On Mon, 23 Mar 2020, Jason Merrill wrote:
> On 3/22/20 5:14 PM, Patrick Palka wrote:
> > In this PR we're emitting -Wnoexcept warnings about potentially-throwing
> > NSDMIs
> > when computing the noexcept specification of a class's defaulted default
> > constructor. Alhough these warnings are in some sense valid, this patch
> > takes
> > the route of suppressing them, because:
> >
> > 1. the warning message is confusing in its current form;
> > 2. warning for 'struct C { B b = B(); };' but not for 'struct C { B b;
> > };'
> > is inconsistent; and
> > 3. emitting a warning here arguably doesn't fall under the umbrella of
> > -Wnoexcept, whose documentation says it warns only when a
> > noexcept-expression evaluates to false, but there are
> > noexcept-expressions
> > here.
> >
> > Tested on x86_64-pc-linux-gnu, does this look OK to commit?
>
> Let's add a comment to maybe_noexcept_warning suggesting that we might in
> future want to do something like walk_subtrees in the case of a defaulted
> function. OK with that change.
>
> Jason
Thanks, patch committed with a comment to that effect added to
maybe_noexcept_warning. Here is the final patch:
-- >8 --
gcc/cp/ChangeLog:
PR c++/93805
* except.c (maybe_noexcept_warning): Add TODO comment.
* method.c (walk_field_subobs): Pass tf_none to expr_noexcept_p.
gcc/testsuite/ChangeLog:
PR c++/93805
* g++.dg/warn/Wnoexcept2.C: New test.
---
gcc/cp/ChangeLog | 6 ++++++
gcc/cp/except.c | 5 ++++-
gcc/cp/method.c | 2 +-
gcc/testsuite/ChangeLog | 5 +++++
gcc/testsuite/g++.dg/warn/Wnoexcept2.C | 15 +++++++++++++++
5 files changed, 31 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wnoexcept2.C
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 3340f47d506..59db03c0b07 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-23 Patrick Palka <ppa...@redhat.com>
+
+ PR c++/93805
+ * except.c (maybe_noexcept_warning): Add TODO.
+ * method.c (walk_field_subobs): Pass tf_none to expr_noexcept_p.
+
2020-03-23 nathans <nat...@acm.org>
PR c++/94044
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 262ba5d309c..7e93c51f9ea 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1160,7 +1160,10 @@ struct GTY(()) pending_noexcept {
static GTY(()) vec<pending_noexcept, va_gc> *pending_noexcept_checks;
/* FN is a FUNCTION_DECL that caused a noexcept-expr to be false. Warn if
- it can't throw. */
+ it can't throw.
+
+ TODO: Consider extending -Wnoexcept to do something like walk_subtrees in
the
+ case of a defaulted function that obtained a noexcept(false) spec. */
static void
maybe_noexcept_warning (tree fn)
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index c131fd41536..41b9ff86bdd 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1988,7 +1988,7 @@ walk_field_subobs (tree fields, special_function_kind
sfk, tree fnname,
if (nsdmi == error_mark_node)
*spec_p = error_mark_node;
else if (*spec_p != error_mark_node
- && !expr_noexcept_p (nsdmi, complain))
+ && !expr_noexcept_p (nsdmi, tf_none))
*spec_p = noexcept_false_spec;
}
/* Don't do the normal processing. */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1d053e07721..5f079f1fca9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-23 Patrick Palka <ppa...@redhat.com>
+
+ PR c++/93805
+ * g++.dg/warn/Wnoexcept2.C: New test.
+
2020-03-23 Jakub Jelinek <ja...@redhat.com>
PR c++/91993
diff --git a/gcc/testsuite/g++.dg/warn/Wnoexcept2.C
b/gcc/testsuite/g++.dg/warn/Wnoexcept2.C
new file mode 100644
index 00000000000..60541be3575
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wnoexcept2.C
@@ -0,0 +1,15 @@
+// PR c++/93805
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wnoexcept" }
+
+struct B
+{
+ B() {}
+};
+
+struct C
+{
+ B b = B();
+};
+
+C c; // { dg-bogus "noexcept-expression" }
--
2.26.0.rc1.11.g30e9940356
