[PATCH v2] [DEBUG] Use va_copy when reusing a va_list

[Jonathan Nieder <jrnieder@gmail.com>]

When tracing (with the DEBUG compile-time option set to 1 or 2),
exverror calls TRACEV to print its arguments before passing them on.
So the arguments are consumed by the time exvwarning looks for them,
resulting in a segfault:

 $ sh -c '"'
 sh: Syntax error: Unterminated quoted string
 $ sh -o debug -c '"'
 sh: Segmentation fault (core dumped)

Make a copy with va_copy to avoid this.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
v1 left out va_end.  Sorry for the nonsense.

 src/error.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/error.c b/src/error.c
index f1a358d..db2eb62 100644
--- a/src/error.c
+++ b/src/error.c
@@ -143,8 +143,11 @@ exverror(int cond, const char *msg, va_list ap)
 {
 #ifdef DEBUG
 	if (msg) {
+		va_list aq;
 		TRACE(("exverror(%d, \"", cond));
-		TRACEV((msg, ap));
+		va_copy(aq, ap);
+		TRACEV((msg, aq));
+		va_end(aq);
 		TRACE(("\") pid=%d\n", getpid()));
 	} else
 		TRACE(("exverror(%d, NULL) pid=%d\n", cond, getpid()));
-- 
1.7.4.1