Fix bug in emulated memmove() for downward moves.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@118 2f5784b3-3f2a-0410-8824-cb99058d5e15

2 files changed, 24 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index 45e4fa8..9841c87 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -60,9 +60,16 @@ Version 7.1 05-Mar-07
     called when UTF-8 support is disabled. Otherwise there are problems with a
     shared library.
 
-10. The emulated memmove() function in pcre_internal.h (provided for those
-    environments that have neither memmove() nor bcopy()) was defining its
-    arguments as char * instead of void *.
+10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
+
+    (a) It was defining its arguments as char * instead of void *.
+     
+    (b) It was assuming that all moves were upwards in memory; this was true 
+        a long time ago when I wrote it, but is no longer the case. 
+
+    The emulated memove() is provided for those environments that have neither
+    memmove() nor bcopy(). I didn't think anyone used it these days, but that 
+    is clearly not the case, as these two bugs were recently reported.
     
 11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
     and Detrail to create the HTML documentation, the .txt form of the man 
@@ -105,7 +112,7 @@ Version 7.1 05-Mar-07
         I have added a new /Z option to pcretest that replaces the length and 
         offset values with spaces. This is now used to make test 3 independent 
         of link size.
-
+        
 
 Version 7.0 19-Dec-06
 ---------------------
diff --git a/pcre_internal.h b/pcre_internal.h
index d0956af..9caec72 100644
--- a/pcre_internal.h
+++ b/pcre_internal.h
@@ -200,9 +200,7 @@ option on the command line. */
 /* To cope with SunOS4 and other systems that lack memmove() but have bcopy(),
 define a macro for memmove() if HAVE_MEMMOVE is false, provided that HAVE_BCOPY
 is set. Otherwise, include an emulating function for those systems that have
-neither (there some non-Unix environments where this is the case). This assumes
-that all calls to memmove are moving strings upwards in store, which is the
-case in PCRE. */
+neither (there some non-Unix environments where this is the case). */
 
 #if ! HAVE_MEMMOVE
 #undef  memmove        /* some systems may have a macro */
@@ -215,10 +213,18 @@ pcre_memmove(void *d, const void *s, size_t n)
 size_t i;
 unsigned char *dest = (unsigned char *)d;
 const unsigned char *src = (const unsigned char *)s;
-dest += n;
-src += n;
-for (i = 0; i < n; ++i) *(--dest) = *(--src);
-return (void *)dest;
+if (dest > src)
+  {
+  dest += n;
+  src += n;
+  for (i = 0; i < n; ++i) *(--dest) = *(--src);
+  return (void *)dest;
+  }
+else
+  {
+  for (i = 0; i < n; ++i) *dest++ = *src++;
+  return (void *)(dest - n); 
+  }    
 }
 #define memmove(a, b, c) pcre_memmove(a, b, c)
 #endif   /* not HAVE_BCOPY */