Re: [PATCH v3] gettext.c: detect the vsnprintf bug at runtime

> Bug 6530 [1] in glibc causes "git show v0.99.6~1" to fail with error
> "your vsnprintf is broken". The workaround avoids that, but it
> corrupts system error messages in non-C locales.
>
> The bug has been fixed since 2.17. We could know running glibc version
> with gnu_get_libc_version(). But version is not a sure way to detect
> the bug because downstream may back port the fix to older versions. Do
> a runtime test that immitates the call flow that leads to "your
> vsnprintf is broken". Only enable the workaround if the test fails.
>
> Tested on Gentoo Linux, glibc 2.16.0 and 2.17, amd64.
>
> [1] http://sourceware.org/bugzilla/show_bug.cgi?id=6530
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  v3 goes with runtime test instead of version check.
>
>  gettext.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/gettext.c b/gettext.c
> index 71e9545..eed7c7f 100644
> --- a/gettext.c
> +++ b/gettext.c
> @@ -29,6 +29,17 @@ int use_gettext_poison(void)
>  #endif
>  
>  #ifndef NO_GETTEXT
> +static int test_vsnprintf(const char *fmt, ...)
> +{
> +	char buf[26];
> +	int ret;
> +	va_list ap;
> +	va_start(ap, fmt);
> +	ret = vsnprintf(buf, sizeof(buf), fmt, ap);
> +	va_end(ap);
> +	return ret;
> +}
> +

> +	/* the string is taken from v0.99.6~1 */
> +	if (test_vsnprintf("%.*s", 13, "David_K\345gedal") < 0)
> +		setlocale(LC_CTYPE, "C");
>  }
>  
>  void git_setup_gettext(void)