exec(...) + #endif + + 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. + The JIT compiler generates different optimized code for each of the three modes (normal, soft partial, hard partial). When pcre_exec() is called, the appropriate code is run if it is available. Otherwise, the @@ -8696,6 +8712,33 @@ JIT FAST PATH API Bypassing the sanity checks and the pcre_exec() wrapping can give speedups of more than 10%. + Note that the pcre_jit_exec() 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 pcre_exec(), or switch + between the two codepaths by checking the values of PCRE_MAJOR and + PCRE_MINOR. + + Due to an unfortunate implementation oversight, even in versions 8.32 + and later there will be no pcre_jit_exec() 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. + + 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 + pcre_exec(), or switch between the two codepaths by checking the values + of PCRE_MAJOR and PCRE_MINOR. + + 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 pcre_exec() must be used, or a + compile-time check for JIT via pcre_config() (which assumes the runtime + environment will be the same), or as the Git project decided to do, + simply assume that pcre_jit_exec() 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. + SEE ALSO @@ -8711,8 +8754,8 @@ AUTHOR REVISION - Last updated: 17 March 2013 - Copyright (c) 1997-2013 University of Cambridge. + Last updated: 05 July 2017 + Copyright (c) 1997-2017 University of Cambridge. ------------------------------------------------------------------------------ |