[PATCH] vfprintf: Use struct scratch_buffer for positional arguments allocation

[Adhemerval Zanella]

On 19/06/2017 13:19, Florian Weimer wrote:
> 2017-06-19  Florian Weimer  <fweimer@redhat.com>
> 
> 	* stdio-common/vfprintf.c (printf_positional): Use struct
> 	scratch_buffer to allocate backing storage for the args_value,
> 	args_size, args_type arrays.
> 


> -  /* Set up the remaining two arrays to each point past the end of the
> -     prior array, since space for all three has been allocated now.  */
> -  args_size = &args_value[nargs].pa_int;
> -  args_type = &args_size[nargs];
> -  memset (args_type, s->_flags2 & _IO_FLAGS2_FORTIFY ? '\xff' : '\0',
> -	  nargs * sizeof (*args_type));
> +  union printf_arg *args_value;
> +  int *args_size;
> +  int *args_type;
> +  {
> +    /* Calculate total size needed to represent a single argument
> +       across all three argument-related arrays.  */
> +    size_t bytes_per_arg
> +      = sizeof (*args_value) + sizeof (*args_size) + sizeof (*args_type);

LGTM, although I do not see much gain for using brackets just for 
bytes_per_arg.

> +    if (!scratch_buffer_set_array_size (&argsbuf, nargs, bytes_per_arg))
> +      {
> +	done = -1;
> +	goto all_done;
> +      }
> +    args_value = argsbuf.data;
> +    /* Set up the remaining two arrays to each point past the end of
> +       the prior array, since space for all three has been allocated
> +       now.  */
> +    args_size = &args_value[nargs].pa_int;
> +    args_type = &args_size[nargs];
> +    memset (args_type, s->_flags2 & _IO_FLAGS2_FORTIFY ? '\xff' : '\0',
> +	    nargs * sizeof (*args_type));
> +  }
>  
>    /* XXX Could do sanity check here: If any element in ARGS_TYPE is
>       still zero after this loop, format is invalid.  For now we
> @@ -1966,8 +1955,7 @@ printf_positional (_IO_FILE *s, const CHAR_T *format, int readonly_format,
>  		 - specs[nspecs_done].end_of_fmt);
>      }
>   all_done:
> -  if (__glibc_unlikely (args_malloced != NULL))
> -    free (args_malloced);
> +  scratch_buffer_free (&argsbuf);
>    scratch_buffer_free (&specsbuf);
>    return done;
>  }
>