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* [gcc r11-8709] c++: Fix noexcept with unevaluated operand [PR101087]
@ 2021-07-08 21:48 Marek Polacek
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From: Marek Polacek @ 2021-07-08 21:48 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:cbef732522568f8adce46c472b16391c864d0fd0
commit r11-8709-gcbef732522568f8adce46c472b16391c864d0fd0
Author: Marek Polacek <polacek@redhat.com>
Date: Wed Jul 7 20:02:18 2021 -0400
c++: Fix noexcept with unevaluated operand [PR101087]
It sounds plausible that this assert
int f();
static_assert(noexcept(sizeof(f())));
should pass: sizeof produces a std::size_t and its operand is not
evaluated, so it can't throw. noexcept should only evaluate to
false for potentially evaluated operands. Therefore I think that
check_noexcept_r shouldn't walk into operands of sizeof/decltype/
alignof/typeof.
PR c++/101087
gcc/cp/ChangeLog:
* cp-tree.h (unevaluated_p): New.
* except.c (check_noexcept_r): Use it. Don't walk into
unevaluated operands.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept70.C: New test.
(cherry picked from commit dee00bf6894be0cabb8f263c993357a6f8444f8b)
Diff:
---
gcc/cp/cp-tree.h | 13 +++++++++++++
gcc/cp/except.c | 9 ++++++---
gcc/testsuite/g++.dg/cpp0x/noexcept70.C | 5 +++++
3 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 877ed1c1c65..bdc33a79241 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -8429,6 +8429,19 @@ is_constrained_auto (const_tree t)
return is_auto (t) && PLACEHOLDER_TYPE_CONSTRAINTS_INFO (t);
}
+/* True if CODE, a tree code, denotes a tree whose operand is not evaluated
+ as per [expr.context], i.e., an operand to sizeof, typeof, decltype, or
+ alignof. */
+
+inline bool
+unevaluated_p (tree_code code)
+{
+ return (code == DECLTYPE_TYPE
+ || code == ALIGNOF_EXPR
+ || code == SIZEOF_EXPR
+ || code == NOEXCEPT_EXPR);
+}
+
/* RAII class to push/pop class scope T; if T is not a class, do nothing. */
struct push_nested_class_guard
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index cbafc09629b..bc260d145d1 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1032,12 +1032,15 @@ check_handlers (tree handlers)
expression whose type is a polymorphic class type (10.3). */
static tree
-check_noexcept_r (tree *tp, int * /*walk_subtrees*/, void * /*data*/)
+check_noexcept_r (tree *tp, int *walk_subtrees, void *)
{
tree t = *tp;
enum tree_code code = TREE_CODE (t);
- if ((code == CALL_EXPR && CALL_EXPR_FN (t))
- || code == AGGR_INIT_EXPR)
+
+ if (unevaluated_p (code))
+ *walk_subtrees = false;
+ else if ((code == CALL_EXPR && CALL_EXPR_FN (t))
+ || code == AGGR_INIT_EXPR)
{
/* We can only use the exception specification of the called function
for determining the value of a noexcept expression; we can't use
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept70.C b/gcc/testsuite/g++.dg/cpp0x/noexcept70.C
new file mode 100644
index 00000000000..45a6137dd6f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept70.C
@@ -0,0 +1,5 @@
+// PR c++/101087
+// { dg-do compile { target c++11 } }
+
+int f();
+static_assert(noexcept(sizeof(f())), "");
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