On Thu, 29 Jul 2021 11:41:39 -0400
Jason Merrill <ja...@redhat.com> wrote:
> On 7/22/21 7:15 PM, Sergei Trofimovich wrote:
> > From: Sergei Trofimovich <siarh...@google.com>
> >
> > r12-1804 ("cp: add support for per-location warning groups.") among other
> > things removed warning suppression from a few places including ptrmemfuncs.
> >
> > Currently ptrmemfuncs don't have valid BINFO attached which causes ICEs
> > in access checks:
> >
> > crash_signal
> > gcc/toplev.c:328
> > perform_or_defer_access_check(tree_node*, tree_node*, tree_node*, int,
> > access_failure_info*)
> > gcc/cp/semantics.c:490
> > finish_non_static_data_member(tree_node*, tree_node*, tree_node*)
> > gcc/cp/semantics.c:2208
> > ...
> >
> > The change suppresses warnings again until we provide BINFOs for
> > ptrmemfuncs.
>
> We don't need BINFOs for PMFs, we need to avoid paths that expect them.
>
> It looks like the problem is with tsubst_copy_and_build calling
> finish_non_static_data_member instead of build_ptrmemfunc_access_expr.
Sounds good. I'm not sure what would be the best way to match it. Here is
my attempt seems to survive all regtests:
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20530,7 +20530,13 @@ tsubst_copy_and_build (tree t,
if (member == error_mark_node)
RETURN (error_mark_node);
- if (TREE_CODE (member) == FIELD_DECL)
+ if (object_type && TYPE_PTRMEMFUNC_P(object_type)
+ && TREE_CODE (member) == FIELD_DECL)
+ {
+ r = build_ptrmemfunc_access_expr (object, DECL_NAME(member));
+ RETURN (r);
+ }
+ else if (TREE_CODE (member) == FIELD_DECL)
{
r = finish_non_static_data_member (member, object, NULL_TREE);
if (TREE_CODE (r) == COMPONENT_REF)
> > PR c++/101219
> >
> > gcc/cp/ChangeLog:
> >
> > * typeck.c (build_ptrmemfunc_access_expr): Suppress all warnings
> > to avoid ICE.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/torture/pr101219.C: New test.
>
> This doesn't need to be in torture; it has nothing to do with optimization.
Aha, moved to gcc/testsuite/g++.dg/warn/pr101219.C.
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/pr101219.C
@@ -0,0 +1,11 @@
+/* PR c++/101219 - ICE on use of uninitialized memfun pointer
+ { dg-do compile }
+ { dg-options "-Wall" } */
+
+struct S { void m(); };
+
+template <int> bool f() {
+ void (S::*mp)();
+
+ return &S::m == mp; // no warning emitted here (no instantiation)
+}
Another question: Is it expected that gcc generates no warnings here?
It's an uninstantiated function (-1 for warn), but from what I
understand it's guaranteed to generate comparison with uninitialized
data if it ever gets instantiated. Given that we used to ICE in
warning code gcc could possibly flag it? (+1 for warn)
Attached full patch as well. Full 'make check' shows no regressions on
x86_64-linux.
--
Sergei
>From 9c51dbc598d8633167729de9637c8cdb5f3089fe Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <siarh...@google.com>
Date: Fri, 6 Aug 2021 16:14:16 +0100
Subject: [PATCH v2] c++: fix ptrmemfunc template instantiation [PR101219]
r12-1804 ("cp: add support for per-location warning groups.") among other
things removed warning suppression from a few places including ptrmemfuncs.
This exposed a bug in warning detection code as a reference to missing
BINFO (it's intentionally missing for ptrmemfunc types):
crash_signal
gcc/toplev.c:328
perform_or_defer_access_check(tree_node*, tree_node*, tree_node*, int, access_failure_info*)
gcc/cp/semantics.c:490
finish_non_static_data_member(tree_node*, tree_node*, tree_node*)
gcc/cp/semantics.c:2208
...
The change special cases ptrmemfuncs in templace substitution by using
build_ptrmemfunc_access_expr() instead of finish_non_static_data_member().
PR c++/101219
gcc/cp/ChangeLog:
* pt.c (tsubst_copy_and_build): Use build_ptrmemfunc_access_expr
to construct ptrmemfunc expression instantiation.
gcc/testsuite/ChangeLog:
* g++.dg/warn/pr101219.C: New test.
Signed-off-by: Sergei Trofimovich <siarh...@google.com>
---
gcc/cp/pt.c | 8 +++++++-
gcc/testsuite/g++.dg/warn/pr101219.C | 11 +++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/warn/pr101219.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index b396ddd0089..c7a0317cbfb 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20530,7 +20530,13 @@ tsubst_copy_and_build (tree t,
if (member == error_mark_node)
RETURN (error_mark_node);
- if (TREE_CODE (member) == FIELD_DECL)
+ if (object_type && TYPE_PTRMEMFUNC_P(object_type)
+ && TREE_CODE (member) == FIELD_DECL)
+ {
+ r = build_ptrmemfunc_access_expr (object, DECL_NAME(member));
+ RETURN (r);
+ }
+ else if (TREE_CODE (member) == FIELD_DECL)
{
r = finish_non_static_data_member (member, object, NULL_TREE);
if (TREE_CODE (r) == COMPONENT_REF)
diff --git a/gcc/testsuite/g++.dg/warn/pr101219.C b/gcc/testsuite/g++.dg/warn/pr101219.C
new file mode 100644
index 00000000000..0d23d73c9ec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/pr101219.C
@@ -0,0 +1,11 @@
+/* PR c++/101219 - ICE on use of uninitialized memfun pointer
+ { dg-do compile }
+ { dg-options "-Wall" } */
+
+struct S { void m(); };
+
+template <int> bool f() {
+ void (S::*mp)();
+
+ return &S::m == mp; // no warning emitted here (no instantiation)
+}
--
2.32.0
