patchgettext.c: only work around the vsnprintf bug on glibc < 2.17

> diff --git a/gettext.c b/gettext.c
> index 71e9545..91e679d 100644
> --- a/gettext.c
> +++ b/gettext.c
> @@ -18,6 +18,13 @@
>  #	endif
>  #endif
>  
> +#ifdef USE_GLIBC
> +#ifndef _GNU_SOURCE
> +#define _GNU_SOURCE
> +#endif

> On 2013-11-30 13.01, Nguyễn Thái Ngọc Duy wrote:
>> Bug 6530 [1] causes "git show v0.99.6~1" to fail with error "your
> causes or caused (as we have a work around?)
>> vsnprintf is broken". The workaround avoids that, but it corrupts
>> system error messages in non-C locales.
> [snip]
>> The bug in glibc has been fixed since 2.17. If git is built with glibc, it can
>                 ^^^^^^ (Should we name glibc ?)

> [snip]
>> -     setlocale(LC_MESSAGES, "");
>> -     init_gettext_charset("git");
>> +     setlocale(vsnprintf_broken ? LC_MESSAGES : LC_ALL, "");
> 1) One thing I don't understand: Why do we need to set LC_ALL ?
> The old patch didn't do it, or what do I miss ?
> See https://wiki.debian.org/Locale :
> Using LC_ALL is strongly discouraged as it overrides everything. Please use it only when testing and never set it in a startup file.

> 2) I stole the code partly from here:
>    http://sourceware.org/bugzilla/show_bug.cgi?id=6530
> ----------------------
> #include <stdio.h>
> #include <locale.h>
> #include <gnu/libc-version.h>
>
> #define STR "²éľÂíɱ²¡¶¾£¬ÖܺèµtÄúµÄ360²»×¨Òµ£¡"
>
> int main(void) {
>         char buf[200];
>         setlocale(LC_ALL, "");
>                                 printf("gnu_glibc_version()=%s\n",  gnu_get_libc_version());
>         printf("ret(snprintf)=%d\n", snprintf(buf, 150, "%.50s", STR));
>         return 0;
> }
>
> ----------------------
> Then I run it on different machines:
>
> gnu_glibc_version()=2.11.3 /* Ubuntu 10.4, no updates */
> gnu_glibc_version()=2.11.3 /* Debian Squeze  ?*/
> gnu_glibc_version()=2.13 /* Debian Wheezy */
> ret(snprintf)=50 /* All the 3 above */
> -------------
> So could it be that libc is patched in Debian/Ubuntu, and we
> can do a runtime check (rather than looking at the version number),
> similar to the code above ?

> ------------
>
> 3) The patch didn't break anything here (Debian, Mac OS).
>
> 4) Could it be good to have a test case ? Is t0204 good for inspiration ?
>
> 5) I can do more testing if needed.
>
> /Torsten
>
>
>

> 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)

>> --- 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;
>> +}
>> +
> this function alway run each time we run git commad while libc is
> static. It is waste.
>> +     /* 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)
>
> I suggest use C preprocessor instead. The person who complete git (make debian, rpm etc. package) decide  enable it or not (disable by default). Most of people use git from distribution instead of complete it from source.
>
> #ifndef VSNPRINTF_OK
>         setlocale(LC_CTYPE, "C");
> #endif
>

>> I suggest use C preprocessor instead. The person who complete git (make debian, rpm etc. package) decide  enable it or not (disable by default). Most of people use git from distribution instead of complete it from source.
>>
>> #ifndef VSNPRINTF_OK
>>         setlocale(LC_CTYPE, "C");
>> #endif
>>
> A single vsnprintf is cheap enough that I would not worry about
> performance impact. Given a choice between this and distro
> maintainers, some of them do check release notes, some not so much,
> I'd rather go with this.

> On 02/12/2013 12:57, Duy Nguyen wrote:
>>> I suggest use C preprocessor instead. The person who complete git (make debian, rpm etc. package) decide  enable it or not (disable by default). Most of people use git from distribution instead of complete it from source.
>>>
>>> #ifndef VSNPRINTF_OK
>>>         setlocale(LC_CTYPE, "C");
>>> #endif
>>>
>> A single vsnprintf is cheap enough that I would not worry about
>> performance impact. Given a choice between this and distro
>> maintainers, some of them do check release notes, some not so much,
>> I'd rather go with this.
> We can set this macro automatically  by using autoconf.
> Add following code in configure.ac
>
>
> AC_LANG_CONFTEST(
> [AC_LANG_PROGRAM([[
> #include <stdio.h>
> #include <locale.h>
> #include <gnu/libc-version.h>
>
> #define STR "David_K\345gedal"
> ]],[[
>     char buf[20];
>     setlocale(LC_ALL, "en_US.UTF-8");
>     if (snprintf(buf, 13, "%.13s", STR) < 0){
>         printf("0");
>     }else{
>         printf("1");
>     }
> ]])])
> gcc -o conftest conftest.c
> AC_DEFINE([VSNPRINTF_OK], [m4_esyscmd([./conftest])], [Enable l10n libc
> if vnsprintf OK])
>
> You can change c code here!
>

> On 02/12/2013 12:57, Duy Nguyen wrote:
>>> I suggest use C preprocessor instead. The person who complete git (make debian, rpm etc. package) decide  enable it or not (disable by default). Most of people use git from distribution instead of complete it from source.
>>>
>>> #ifndef VSNPRINTF_OK
>>>         setlocale(LC_CTYPE, "C");
>>> #endif
>>>
>> A single vsnprintf is cheap enough that I would not worry about
>> performance impact. Given a choice between this and distro
>> maintainers, some of them do check release notes, some not so much,
>> I'd rather go with this.
> We can set this macro automatically  by using autoconf.
> Add following code in configure.ac

>
>
> AC_LANG_CONFTEST(
> [AC_LANG_PROGRAM([[
> #include <stdio.h>
> #include <locale.h>
> #include <gnu/libc-version.h>
>
> #define STR "David_K\345gedal"
> ]],[[
>     char buf[20];
>     setlocale(LC_ALL, "en_US.UTF-8");
>     if (snprintf(buf, 13, "%.13s", STR) < 0){
>         printf("0");
>     }else{
>         printf("1");
>     }
> ]])])
> gcc -o conftest conftest.c
> AC_DEFINE([VSNPRINTF_OK], [m4_esyscmd([./conftest])], [Enable l10n libc
> if vnsprintf OK])
>
> You can change c code here!
>
> --
> Trần Ngọc Quân.
>