Final file tidies for 8.41 release.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@1706 2f5784b3-3f2a-0410-8824-cb99058d5e15

1 files changed, 38 insertions, 3 deletions

diff --git a/doc/pcre.txt b/doc/pcre.txt
index 3614724..c027538 100644
--- a/doc/pcre.txt
+++ b/doc/pcre.txt
@@ -8366,8 +8366,10 @@ AVAILABILITY OF JIT SUPPORT
        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.
-       Also  beware that the pcre_jit_exec() function was not available before
-       8.32. See "JIT FAST PATH API" section below for details.
+       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
@@ -8409,6 +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
@@ -8704,6 +8718,27 @@ JIT FAST PATH API
        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
 
@@ -8719,7 +8754,7 @@ AUTHOR
 
 REVISION
 
-       Last updated: 13 June 2017
+       Last updated: 05 July 2017
        Copyright (c) 1997-2017 University of Cambridge.
 ------------------------------------------------------------------------------