Re: [C++ PATCH] Reuse certain cxx_eval_constant_expression results in cxx_eval_vec_init_1 (PR c++/70001)

[Jason Merrill <jason at redhat dot com>]

On 03/10/2016 01:39 PM, Jakub Jelinek wrote:
> +      /* Don't reuse the result of cxx_eval_constant_expression
> +	 call if it isn't a constant initializer or if it requires
> +	 relocations.  */

Let's phrase this positively ("Reuse the result if...").

> +	  if (new_ctx.ctor != ctx->ctor)
> +	    eltinit = new_ctx.ctor;
> +	  for (i = 1; i < max; ++i)
> +	    {
> +	      idx = build_int_cst (size_type_node, i);
> +	      CONSTRUCTOR_APPEND_ELT (*p, idx, eltinit);
> +	    }

This is going to use the same CONSTRUCTOR for all the elements, which 
will lead to problems if we then store into a subobject of one of the 
elements and see that reflected in all the others as well.  We need to 
unshare_expr when reusing the initializer.

Jason