c-format: double vs float

[Jakub Jelinek]

On Fri, Jan 08, 2010 at 02:52:45PM -0500, DJ Delorie wrote:
> 
> This one is a worry... when we pass float to printf() on a target
> where doubles and floats are the same size (h8300-elf for example),
> the normal float->double type promotion doesn't happen (nor does it
> need to) but c-format now complains that a float is passed where a
> double is expected (which is true).  Is the code technically correct,
> but still wrong?  Is gcc trying too hard to be pedantic in this case?
> Is the test I wrote sufficient?
> 
>   float x;
>   printf("%f", x);

As we warn even for say:
void foo (long long x)
{
  printf ("%lx\n", x);
}
when sizeof (long) == sizeof (long long), we should warn about the above
as well.  So IMHO the patch is wrong.  The if stmt before this one is just
used for M$ I32/I64 formats, nothing else.

> 
> 	* c-format.c (check_format_types): As a special case, check for
> 	targets where sizeof(double) == sizeof(float) and thus no
> 	promotion happens.
> 
> Index: c-format.c
> ===================================================================
> --- c-format.c	(revision 155741)
> +++ c-format.c	(working copy)
> @@ -2272,12 +2272,18 @@ check_format_types (format_wanted_type *
>        if (types->scalar_identity_flag
>  	  && (TREE_CODE (cur_type) == TREE_CODE (wanted_type)
>  	      || (INTEGRAL_TYPE_P (cur_type)
>  		  && INTEGRAL_TYPE_P (wanted_type)))
>  	  && TYPE_PRECISION (cur_type) == TYPE_PRECISION (wanted_type))
>  	continue;
> +      /* For targets where sizeof(float) == sizeof(double), the usual
> +	 float->double type promotion doesn't happen, but the user's
> +	 code is technically correct.  */
> +      if (cur_type == float_type_node && wanted_type == double_type_node
> +	  && TYPE_PRECISION (cur_type) == TYPE_PRECISION (wanted_type))
> +	continue;
>        /* Now we have a type mismatch.  */
>        format_type_warning (types->name, format_start, format_length,
>  			   wanted_type, types->pointer_count,
>  			   types->wanted_type_name, orig_cur_type, arg_num);
>      }
>  }

	Jakub