[Bug target/104213] [12 Regression] bogus use-after-free in virtual dtor with -ffat-lto-objects on ARM

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104213

--- Comment #12 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Removing the COMPARISON_CLASS_P check regresses uninit-pr74762.C.  So how about

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 22d3dd1e2ad..6534a7fd320 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -17315,6 +17315,7 @@ finish_constructor_body (void)
       add_stmt (build_stmt (input_location, LABEL_EXPR, cdtor_label));

       val = DECL_ARGUMENTS (current_function_decl);
+      suppress_warning (val, OPT_Wuse_after_free);
       val = build2 (MODIFY_EXPR, TREE_TYPE (val),
            DECL_RESULT (current_function_decl), val);
       /* Return the address of the object.  */
@@ -17408,6 +17409,7 @@ finish_destructor_body (void)
       tree val;

       val = DECL_ARGUMENTS (current_function_decl);
+      suppress_warning (val, OPT_Wuse_after_free);
       val = build2 (MODIFY_EXPR, TREE_TYPE (val),
            DECL_RESULT (current_function_decl), val);
       /* Return the address of the object.  */
diff --git a/gcc/cp/optimize.cc b/gcc/cp/optimize.cc
index 4ad3f1dc9aa..13ab8b7361e 100644
--- a/gcc/cp/optimize.cc
+++ b/gcc/cp/optimize.cc
@@ -166,6 +166,7 @@ build_delete_destructor_body (tree delete_dtor, tree
complete_dtor)
   if (targetm.cxx.cdtor_returns_this ())
     {
       tree val = DECL_ARGUMENTS (delete_dtor);
+      suppress_warning (val, OPT_Wuse_after_free);
       val = build2 (MODIFY_EXPR, TREE_TYPE (val),
                     DECL_RESULT (delete_dtor), val);
       add_stmt (build_stmt (0, RETURN_EXPR, val));
diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index 8bc33eeb6fa..f39092ec416 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -3880,9 +3880,19 @@ pass_waccess::warn_invalid_pointer (tree ref, gimple
*use_stmt,
                    bool maybe, bool equality /* = false */)
 {
   /* Avoid printing the unhelpful "<unknown>" in the diagnostics.  */
-  if (ref && TREE_CODE (ref) == SSA_NAME
-      && (!SSA_NAME_VAR (ref) || DECL_ARTIFICIAL (SSA_NAME_VAR (ref))))
-    ref = NULL_TREE;
+  if (ref && TREE_CODE (ref) == SSA_NAME)
+    {
+      tree var = SSA_NAME_VAR (ref);
+      if (!var)
+   ref = NULL_TREE;
+      else if (DECL_ARTIFICIAL (var))
+   {
+     /* Don't warn for cases like when a cdtor returns 'this' on ARM.  */
+     if (warning_suppressed_p (var, OPT_Wuse_after_free))
+       return;
+     ref = NULL_TREE;
+   }
+    }

   location_t use_loc = gimple_location (use_stmt);
   if (use_loc == UNKNOWN_LOCATION)


I guess I can test & post it.