[PATCH] c++: suppress all warnings on memper pointers to work around dICE [PR101219]

[Sergei Trofimovich via Gcc-patches]

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.

        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.
---
 gcc/cp/typeck.c                         |  6 +++++-
 gcc/testsuite/g++.dg/torture/pr101219.C | 10 ++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/torture/pr101219.C

diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index a483e1f988d..aa91fd21c7b 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -3326,7 +3326,11 @@ build_ptrmemfunc_access_expr (tree ptrmem, tree 
member_name)
        member = DECL_CHAIN (member))
     if (DECL_NAME (member) == member_name)
       break;
-  return build_simple_component_ref (ptrmem, member);
+  tree r = build_simple_component_ref (ptrmem, member);
+  /* Suppress warning to avoid exposing missing BINFO for ptrmem
+     synthetic structs: PR101219.  */
+  suppress_warning(r);
+  return r;
 }
 
 /* Given an expression PTR for a pointer, return an expression
diff --git a/gcc/testsuite/g++.dg/torture/pr101219.C 
b/gcc/testsuite/g++.dg/torture/pr101219.C
new file mode 100644
index 00000000000..c8d30448187
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr101219.C
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-Wall" } */
+struct S { void m(); };
+
+template <int> bool f() {
+  /* In PR101219 gcc used to ICE in warning code. */
+  void (S::*mp)();
+
+  return &S::m == mp;
+}
-- 
2.32.0