On Wed, 11 Aug 2021 15:19:58 -0400
Jason Merrill <ja...@redhat.com> wrote:
> On 8/6/21 11:34 AM, Sergei Trofimovich wrote:
> > 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)
>
> Generally it's desirable to diagnose templates for which no valid
> instantiation is possible. It seems reasonable in most cases to also
> warn about templates for which all instantiations would warn.
>
> But uninitialized warnings rely on flow analysis that we only do on
> instantiated functions, and in any case the ICE doesn't depend on mp
> being uninitialized; I get the same crash if I add = 0 to the declaration.
Aha. That makes sense. Let's just fix ICE then.
> > + if (object_type && TYPE_PTRMEMFUNC_P(object_type)
>
> Missing space before (.
>
> > + && TREE_CODE (member) == FIELD_DECL)
> > + {
> > + r = build_ptrmemfunc_access_expr (object, DECL_NAME(member));
>
> And here.
Added both. Attached as v3.
--
Sergei
>From dbb17a22383faa7837bdd2ea9c902bfab53fa8f2 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <siarh...@google.com>
Date: Fri, 6 Aug 2021 16:14:16 +0100
Subject: [PATCH v3] 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.
---
Change since v2: fix whitespace around macros.
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..42ea51cebc0 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
