Under a compiler flag, -freset-local-blocks,

wipe out stack blocks when they go out of scope.
// rdar://9227352


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134045 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 24 insertions, 0 deletions

diff --git a/lib/CodeGen/CGBlocks.cpp b/lib/CodeGen/CGBlocks.cpp
index a0a8d667df..20b5c9bed0 100644
--- a/lib/CodeGen/CGBlocks.cpp
+++ b/lib/CodeGen/CGBlocks.cpp
@@ -25,6 +25,22 @@
 using namespace clang;
 using namespace CodeGen;
 
+struct CallMemsetLocalBlockObject : EHScopeStack::Cleanup {
+  llvm::AllocaInst *BlockAddr;
+  CharUnits BlockSize;
+  
+  CallMemsetLocalBlockObject(llvm::AllocaInst *blockAddr, 
+                             CharUnits blocSize) 
+    : BlockAddr(blockAddr), BlockSize(blocSize) {}
+  
+  void Emit(CodeGenFunction &CGF, bool isForEH) {
+    CGF.Builder.CreateMemSet(BlockAddr, 
+                             llvm::ConstantInt::get(CGF.Int8Ty, 0xCD), 
+                             BlockSize.getQuantity(), 
+                             BlockAddr->getAlignment());
+  }
+};
+
 CGBlockInfo::CGBlockInfo(const BlockExpr *blockExpr, const char *N)
   : Name(N), CXXThisIndex(0), CanBeGlobal(false), NeedsCopyDispose(false),
     HasCXXObject(false), UsesStret(false), StructureType(0), Block(blockExpr) {
@@ -649,6 +665,9 @@ llvm::Value *CodeGenFunction::EmitBlockLiteral(const BlockExpr *blockExpr) {
   llvm::Value *result =
     Builder.CreateBitCast(blockAddr,
                           ConvertType(blockInfo.getBlockExpr()->getType()));
+  if (getLangOptions().ResetLocalBlocks)
+    EHStack.pushCleanup<CallMemsetLocalBlockObject>(NormalCleanup, blockAddr, 
+                                                    blockInfo.BlockSize);
 
   return result;
 }
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 41be873b35..d384c2b739 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1709,6 +1709,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
          !Args.hasArg(options::OPT_fno_blocks))) {
     CmdArgs.push_back("-fblocks");
   }
+  if (Args.hasArg(options::OPT_freset_local_blocks))
+    CmdArgs.push_back("-freset-local-blocks");
 
   // -faccess-control is default.
   if (Args.hasFlag(options::OPT_fno_access_control,
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 12e51a61e1..f2ca212b3a 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -638,6 +638,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-pthread");
   if (Opts.Blocks)
     Res.push_back("-fblocks");
+  if (Opts.ResetLocalBlocks)
+    Res.push_back("-freset-local-blocks");
   if (Opts.EmitAllDecls)
     Res.push_back("-femit-all-decls");
   if (Opts.MathErrno)
@@ -1612,6 +1614,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
 
   Opts.RTTI = !Args.hasArg(OPT_fno_rtti);
   Opts.Blocks = Args.hasArg(OPT_fblocks);
+  Opts.ResetLocalBlocks = Args.hasArg(OPT_freset_local_blocks);
   Opts.CharIsSigned = !Args.hasArg(OPT_fno_signed_char);
   Opts.ShortWChar = Args.hasArg(OPT_fshort_wchar);
   Opts.ShortEnums = Args.hasArg(OPT_fshort_enums);