[PATCH] error, warn, warnx: Use __fxprintf for wide printing [BZ #23519]

[Florian Weimer]

On 08/14/2018 03:22 PM, Gabriel F. T. Gomes wrote:
> On Tue, 14 Aug 2018, Florian Weimer wrote:
> 
>> void
>> vwarnx (const char *format, __gnuc_va_list ap)
>> {
>>    flockfile (stderr);
>> -  if (_IO_fwide (stderr, 0) > 0)
>> -    {
>> -      __fwprintf (stderr, L"%s: ", __progname);
>> -      convert_and_print (format, ap);
>> -      putwc_unlocked (L'\n', stderr);
>> -    }
>> -  else
>> -    {
>> -      fprintf (stderr, "%s: ", __progname);
>> -      if (format)
>> -	vfprintf (stderr, format, ap);
>> -      putc_unlocked ('\n', stderr);
>> -    }
>> +  __fxprintf (stderr, "%s: ", __progname);
>> +  if (format)
>> +    __vfxprintf (stderr, format, ap);
>> +  __fxprintf (stderr, "\n");
> 
> Is it true that you can remove the call to 'convert_and_print' because
> __fxprintf and __vfxprintf already check the wideness of the output and
> convert (indirectly via locked_vfxprintf)?

Correct.  I failed to convert an fputs_unlocked call.

I'm also adding a test in the attached patch.

>> --- a/misc/error.c
>> +++ b/misc/error.c
>> @@ -203,72 +203,14 @@ static void _GL_ATTRIBUTE_FORMAT_PRINTF (3, 0) _GL_ARG_NONNULL ((3))
>> error_tail (int status, int errnum, const char *message, va_list args)
>> {
>> #if _LIBC
>> +  int ret = __vfxprintf (stderr, message, args);
>> +  if (ret < 0 && errno == ENOMEM && _IO_fwide (stderr, 0) > 0)
>> +    /* Leave a trace in case the heap allocation of the message string
>> +       failed.  */
>> +    fputws_unlocked (L"out of memory\n", stderr);
>> +#else
>> +  vfprintf (stderr, message, args);
>> #endif
> 
> Just out of curiosity, how do we know that other programs use this code
> outside of glibc?  (assuming this is the reason for the _LIBC check).

In these cases, it is useful to check gnulib.  Often, there is a copy of 
the code there as well, and there is an expectation that we keep merging 
from gnulib (but this is not always possible).

Thanks,
Florian
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