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gnulib: %n is not supported on old glibc or on native win32

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On old glibc even if %n is supported we may get a crash, so it is
better to skip it while on native win32 %n will abort the program.
These changes were took from upstream.

https://bugzilla.gnome.org/show_bug.cgi?id=756382
This commit is contained in:
Ignacio Casal Quinteiro 2015-10-12 09:20:36 +02:00
parent 1533d9b60e
commit 94688bc12c
1 changed files with 27 additions and 0 deletions
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27
glib/gnulib/vasnprintf.c
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@ -699,9 +699,36 @@ vasnprintf (char *resultbuf, size_t *lengthp, const char *format, va_list args)
}
*p = dp->conversion;
#if HAVE_SNPRINTF
# if !(((__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) && !defined __UCLIBC__) || ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__))
p[1] = '%';
p[2] = 'n';
p[3] = '\0';
# else
/* On glibc2 systems from glibc >= 2.3 - probably also older
* ones - we know that snprintf's returns value conforms to
* ISO C 99: the gl_SNPRINTF_DIRECTIVE_N test passes.
* Therefore we can avoid using %n in this situation.
* On glibc2 systems from 2004-10-18 or newer, the use of %n
* in format strings in writable memory may crash the program
* (if compiled with _FORTIFY_SOURCE=2), so we should avoid it
* in this situation. */
/* On native Win32 systems (such as mingw), we can avoid using
* %n because:
* - Although the gl_SNPRINTF_TRUNCATION_C99 test fails,
* snprintf does not write more than the specified number
* of bytes. (snprintf (buf, 3, "%d %d", 4567, 89) writes
* '4', '5', '6' into buf, not '4', '5', '\0'.)
* - Although the gl_SNPRINTF_RETVAL_C99 test fails, snprintf
* allows us to recognize the case of an insufficient
* buffer size: it returns -1 in this case.
* On native Win32 systems (such as mingw) where the OS is
* Windows Vista, the use of %n in format strings by default
* crashes the program. See
* <http://gcc.gnu.org/ml/gcc/2007-06/msg00122.html> and
* <http://msdn2.microsoft.com/en-us/library/ms175782(VS.80).aspx>
* So we should avoid %n in this situation. */
p[1] = '\0';
# endif
#else
p[1] = '\0';
#endif