X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/1cc59d374be28e0f2a27720d003271216676c12e..6bf342e1eb87c656de34d668d7303a7d0138e89a:/src/src/pcre/pcre_version.c

diff --git a/src/src/pcre/pcre_version.c b/src/src/pcre/pcre_version.c
index 47f889f1d..1a30fe014 100644
--- a/src/src/pcre/pcre_version.c
+++ b/src/src/pcre/pcre_version.c
@@ -1,4 +1,4 @@
-/* $Cambridge: exim/src/src/pcre/pcre_version.c,v 1.3 2006/11/07 16:50:36 ph10 Exp $ */
+/* $Cambridge: exim/src/src/pcre/pcre_version.c,v 1.4 2007/01/23 15:08:45 ph10 Exp $ */
 
 /*************************************************
 *      Perl-Compatible Regular Expressions       *
@@ -51,16 +51,38 @@ string that identifies the PCRE version that is in use. */
 *          Return version string                 *
 *************************************************/
 
+/* These macros are the standard way of turning unquoted text into C strings.
+They allow macros like PCRE_MAJOR to be defined without quotes, which is
+convenient for user programs that want to test its value. */
+
 #define STRING(a)  # a
 #define XSTRING(s) STRING(s)
 
+/* A problem turned up with PCRE_PRERELEASE, which is defined empty for
+production releases. Originally, it was used naively in this code:
+
+  return XSTRING(PCRE_MAJOR)
+         "." XSTRING(PCRE_MINOR)
+             XSTRING(PCRE_PRERELEASE)
+         " " XSTRING(PCRE_DATE);
+
+However, when PCRE_PRERELEASE is empty, this leads to an attempted expansion of
+STRING(). The C standard states: "If (before argument substitution) any
+argument consists of no preprocessing tokens, the behavior is undefined." It
+turns out the gcc treats this case as a single empty string - which is what we
+really want - but Visual C grumbles about the lack of an argument for the
+macro. Unfortunately, both are within their rights. To cope with both ways of
+handling this, I had resort to some messy hackery that does a test at run time.
+I could find no way of detecting that a macro is defined as an empty string at
+pre-processor time. This hack uses a standard trick for avoiding calling
+the STRING macro with an empty argument when doing the test. */
+
 PCRE_DATA_SCOPE const char *
 pcre_version(void)
 {
-return XSTRING(PCRE_MAJOR)
-       "." XSTRING(PCRE_MINOR)
-           XSTRING(PCRE_PRERELEASE)
-       " " XSTRING(PCRE_DATE);
+return (XSTRING(Z PCRE_PRERELEASE)[1] == 0)?
+  XSTRING(PCRE_MAJOR.PCRE_MINOR PCRE_DATE) :
+  XSTRING(PCRE_MAJOR.PCRE_MINOR) XSTRING(PCRE_PRERELEASE PCRE_DATE);
 }
 
 /* End of pcre_version.c */