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@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Dec 12, 2011 at 09:25 UTC
a9bfbc5b698103b1553e1023c4f77001cc861e79
1 file changed
+7
-2
compat/snprintf.c
+7
-2
@@ -19,11 +19,14 @@
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#undef vsnprintf
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int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
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{
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+ va_list cp;
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char *s;
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int ret = -1;
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if (maxsize > 0) {
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- ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
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+ va_copy(cp, ap);
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+ ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
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+ va_end(cp);
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if (ret == maxsize-1)
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ret = -1;
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/* 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)
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if (! str)
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break;
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s = str;
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- ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
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+ va_copy(cp, ap);
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+ ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
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+ va_end(cp);
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if (ret == maxsize-1)
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ret = -1;
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}