Trying to fix Mangler memory leak in TargetLoweringObjectFile.

Summary:
`TargetLoweringObjectFile` can be re-used and thus `TargetLoweringObjectFile::Initialize()`
can be called multiple times causing `Mang` pointer memory leak.

Reviewers: echristo

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D24659

llvm-svn: 281718

Author: Eric Liu

llvm/include/llvm/Target/TargetLoweringObjectFile.h

@@ -38,7 +38,7 @@ class TargetLoweringObjectFile : public MCObjectFileInfo {
   MCContext *Ctx;
 
   /// Name-mangler for global names.
-  Mangler *Mang;
+  Mangler *Mang = nullptr;
 
   TargetLoweringObjectFile(
     const TargetLoweringObjectFile&) = delete;

llvm/lib/Target/TargetLoweringObjectFile.cpp

@@ -43,6 +43,8 @@ using namespace llvm;
 void TargetLoweringObjectFile::Initialize(MCContext &ctx,
                                           const TargetMachine &TM) {
   Ctx = &ctx;
+  // `Initialize` can be called more than once.
+  if (Mang != nullptr) delete Mang;
   Mang = new Mangler();
   InitMCObjectFileInfo(TM.getTargetTriple(), TM.isPositionIndependent(),
                        TM.getCodeModel(), *Ctx);