Re: [PATCH, PR 57748] Set mode of structures with zero sized arrays to be BLK

[David Abdurachmanov <david dot abd at gmail dot com>]

ping^2

david

On Aug 12, 2013, at 2:31 PM, David Abdurachmanov wrote:

> Hi,
> 
> Ping. Any news of the following patch being included into the trunk?
> 
> Thanks,
> david
> 
> On Aug 2, 2013, at 1:45 PM, Martin Jambor wrote:
> 
>> Hi,
>> 
>> while compute_record_mode in stor-layout.c makes sure it assigns BLK
>> mode to structs with flexible arrays, it has no such provisions for
>> zero length arrays
>> (http://gcc.gnu.org/onlinedocs/gcc-4.8.1/gcc/Zero-Length.html).  I
>> think that in order to avoid problems and surprises like PR 57748
>> (where this triggered code that was intended for small structures that
>> fit into a scalar mode and ICEd), we should assign both variable array
>> possibilities the same mode.
>> 
>> Bootstrapped and tested on x86_64-linux without any problems.  OK for
>> trunk and the 4.8 branch?  (I'm not sure about the 4.7, this PR does
>> not happen there despite the wrong mode so I'd ignore it for now.)
>> 
>> Thanks,
>> 
>> Martin
>> 
>> 
>> 2013-08-01  Martin Jambor  <mjambor@suse.cz>
>> 
>> 	PR middle-end/57748
>> 	* stor-layout.c (compute_record_mode): Treat zero-sized array fields
>> 	like incomplete types.
>> 
>> testsuite/
>> 	* gcc.dg/torture/pr57748.c: New test.
>> 
>> 
>> *** /tmp/lV6Ba8_stor-layout.c	Thu Aug  1 16:28:25 2013
>> --- gcc/stor-layout.c	Thu Aug  1 15:36:18 2013
>> *************** compute_record_mode (tree type)
>> *** 1604,1610 ****
>> 		   && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
>> 	  || ! host_integerp (bit_position (field), 1)
>> 	  || DECL_SIZE (field) == 0
>> ! 	  || ! host_integerp (DECL_SIZE (field), 1))
>> 	return;
>> 
>>       /* If this field is the whole struct, remember its mode so
>> --- 1604,1612 ----
>> 		   && integer_zerop (TYPE_SIZE (TREE_TYPE (field)))))
>> 	  || ! host_integerp (bit_position (field), 1)
>> 	  || DECL_SIZE (field) == 0
>> ! 	  || ! host_integerp (DECL_SIZE (field), 1)
>> ! 	  || (TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE
>> ! 	      && tree_low_cst (DECL_SIZE (field), 1) == 0))
>> 	return;
>> 
>>       /* If this field is the whole struct, remember its mode so
>> *** /dev/null	Tue Jun  4 12:34:56 2013
>> --- gcc/testsuite/gcc.dg/torture/pr57748.c	Thu Aug  1 15:42:14 2013
>> ***************
>> *** 0 ****
>> --- 1,45 ----
>> + /* PR middle-end/57748 */
>> + /* { dg-do run } */
>> + 
>> + #include <stdlib.h>
>> + 
>> + extern void abort (void);
>> + 
>> + typedef long long V
>> +   __attribute__ ((vector_size (2 * sizeof (long long)), may_alias));
>> + 
>> + typedef struct S { V a; V b[0]; } P __attribute__((aligned (1)));
>> + 
>> + struct __attribute__((packed)) T { char c; P s; };
>> + 
>> + void __attribute__((noinline, noclone))
>> + check (struct T *t)
>> + {
>> +   if (t->s.b[0][0] != 3 || t->s.b[0][1] != 4)
>> +     abort ();
>> + }
>> + 
>> + int __attribute__((noinline, noclone))
>> + get_i (void)
>> + {
>> +   return 0;
>> + }
>> + 
>> + void __attribute__((noinline, noclone))
>> + foo (P *p)
>> + {
>> +   V a = { 3, 4 };
>> +   int i = get_i();
>> +   p->b[i] = a;
>> + }
>> + 
>> + int
>> + main ()
>> + {
>> +   struct T *t = (struct T *) malloc (128);
>> + 
>> +   foo (&t->s);
>> +   check (t);
>> + 
>> +   return 0;
>> + }
>