Don't use %n on native Woe32 systems, to avoid a crash on Windows Vista systems.

diff --git a/ChangeLog b/ChangeLog
index 649d127..aa534f6 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2008-02-07  Bruno Haible  <bruno@clisp.org>
+
+       * lib/vasnprintf.c (VASNPRINTF): Don't use %n on native Woe32 systems.
+       Avoids a crash on Windows Vista.
+       Reported by Simon Josefsson <simon@josefsson.org>.
+
 2008-02-06  Bruno Haible  <bruno@clisp.org>
 
        Fix *printf behaviour regarding the left-adjust flag on HP-UX 10.20.

diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c
index 8377d31..968835a 100644 (file)
--- a/lib/vasnprintf.c
+++ b/lib/vasnprintf.c
@@ -4010,7 +4010,7 @@ VASNPRINTF (DCHAR_T *resultbuf, size_t *lengthp,
 #endif
                  *fbp = dp->conversion;
 #if USE_SNPRINTF
-# if !(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3))
+# if !(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3) || ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__))
                fbp[1] = '%';
                fbp[2] = 'n';
                fbp[3] = '\0';
@@ -4023,6 +4023,21 @@ VASNPRINTF (DCHAR_T *resultbuf, size_t *lengthp,
                   in format strings in writable memory may crash the program
                   (if compiled with _FORTIFY_SOURCE=2), so we should avoid it
                   in this situation.  */
+               /* On native Win32 systems (such as mingw), we can avoid using
+                  %n because:
+                    - Although the gl_SNPRINTF_TRUNCATION_C99 test fails,
+                      snprintf does not write more than the specified number
+                      of bytes. (snprintf (buf, 3, "%d %d", 4567, 89) writes
+                      '4', '5', '6' into buf, not '4', '5', '\0'.)
+                    - Although the gl_SNPRINTF_RETVAL_C99 test fails, snprintf
+                      allows us to recognize the case of an insufficient
+                      buffer size: it returns -1 in this case.
+                  On native Win32 systems (such as mingw) where the OS is
+                  Windows Vista, the use of %n in format strings by default
+                  crashes the program. See
+                    <http://gcc.gnu.org/ml/gcc/2007-06/msg00122.html> and
+                    <http://msdn2.microsoft.com/en-us/library/ms175782(VS.80).aspx>
+                  So we should avoid %n in this situation.  */
                fbp[1] = '\0';
 # endif
 #else