Hi!

On the following testcase, we emit false positive warnings/errors about using
the deprecated or unavailable methods when creating thunks for them, even
when nothing (in the testcase so far) actually used those.

The following patch temporarily disables that diagnostics when creating
the thunks.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-09-11  Jakub Jelinek  <ja...@redhat.com>

        PR c++/116636
        * method.cc: Include decl.h.
        (use_thunk): Temporarily change deprecated_state to
        UNAVAILABLE_DEPRECATED_SUPPRESS.

        * g++.dg/warn/deprecated-19.C: New test.

--- gcc/cp/method.cc.jj 2024-09-06 13:43:37.823301244 +0200
+++ gcc/cp/method.cc    2024-09-11 12:19:57.420486173 +0200
@@ -26,6 +26,7 @@ along with GCC; see the file COPYING3.
 #include "coretypes.h"
 #include "target.h"
 #include "cp-tree.h"
+#include "decl.h"
 #include "stringpool.h"
 #include "cgraph.h"
 #include "varasm.h"
@@ -283,6 +284,11 @@ use_thunk (tree thunk_fndecl, bool emit_
   /* Thunks are always addressable; they only appear in vtables.  */
   TREE_ADDRESSABLE (thunk_fndecl) = 1;
 
+  /* Don't diagnose deprecated or unavailable functions just because they
+     have thunks emitted for them.  */
+  auto du = make_temp_override (deprecated_state,
+                                UNAVAILABLE_DEPRECATED_SUPPRESS);
+
   /* Figure out what function is being thunked to.  It's referenced in
      this translation unit.  */
   TREE_ADDRESSABLE (function) = 1;
--- gcc/testsuite/g++.dg/warn/deprecated-19.C.jj        2024-09-11 
12:50:25.342634444 +0200
+++ gcc/testsuite/g++.dg/warn/deprecated-19.C   2024-09-11 13:05:29.210222060 
+0200
@@ -0,0 +1,22 @@
+// PR c++/116636
+// { dg-do compile }
+// { dg-options "-pedantic -Wdeprecated" }
+
+struct A {
+  virtual int foo () = 0;
+};
+struct B : virtual A {
+  [[deprecated]] int foo () { return 0; }      // { dg-message "declared here" 
}
+};                                             // { dg-warning "C\\\+\\\+11 
attributes only available with" "" { target c++98_only } .-1 }
+struct C : virtual A {
+  [[gnu::unavailable]] int foo () { return 0; }        // { dg-message 
"declared here" }
+};                                             // { dg-warning "C\\\+\\\+11 
attributes only available with" "" { target c++98_only } .-1 }
+
+void
+bar ()
+{
+  B b;
+  b.foo ();                                    // { dg-warning "'virtual int 
B::foo\\\(\\\)' is deprecated" }
+  C c;
+  c.foo ();                                    // { dg-error "'virtual int 
C::foo\\\(\\\)' is unavailable" }
+}

        Jakub

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