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* [gcc r11-3295] c++: std::is_constant_evaluated inside constraint [PR97051]
@ 2020-09-19 15:18 Patrick Palka
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From: Patrick Palka @ 2020-09-19 15:18 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:dea470d09155f2007bdd502c16614128cb6f9348
commit r11-3295-gdea470d09155f2007bdd502c16614128cb6f9348
Author: Patrick Palka <ppalka@redhat.com>
Date: Sat Sep 19 11:17:41 2020 -0400
c++: std::is_constant_evaluated inside constraint [PR97051]
According to [expr.const]/14, the result of substitution into an atomic
constraint is manifestly constant-evaluated; this patch adjusts the call
to maybe_constant_value in satisfy_atom to that effect.
gcc/cp/ChangeLog:
PR c++/97051
* constraint.cc (satisfy_atom): Pass true as the
manifestly_const_eval argument to maybe_constant_value.
gcc/testsuite/ChangeLog:
PR c++/97051
* g++.dg/cpp2a/is-constant-evaluated11.C: New test.
Diff:
---
gcc/cp/constraint.cc | 3 ++-
gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated11.C | 16 ++++++++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 0aab3073cc1..8137df59e37 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2643,7 +2643,8 @@ satisfy_atom (tree t, tree args, subst_info info)
result = cxx_constant_value (result);
else
{
- result = maybe_constant_value (result);
+ result = maybe_constant_value (result, NULL_TREE,
+ /*manifestly_const_eval=*/true);
if (!TREE_CONSTANT (result))
result = error_mark_node;
}
diff --git a/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated11.C b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated11.C
new file mode 100644
index 00000000000..a31867f74fb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated11.C
@@ -0,0 +1,16 @@
+// PR c++/97051
+// { dg-do compile { target c++20 } }
+
+namespace std {
+ constexpr inline bool
+ is_constant_evaluated () noexcept
+ {
+ return __builtin_is_constant_evaluated ();
+ }
+}
+
+template<typename>
+ requires (std::is_constant_evaluated())
+constexpr int a = 0;
+
+constexpr int b = a<int>;
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