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
