4 files changed, 15 insertions, 5 deletions
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 79425d4c21e..4d03bdb8ef4 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -891,8 +891,11 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
   } else if (FunctionDecl *UnsizedDealloc =
                  FD->getCorrespondingUnsizedGlobalDeallocationFunction()) {
     // Global sized deallocation functions get an implicit weak definition if
-    // they don't have an explicit definition.
+    // they don't have an explicit definition, if allowed.
+    assert(getLangOpts().DefaultSizedDelete &&
+           "Can't emit unallowed definition.");
     EmitSizedDeallocationFunction(*this, UnsizedDealloc);
+
   } else
     llvm_unreachable("no definition for emitted function");
 
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index bc52028a064..fdcbe2a42e8 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1615,13 +1615,13 @@ CodeGenModule::GetOrCreateLLVMFunction(StringRef MangledName,
       // don't need it anymore).
       addDeferredDeclToEmit(F, DDI->second);
       DeferredDecls.erase(DDI);
-
+      
       // Otherwise, if this is a sized deallocation function, emit a weak
-      // definition
-      // for it at the end of the translation unit.
+      // definition for it at the end of the translation unit.
     } else if (D && cast<FunctionDecl>(D)
                         ->getCorrespondingUnsizedGlobalDeallocationFunction()) {
-      addDeferredDeclToEmit(F, GD);
+      if (getLangOpts().DefaultSizedDelete)
+        addDeferredDeclToEmit(F, GD);
 
       // Otherwise, there are cases we have to worry about where we're
       // using a declaration for which we must emit a definition but where
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 0f74ea176ca..fafd2145fcd 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -4243,6 +4243,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (!Args.hasFlag(options::OPT_fassume_sane_operator_new,
                     options::OPT_fno_assume_sane_operator_new))
     CmdArgs.push_back("-fno-assume-sane-operator-new");
+  
+  // -def-sized-delete: default implementation of sized delete as a
+  // weak definition.
+  if (Args.hasArg(options::OPT_fdef_sized_delete))
+    CmdArgs.push_back("-fdef-sized-delete");
 
   // -fconstant-cfstrings is default, and may be subject to argument translation
   // on Darwin.
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index ee671681b48..b060712f672 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1525,6 +1525,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.SizedDeallocation |= Args.hasArg(OPT_fsized_deallocation);
+  Opts.DefaultSizedDelete = Opts.SizedDeallocation &&
+      Args.hasArg(OPT_fdef_sized_delete);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);
   Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);
   Opts.ElideConstructors = !Args.hasArg(OPT_fno_elide_constructors);