On Mon, Dec 18, 2017 at 01:07:18PM -0500, Jason Merrill wrote:
> On Mon, Dec 18, 2017 at 10:09 AM, Marek Polacek <pola...@redhat.com> wrote:
> > Here the problem was that cxx_eval_call_expression can cache the result of a
> > constexpr call in constexpr_call_table, but we have to be careful, after
> > store_init_value the result might be invalid. So I believe we also have to
> > clear the constexpr call table. I've lumped it together with clearing
> > cv_cache.
>
> Hmm, that seems like a big hammer; the problem isn't that
> store_init_value makes the result invalid, it's that the result
> calculated during store_init_value (when we can treat the object as
> constant) isn't relevant later (when the object is no longer
> constant). So we want to avoid caching when we're called for the
> initial value. Maybe by changing
>
> if (depth_ok && !non_constant_args)
>
> to
>
> if (depth_ok && !non_constant_args && ctx->strict)
>
> ? Does that work?
Yes! I wish I'd thought of ctx->strict before. Well, something to remember.
Bootstrapped/regtested on x86_64-linux, ok for trunk/7?
2017-12-18 Marek Polacek <pola...@redhat.com>
PR c++/83116
* constexpr.c (cxx_eval_call_expression): Only look into
constexpr_call_table if ctx->strict.
* g++.dg/cpp1y/constexpr-83116.C: New test.
diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index 0455be1d6da..518798e0c43 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -1588,7 +1588,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
tree result = NULL_TREE;
constexpr_call *entry = NULL;
- if (depth_ok && !non_constant_args)
+ if (depth_ok && !non_constant_args && ctx->strict)
{
new_call.hash = iterative_hash_template_arg
(new_call.bindings, constexpr_fundef_hasher::hash (new_call.fundef));
diff --git gcc/testsuite/g++.dg/cpp1y/constexpr-83116.C
gcc/testsuite/g++.dg/cpp1y/constexpr-83116.C
index e69de29bb2d..18d79e2e1cc 100644
--- gcc/testsuite/g++.dg/cpp1y/constexpr-83116.C
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-83116.C
@@ -0,0 +1,18 @@
+// PR c++/83116
+// { dg-do run { target c++14 } }
+// { dg-options "-O2" }
+
+struct S {
+ constexpr S () : s(0) { foo (); }
+ constexpr int foo () { return s; }
+ int s;
+};
+
+int
+main ()
+{
+ static S var;
+ var.s = 5;
+ if (var.s != 5 || var.foo () != 5)
+ __builtin_abort ();
+}
Marek
