On Mon, Dec 12, 2011 at 10:30:27AM +0100, Andreas Schwab wrote:
> Jeff King <peff@xxxxxxxx> writes:
>
> > if (maxsize > 0) {
> > - ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
> > + va_copy(cp, ap);
> > + ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
>
> You also need to call va_end on the copy.
Silly me. Thanks for catching.
Junio, here's a corrected version.
-- >8 --
Subject: [PATCH] compat/snprintf: don't look at va_list twice
If you define SNPRINTF_RETURNS_BOGUS, we use a special
git_vsnprintf wrapper assumes that vsnprintf returns "-1"
instead of the number of characters that you would need to
store the result.
To do this, it invokes vsnprintf multiple times, growing a
heap buffer until we have enough space to hold the result.
However, this means we evaluate the va_list parameter
multiple times, which is generally a bad thing (it may be
modified by calls to vsnprintf, yielding undefined
behavior).
Instead, we must va_copy it and hand the copy to vsnprintf,
so we always have a pristine va_list.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
compat/snprintf.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/compat/snprintf.c b/compat/snprintf.c
index e1e0e75..42ea1ac 100644
--- a/compat/snprintf.c
+++ b/compat/snprintf.c
@@ -19,11 +19,14 @@
#undef vsnprintf
int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
{
+ va_list cp;
char *s;
int ret = -1;
if (maxsize > 0) {
- ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
+ va_copy(cp, ap);
+ ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
+ va_end(cp);
if (ret == maxsize-1)
ret = -1;
/* Windows does not NUL-terminate if result fills buffer */
@@ -42,7 +45,9 @@ int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
if (! str)
break;
s = str;
- ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
+ va_copy(cp, ap);
+ ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
+ va_end(cp);
if (ret == maxsize-1)
ret = -1;
}
--
1.7.8.13.g74677
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