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--- 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
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