OK.
On Fri, Mar 2, 2018 at 12:36 PM, Marek Polacek <pola...@redhat.com> wrote:
> We ICE in cxx_eval_vec_init_1 whereby we try to initialize a flexible array
> member, because the code computing the number of elements of ATYPE wasn't
> prepared to handle arrays with no bounds. Fixed by using
> get_array_or_vector_nelts, broken out of existing code.
>
> Martin suggested to reject this code, but I decided to leave this as-is for
> now; we already reject code that actually tries to initialize the flexible
> array member with some data, e.g.:
>
> struct A {
> constexpr A() : i(), x("foo") {}
> int i;
> char x[];
> };
> A a;
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2018-03-02 Marek Polacek <pola...@redhat.com>
>
> PR c++/84578
> * constexpr.c (get_array_or_vector_nelts): New.
> (cxx_eval_array_reference): Use it.
> (cxx_eval_vec_init_1): Likewise.
> (cxx_eval_store_expression): Likewise.
>
> * g++.dg/ext/flexary29.C: New test.
>
> diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
> index 39e6cdfb33d..27f841db38f 100644
> --- gcc/cp/constexpr.c
> +++ gcc/cp/constexpr.c
> @@ -2300,6 +2300,32 @@ diag_array_subscript (const constexpr_ctx *ctx, tree
> array, tree index)
> }
> }
>
> +/* Return the number of elements for TYPE (which is an ARRAY_TYPE or
> + a VECTOR_TYPE). */
> +
> +static tree
> +get_array_or_vector_nelts (const constexpr_ctx *ctx, tree type,
> + bool *non_constant_p, bool *overflow_p)
> +{
> + tree nelts;
> + if (TREE_CODE (type) == ARRAY_TYPE)
> + {
> + if (TYPE_DOMAIN (type))
> + nelts = array_type_nelts_top (type);
> + else
> + nelts = size_zero_node;
> + }
> + else if (VECTOR_TYPE_P (type))
> + nelts = size_int (TYPE_VECTOR_SUBPARTS (type));
> + else
> + gcc_unreachable ();
> +
> + /* For VLAs, the number of elements won't be an integer constant. */
> + nelts = cxx_eval_constant_expression (ctx, nelts, false,
> + non_constant_p, overflow_p);
> + return nelts;
> +}
> +
> /* Extract element INDEX consisting of CHARS_PER_ELT chars from
> STRING_CST STRING. */
>
> @@ -2379,22 +2405,8 @@ cxx_eval_array_reference (const constexpr_ctx *ctx,
> tree t,
> }
> }
>
> - tree nelts;
> - if (TREE_CODE (TREE_TYPE (ary)) == ARRAY_TYPE)
> - {
> - if (TYPE_DOMAIN (TREE_TYPE (ary)))
> - nelts = array_type_nelts_top (TREE_TYPE (ary));
> - else
> - nelts = size_zero_node;
> - }
> - else if (VECTOR_TYPE_P (TREE_TYPE (ary)))
> - nelts = size_int (TYPE_VECTOR_SUBPARTS (TREE_TYPE (ary)));
> - else
> - gcc_unreachable ();
> -
> - /* For VLAs, the number of elements won't be an integer constant. */
> - nelts = cxx_eval_constant_expression (ctx, nelts, false, non_constant_p,
> - overflow_p);
> + tree nelts = get_array_or_vector_nelts (ctx, TREE_TYPE (ary),
> non_constant_p,
> + overflow_p);
> VERIFY_CONSTANT (nelts);
> if ((lval
> ? !tree_int_cst_le (index, nelts)
> @@ -2895,7 +2907,6 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree
> atype, tree init,
> bool *non_constant_p, bool *overflow_p)
> {
> tree elttype = TREE_TYPE (atype);
> - unsigned HOST_WIDE_INT max = tree_to_uhwi (array_type_nelts_top (atype));
> verify_ctor_sanity (ctx, atype);
> vec<constructor_elt, va_gc> **p = &CONSTRUCTOR_ELTS (ctx->ctor);
> bool pre_init = false;
> @@ -2924,6 +2935,9 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree
> atype, tree init,
> pre_init = true;
> }
>
> + tree nelts = get_array_or_vector_nelts (ctx, atype, non_constant_p,
> + overflow_p);
> + unsigned HOST_WIDE_INT max = tree_to_uhwi (nelts);
> for (i = 0; i < max; ++i)
> {
> tree idx = build_int_cst (size_type_node, i);
> @@ -3480,19 +3494,8 @@ cxx_eval_store_expression (const constexpr_ctx *ctx,
> tree t,
> case ARRAY_REF:
> tree nelts, ary;
> ary = TREE_OPERAND (probe, 0);
> - if (TREE_CODE (TREE_TYPE (ary)) == ARRAY_TYPE)
> - {
> - if (TYPE_DOMAIN (TREE_TYPE (ary)))
> - nelts = array_type_nelts_top (TREE_TYPE (ary));
> - else
> - nelts = size_zero_node;
> - }
> - else if (VECTOR_TYPE_P (TREE_TYPE (ary)))
> - nelts = size_int (TYPE_VECTOR_SUBPARTS (TREE_TYPE (ary)));
> - else
> - gcc_unreachable ();
> - nelts = cxx_eval_constant_expression (ctx, nelts, false,
> - non_constant_p, overflow_p);
> + nelts = get_array_or_vector_nelts (ctx, TREE_TYPE (ary),
> + non_constant_p, overflow_p);
> VERIFY_CONSTANT (nelts);
> gcc_assert (TREE_CODE (nelts) == INTEGER_CST
> && TREE_CODE (TREE_OPERAND (probe, 1)) == INTEGER_CST);
> diff --git gcc/testsuite/g++.dg/ext/flexary29.C
> gcc/testsuite/g++.dg/ext/flexary29.C
> index e69de29bb2d..a696fd9804f 100644
> --- gcc/testsuite/g++.dg/ext/flexary29.C
> +++ gcc/testsuite/g++.dg/ext/flexary29.C
> @@ -0,0 +1,12 @@
> +// PR c++/84578
> +// { dg-do compile { target c++11 } }
> +// { dg-options -Wno-pedantic }
> +
> +struct A
> +{
> + constexpr A() : i(), x() {}
> + int i;
> + char x[];
> +};
> +
> +A a;
>
> Marek
