2 files changed, 34 insertions, 17 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 0993b67cbca..68f3dbdedcb 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2011-04-08  Paul Eggert  <eggert@cs.ucla.edu>
+
+        * eval.c: Port to Windows vsnprintf (Bug#8435).
+        Include <limits.h>.
+        (SIZE_MAX): Define if the headers do not.
+        (verror): Do not give up if vsnprintf returns a negative count.
+        Instead, grow the buffer.  This ports to Windows vsnprintf, which
+        does not conform to C99.  Problem reported by Eli Zaretskii.
+        Also, simplify the allocation scheme, by avoiding the need for
+        calling realloc, and removing the ALLOCATED variable.
+
 2011-04-07  Paul Eggert  <eggert@cs.ucla.edu>
 
         * eval.c (verror): Initial buffer size is 4000 (not 200) bytes.
diff --git a/src/eval.c b/src/eval.c
index f794a18da7d..0f9e012b823 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -18,6 +18,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #include <config.h>
+#include <limits.h>
 #include <setjmp.h>
 #include "lisp.h"
 #include "blockinput.h"
@@ -30,6 +31,10 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "xterm.h"
 #endif
 
+#ifndef SIZE_MAX
+# define SIZE_MAX ((size_t) -1)
+#endif
+
 /* This definition is duplicated in alloc.c and keyboard.c.  */
 /* Putting it in lisp.h makes cc bomb out!  */
 
@@ -1978,36 +1983,37 @@ verror (const char *m, va_list ap)
 {
   char buf[4000];
   size_t size = sizeof buf;
-  size_t size_max = (size_t) -1;
+  size_t size_max =
+    min (MOST_POSITIVE_FIXNUM, min (INT_MAX, SIZE_MAX - 1)) + 1;
   char *buffer = buf;
-  int allocated = 0;
   int used;
   Lisp_Object string;
 
   while (1)
     {
       used = vsnprintf (buffer, size, m, ap);
+
       if (used < 0)
-        used = 0;
-      if (used < size)
-        break;
-      if (size <= size_max / 2)
-        size *= 2;
-      else if (size < size_max)
-        size = size_max;
-      else
-        memory_full ();
-      if (allocated)
-        buffer = (char *) xrealloc (buffer, size);
-      else
         {
-          buffer = (char *) xmalloc (size);
-          allocated = 1;
+          /* Non-C99 vsnprintf, such as w32, returns -1 when SIZE is too small.
+             Guess a larger USED to work around the incompatibility.  */
+          used = (size <= size_max / 2 ? 2 * size
+                  : size < size_max ? size_max - 1
+                  : size_max);
         }
+      else if (used < size)
+        break;
+      if (size_max <= used)
+        memory_full ();
+      size = used + 1;
+
+      if (buffer != buf)
+        xfree (buffer);
+      buffer = (char *) xmalloc (size);
     }
 
   string = make_string (buffer, used);
-  if (allocated)
+  if (buffer != buf)
     xfree (buffer);
 
   xsignal1 (Qerror, string);