Comments about no_arg in the C++ wrapper.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@390 2f5784b3-3f2a-0410-8824-cb99058d5e15

3 files changed, 17 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 9832dd2..b02b213 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -56,6 +56,9 @@ Version 7.9 xx-xxx-09
 14. Added the non-standard REG_NOTEMPTY option to the POSIX interface.
 
 15. Added the PCRE_NO_START_OPTIMIZE match-time option.
+
+16. Added comments and documentation about mis-use of no_arg in the C++ 
+    wrapper.
       
 
 Version 7.8 05-Sep-08
diff --git a/doc/pcrecpp.3 b/doc/pcrecpp.3
index e52bd29..479e318 100644
--- a/doc/pcrecpp.3
+++ b/doc/pcrecpp.3
@@ -95,6 +95,11 @@ The matching interface supports at most 16 arguments per call.
 If you need more, consider using the more general interface
 \fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
 \fBDoMatch\fP.
+.P
+NOTE: Do not use \fBno_arg\fP, which is used internally to mark the end of a 
+list of optional arguments, as a placeholder for missing arguments, as this can 
+lead to segfaults.
+.
 .
 .SH "QUOTING METACHARACTERS"
 .rs
@@ -338,5 +343,5 @@ Copyright (c) 2007 Google Inc.
 .rs
 .sp
 .nf
-Last updated: 12 November 2007
+Last updated: 17 March 2009
 .fi
diff --git a/pcrecpp.h b/pcrecpp.h
index a87a816..7e79703 100644
--- a/pcrecpp.h
+++ b/pcrecpp.h
@@ -646,9 +646,15 @@ class PCRECPP_EXP_DEFN RE {
   // regexp wasn't valid on construction.
   int NumberOfCapturingGroups() const;
 
-  // The default value for an argument, to indicate no arg was passed in
+  // The default value for an argument, to indicate the end of the argument 
+  // list. This must be used only in optional argument defaults. It should NOT
+  // be passed explicitly. Some people have tried to use it like this:
+  //
+  //   FullMatch(x, y, &z, no_arg, &w);
+  //
+  // This is a mistake, and will not work.
   static Arg no_arg;
-
+  
  private:
 
   void Init(const string& pattern, const RE_Options* options);