[PATCH] Fix aliasing violation in __vfscanf_internal [BZ #26690]

[Adhemerval Zanella]

On 07/10/2020 15:08, Florian Weimer wrote:
> * Szabolcs Nagy via Libc-alpha:
> 
>> diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c
>> index 95b46dcbeb..d832493623 100644
>> --- a/stdio-common/vfscanf-internal.c
>> +++ b/stdio-common/vfscanf-internal.c
>> @@ -135,6 +135,16 @@
>>  
>>  #include "printf-parse.h" /* Use read_int.  */
>>  
>> +/* Same as read_int, but for CHAR_T * instead of UCHAR_T * string.  */
>> +static int
>> +read_int_char (const CHAR_T * *pstr)
>> +{
>> +  const UCHAR_T *ustr = (const UCHAR_T *) *pstr;
>> +  int retval = read_int (&ustr);
>> +  *pstr = (const CHAR_T *) ustr;
>> +  return retval;
>> +}
>> +
>>  #define encode_error() do {						      \
>>  			  __set_errno (EILSEQ);				      \
>>  			  goto errout;					      \
>> @@ -486,7 +496,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
>>        /* Check for a positional parameter specification.  */
>>        if (ISDIGIT ((UCHAR_T) *f))
>>  	{
>> -	  argpos = read_int ((const UCHAR_T **) &f);
>> +	  argpos = read_int_char (&f);
>>  	  if (*f == L_('$'))
>>  	    ++f;
>>  	  else
>> @@ -522,7 +532,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
>>        /* Find the maximum field width.  */
>>        width = 0;
>>        if (ISDIGIT ((UCHAR_T) *f))
>> -	width = read_int ((const UCHAR_T **) &f);
>> +	width = read_int_char (&f);
>>      got_width:
>>        if (width == 0)
>>  	width = -1;
> 
> Patch and commit message look reasonable to me.  Thanks.
> 

Andreas has sent a similar fix for the same issue [1]. Is it something
wrong with his fix? It seems to cover more aliasing violation 

[1] https://sourceware.org/pipermail/libc-alpha/2020-October/118149.html