On 7/7/21 9:40 PM, Marek Polacek wrote:
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. Only checking cp_unevaluated_operand therein does
not work, because expr_noexcept_p can be called in an unevaluated
context, so I resorted to the following cp_evaluated hack. Does
that seem acceptable?
I suppose, but why not check for SIZEOF_EXPR/ALIGNOF_EXPR/NOEXCEPT_EXPR
directly?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/101087
gcc/cp/ChangeLog:
* except.c (check_noexcept_r): Don't walk into unevaluated
operands.
(expr_noexcept_p): Use cp_evaluated.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept70.C: New test.
---
gcc/cp/except.c | 14 +++++++++++---
gcc/testsuite/g++.dg/cpp0x/noexcept70.C | 5 +++++
2 files changed, 16 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept70.C
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index a8cea53cf91..6f97ac40b4b 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1033,12 +1033,15 @@ 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 (cp_unevaluated_operand)
+ *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
@@ -1155,6 +1158,11 @@ expr_noexcept_p (tree expr, tsubst_flags_t complain)
if (expr == error_mark_node)
return false;
+ /* Even though the operand of noexcept is an _unevaluated_ operand,
+ temporarily clearing cp_unevaluated_operand allows us to check it
+ in check_noexcept_r, to handle noexcept(sizeof(f())). It could be
+ set when we are called in the context of synthesized_method_walk. */
+ cp_evaluated ev;
fn = cp_walk_tree_without_duplicates (&expr, check_noexcept_r, 0);
if (fn)
{
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())), "");
base-commit: a110855667782dac7b674d3e328b253b3b3c919b
