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Cope with platforms whose vsnprintf violates both POSIX and C99

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Bug: https://bugs.freedesktop.org/show_bug.cgi?id=11668
Reviewed-by: Will Thompson <will.thompson@collabora.co.uk>
This commit is contained in:
Simon McVittie 2011-06-21 14:09:32 +01:00
parent 029ecdf402
commit 7fc9c02666
1 changed files with 49 additions and 3 deletions
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52
dbus/dbus-sysdeps-unix.c
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@ -3021,14 +3021,60 @@ _dbus_full_duplex_pipe (int *fd1,
*
* @param format a printf-style format string
* @param args arguments for the format string
* @returns length of the given format string and args
* @returns length of the given format string and args, or -1 if no memory
*/
int
_dbus_printf_string_upper_bound (const char *format,
va_list args)
{
char c;
return vsnprintf (&c, 1, format, args);
char static_buf[1024];
int bufsize = sizeof (static_buf);
int len;
len = vsnprintf (static_buf, bufsize, format, args);
/* If vsnprintf() returned non-negative, then either the string fits in
* static_buf, or this OS has the POSIX and C99 behaviour where vsnprintf
* returns the number of characters that were needed, or this OS returns the
* truncated length.
*
* We ignore the possibility that snprintf might just ignore the length and
* overrun the buffer (64-bit Solaris 7), because that's pathological.
* If your libc is really that bad, come back when you have a better one. */
if (len == bufsize)
{
/* This could be the truncated length (Tru64 and IRIX have this bug),
* or the real length could be coincidentally the same. Which is it?
* If vsnprintf returns the truncated length, we'll go to the slow
* path. */
if (vsnprintf (static_buf, 1, format, args) == 1)
len = -1;
}
/* If vsnprintf() returned negative, we have to do more work.
* HP-UX returns negative. */
while (len < 0)
{
char *buf;
bufsize *= 2;
buf = dbus_malloc (bufsize);
if (buf == NULL)
return -1;
len = vsnprintf (buf, bufsize, format, args);
dbus_free (buf);
/* If the reported length is exactly the buffer size, round up to the
* next size, in case vsnprintf has been returning the truncated
* length */
if (len == bufsize)
len = -1;
}
return len;
}
/**