Re: [PATCH] Fix middle-end/81737

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Aug 07, 2017 at 10:47:51AM +0200, Marek Polacek wrote:
> In my recent change I failed to check whether the type domain
> of a type is non-NULL and this goof causes crashing on this
> testcase.
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> 2017-08-07  Marek Polacek  <polacek@redhat.com>
> 
> 	PR middle-end/81737
> 	* fold-const.c (fold_indirect_ref_1): Check type_domain.
> 
> 	* gcc.dg/pr81737.c: New test.

The old code was assuming size_zero_node if type_domain is NULL
or TYPE_MIN_VALUE is NULL, which is reasonable for C/C++, but indeed might
be wrong perhaps for Fortran or Ada.

Hopefully nothing will assume this has to be folded in these cases (mainly
thinking about C++ constexpr).

So ok.

> diff --git gcc/fold-const.c gcc/fold-const.c
> index d563ba76766..8eaea6cce3a 100644
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -14107,8 +14107,10 @@ fold_indirect_ref_1 (location_t loc, tree type, tree op0)
>  		   && type == TREE_TYPE (op00type))
>  	    {
>  	      tree type_domain = TYPE_DOMAIN (op00type);
> -	      tree min = TYPE_MIN_VALUE (type_domain);
> -	      if (min && TREE_CODE (min) == INTEGER_CST)
> +	      tree min;
> +	      if (type_domain != NULL_TREE
> +		  && (min = TYPE_MIN_VALUE (type_domain))
> +		  && TREE_CODE (min) == INTEGER_CST)
>  		{
>  		  offset_int off = wi::to_offset (op01);
>  		  offset_int el_sz = wi::to_offset (TYPE_SIZE_UNIT (type));
> diff --git gcc/testsuite/gcc.dg/pr81737.c gcc/testsuite/gcc.dg/pr81737.c
> index e69de29bb2d..493358956ef 100644
> --- gcc/testsuite/gcc.dg/pr81737.c
> +++ gcc/testsuite/gcc.dg/pr81737.c
> @@ -0,0 +1,6 @@
> +/* PR middle-end/81737 */
> +/* { dg-do compile } */
> +/* { dg-options "" } */
> +
> +extern int a[];
> +void fn1() { (a + 0)[1]; }
> 
> 	Marek

	Jakub