Use C99's va_copy to avoid undefined behavior on x86-64 GNU/Linux.

2 files changed, 7 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9fac265ae48..a1aa19e6f2e 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,8 @@
 2011-05-04  Paul Eggert  <eggert@cs.ucla.edu>
 
+        Use C99's va_copy to avoid undefined behavior on x86-64 GNU/Linux.
+        * eval.c (verror): doprnt a copy of ap, not the original.  (Bug#8545)
+
         * eval.c (verror): OK to create a string of up to MOST_POSITIVE_FIXNUM
         bytes.
 
diff --git a/src/eval.c b/src/eval.c
index 90ef02ef37b..6b4182cb319 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2002,7 +2002,10 @@ verror (const char *m, va_list ap)
 
   while (1)
     {
-      used = doprnt (buffer, size, m, m + mlen, ap);
+      va_list ap_copy;
+      va_copy (ap_copy, ap);
+      used = doprnt (buffer, size, m, m + mlen, ap_copy);
+      va_end (ap_copy);
 
       /* Note: the -1 below is because `doprnt' returns the number of bytes
          excluding the terminating null byte, and it always terminates with a