[FFmpeg-cvslog] compat/vsnprintf: return number of bytes required on truncation.

[Ronald S. Bultje]

ffmpeg | branch: master | Ronald S. Bultje <rsbultje at gmail.com> | Fri Sep 14 18:56:46 2012 +0000| [c1c8fdab46414e3518400d6ee18916d2444a06d7] | committer: Derek Buitenhuis

compat/vsnprintf: return number of bytes required on truncation.

This conforms to C99, but requires Windows >= XP.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c1c8fdab46414e3518400d6ee18916d2444a06d7
---

 compat/msvcrt/snprintf.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/compat/msvcrt/snprintf.c b/compat/msvcrt/snprintf.c
index 2cdec74..0af7b54 100644
--- a/compat/msvcrt/snprintf.c
+++ b/compat/msvcrt/snprintf.c
@@ -26,6 +26,10 @@
 
 #include "libavutil/error.h"
 
+#if !defined(va_copy) && defined(_MSC_VER)
+#define va_copy(dst, src) ((dst) = (src))
+#endif
+
 int avpriv_snprintf(char *s, size_t n, const char *fmt, ...)
 {
     va_list ap;
@@ -42,9 +46,10 @@ int avpriv_vsnprintf(char *s, size_t n, const char *fmt,
                      va_list ap)
 {
     int ret;
+    va_list ap_copy;
 
     if (n == 0)
-        return 0;
+        return _vscprintf(fmt, ap);
     else if (n > INT_MAX)
         return AVERROR(EOVERFLOW);
 
@@ -55,9 +60,11 @@ int avpriv_vsnprintf(char *s, size_t n, const char *fmt,
      * _snprintf/_vsnprintf() to workaround this problem.
      * See http://msdn.microsoft.com/en-us/library/1kt27hek(v=vs.80).aspx */
     memset(s, 0, n);
-    ret = _vsnprintf(s, n - 1, fmt, ap);
+    va_copy(ap_copy, ap);
+    ret = _vsnprintf(s, n - 1, fmt, ap_copy);
+    va_end(ap_copy);
     if (ret == -1)
-        ret = n;
+        ret = _vscprintf(fmt, ap);
 
     return ret;
 }