From 1b71a22b28326b04bbdafcdb53c0a5f3917a11d8 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 26 Jul 2011 23:27:24 +0000
Subject: [PATCH] Re-fix r136172 so it isn't an error; apparently, some people
 are fond of their undefined behavior.

llvm-svn: 136183
---
 .../clang/Basic/DiagnosticSemaKinds.td        |  5 ++--
 clang/lib/Sema/SemaExprCXX.cpp                | 29 +++++++++----------
 clang/test/SemaCXX/new-delete.cpp             |  2 +-
 3 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 41aaebaa607e..7ee93568e335 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3421,8 +3421,9 @@ def warn_non_virtual_dtor : Warning<
 def warn_delete_non_virtual_dtor : Warning<
   "delete called on %0 that has virtual functions but non-virtual destructor">,
   InGroup<DeleteNonVirtualDtor>, DefaultIgnore;
-def err_delete_abstract_non_virtual_dtor : Error<
-  "cannot delete %0, which is abstract and does not have a virtual destructor">;
+def warn_delete_abstract_non_virtual_dtor : Warning<
+  "delete called on %0 that is abstract but has non-virtual destructor">,
+  InGroup<DeleteNonVirtualDtor>;
 def warn_overloaded_virtual : Warning<
   "%q0 hides overloaded virtual %select{function|functions}1">,
   InGroup<OverloadedVirtual>, DefaultIgnore;
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 86a4ecc1fc52..94a5bafa7c7d 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1913,18 +1913,6 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
           DiagnoseUseOfDecl(Dtor, StartLoc);
         }
 
-      // Deleting an abstract class with a non-virtual destructor is always
-      // undefined per [expr.delete]p3, and leads to strange-looking
-      // linker errors.
-      if (PointeeRD->isAbstract()) {
-        CXXDestructorDecl *dtor = PointeeRD->getDestructor();
-        if (dtor && !dtor->isVirtual()) {
-          Diag(StartLoc, diag::err_delete_abstract_non_virtual_dtor)
-              << PointeeElem;
-          return ExprError();
-        }
-      }
-
       // C++ [expr.delete]p3:
       //   In the first alternative (delete object), if the static type of the
       //   object to be deleted is different from its dynamic type, the static
@@ -1933,11 +1921,20 @@ Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
       //   behavior is undefined.
       //
       // Note: a final class cannot be derived from, no issue there
-      if (!ArrayForm && PointeeRD->isPolymorphic() &&
-          !PointeeRD->hasAttr<FinalAttr>()) {
+      if (PointeeRD->isPolymorphic() && !PointeeRD->hasAttr<FinalAttr>()) {
         CXXDestructorDecl *dtor = PointeeRD->getDestructor();
-        if (dtor && !dtor->isVirtual())
-          Diag(StartLoc, diag::warn_delete_non_virtual_dtor) << PointeeElem;
+        if (dtor && !dtor->isVirtual()) {
+          if (PointeeRD->isAbstract()) {
+            // If the class is abstract, we warn by default, because we're
+            // sure the code has undefined behavior.
+            Diag(StartLoc, diag::warn_delete_abstract_non_virtual_dtor)
+                << PointeeElem;
+          } else if (!ArrayForm) {
+            // Otherwise, if this is not an array delete, it's a bit suspect,
+            // but not necessarily wrong.
+            Diag(StartLoc, diag::warn_delete_non_virtual_dtor) << PointeeElem;
+          }
+        }
       }
 
     } else if (getLangOptions().ObjCAutoRefCount &&
diff --git a/clang/test/SemaCXX/new-delete.cpp b/clang/test/SemaCXX/new-delete.cpp
index 7545b7c136d1..748ce7770097 100644
--- a/clang/test/SemaCXX/new-delete.cpp
+++ b/clang/test/SemaCXX/new-delete.cpp
@@ -414,5 +414,5 @@ namespace PR10504 {
   struct A {
     virtual void foo() = 0;
   };
-  void f(A *x) { delete x; } // expected-error {{cannot delete 'PR10504::A', which is abstract and does not have a virtual destructor}}
+  void f(A *x) { delete x; } // expected-warning {{delete called on 'PR10504::A' that is abstract but has non-virtual destructor}}
 }