cpython/Python/mysnprintf.c

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#include "Python.h"
/* snprintf() and vsnprintf() wrappers.
If the platform has vsnprintf, we use it, else we
emulate it in a half-hearted way. Even if the platform has it, we wrap
it because platforms differ in what vsnprintf does in case the buffer
is too small: C99 behavior is to return the number of characters that
would have been written had the buffer not been too small, and to set
the last byte of the buffer to \0. At least MS _vsnprintf returns a
negative value instead, and fills the entire buffer with non-\0 data.
The wrappers ensure that str[size-1] is always \0 upon return.
PyOS_snprintf and PyOS_vsnprintf never write more than size bytes
(including the trailing '\0') into str.
Return value (rv):
When 0 <= rv < size, the output conversion was unexceptional, and
rv characters were written to str (excluding a trailing \0 byte at
str[rv]).
When rv >= size, output conversion was truncated, and a buffer of
size rv+1 would have been needed to avoid truncation. str[size-1]
is \0 in this case.
When rv < 0, "something bad happened". str[size-1] is \0 in this
case too, but the rest of str is unreliable. It could be that
an error in format codes was detected by libc, or on platforms
with a non-C99 vsnprintf simply that the buffer wasn't big enough
to avoid truncation, or on platforms without any vsnprintf that
PyMem_Malloc couldn't obtain space for a temp buffer.
CAUTION: Unlike C99, str != NULL and size > 0 are required.
Also, size must be smaller than INT_MAX.
*/
int
PyOS_snprintf(char *str, size_t size, const char *format, ...)
{
int rc;
va_list va;
va_start(va, format);
rc = PyOS_vsnprintf(str, size, format, va);
va_end(va);
return rc;
}
int
PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)
{
assert(str != NULL);
assert(size > 0);
assert(size <= (INT_MAX - 1));
assert(format != NULL);
int len; /* # bytes written, excluding \0 */
/* We take a size_t as input but return an int. Sanity check
* our input so that it won't cause an overflow in the
* vsnprintf return value. */
if (size > INT_MAX - 1) {
len = -666;
goto Done;
}
#if defined(_MSC_VER)
len = _vsnprintf(str, size, format, va);
#else
len = vsnprintf(str, size, format, va);
#endif
Merged revisions 63562,63570,63728,63734,63784,63788,63802,63817,63827,63839,63887,63975,63998 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r63562 | martin.v.loewis | 2008-05-23 17:06:50 +0200 (Fri, 23 May 2008) | 2 lines Patch #1722225: Support QNX 6. ........ r63570 | trent.nelson | 2008-05-23 22:33:14 +0200 (Fri, 23 May 2008) | 1 line Introduce a user macro named $(externalsDir), which should point to the root directory of where all the external sources should live. Developers can change this value if their external sources live elsewhere. The default of '..\..' matches the current status quo. ........ r63728 | gregory.p.smith | 2008-05-26 23:16:34 +0200 (Mon, 26 May 2008) | 4 lines Fix issue2589: there was a potential integer overflow leading to memory corruption on esoteric platforms and incorrect behavior on normal platforms. ........ r63734 | gregory.p.smith | 2008-05-27 00:07:28 +0200 (Tue, 27 May 2008) | 3 lines Fix issue2588: Do not execute str[size-1] = '\0' when a 0 size is passed in. (The assert won't prevent this in non-debug builds). ........ r63784 | raymond.hettinger | 2008-05-29 10:38:23 +0200 (Thu, 29 May 2008) | 1 line Fix two typos. ........ r63788 | facundo.batista | 2008-05-29 18:39:26 +0200 (Thu, 29 May 2008) | 6 lines Fixed the semantic of timeout for socket.create_connection and all the upper level libraries that use it, including urllib2. Added and fixed some tests, and changed docs correspondingly. Thanks to John J Lee for the patch and the pusing, :) ........ r63802 | mark.dickinson | 2008-05-30 04:46:53 +0200 (Fri, 30 May 2008) | 2 lines Fix typo in testSum ........ r63817 | raymond.hettinger | 2008-05-30 20:20:50 +0200 (Fri, 30 May 2008) | 8 lines * Mark intermedidate computes values (hi, lo, yr) as volatile. * Expand comments. * Swap variable names in the sum_exact code so that x and y are consistently chosen as the larger and smaller magnitude values respectively. ........ r63827 | raymond.hettinger | 2008-05-31 05:24:31 +0200 (Sat, 31 May 2008) | 1 line Implement heapq in terms of less-than (to match list.sort()). ........ r63839 | gerhard.haering | 2008-05-31 23:33:27 +0200 (Sat, 31 May 2008) | 2 lines Fixed rowcount for SELECT statements. They're -1 now (again), for better DB-API 2.0 compliance. ........ r63887 | gregory.p.smith | 2008-06-02 06:05:52 +0200 (Mon, 02 Jun 2008) | 4 lines Fix issue 2782: be less strict about the format string type in strftime. Accept unicode and anything else ParseTuple "s#" can deal with. This matches the time.strftime behavior. ........ r63975 | neal.norwitz | 2008-06-06 06:47:01 +0200 (Fri, 06 Jun 2008) | 3 lines Aldo Cortesi confirmed this is still needed for OpenBSD 4.2 and 4.3. (I didn't regen configure, since I don't have a working autoconf.) ........ r63998 | raymond.hettinger | 2008-06-06 23:47:51 +0200 (Fri, 06 Jun 2008) | 1 line Issue 3501: Make heapq support both __le__ and __lt__. ........
2008-06-10 17:40:04 +00:00
Done:
if (size > 0) {
str[size-1] = '\0';
}
return len;
}