--- m4-1.4.10/lib/vasnprintf.c_old	2007-07-05 13:48:27.000000000 +0200
+++ m4-1.4.10/lib/vasnprintf.c	2007-12-13 13:38:39.000000000 +0100
@@ -3385,10 +3385,22 @@
 #endif
 		  *fbp = dp->conversion;
 #if USE_SNPRINTF
+#if !(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3))
 		fbp[1] = '%';
 		fbp[2] = 'n';
 		fbp[3] = '\0';
 #else
+		/* On glibc2 systems from glibc >= 2.3 - probably also older
+		ones - we know that snprintf's returns value conforms to
+		ISO C 99: the gl_SNPRINTF_DIRECTIVE_N test passes.
+		Therefore we can avoid using %n in this situation.
+		On glibc2 systems from 2004-10-18 or newer, the use of %n
+		in format strings in writable memory may crash the program
+		(if compiled with _FORTIFY_SOURCE=2), so we should avoid it
+		in this situation.  */
+		fbp[1] = '\0';
+#endif 
+#else
 		fbp[1] = '\0';
 #endif