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[CodeGenObjCXX] Don't rematerialize default arguments of function

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parameters in the body of a block.

This fixes a bug where clang would materialize the default argument
inside the body of a block instead of passing the value via the block
descriptor.

For example, in the code below, foo1 would always print 42 regardless
of the value of argument "a" passed to foo1.

void foo1(const int a = 42 ) {
  auto block = ^{
    printf("%d\n", a);
  };
  block();
}

rdar://problem/24449235

llvm-svn: 268314
This commit is contained in:
Akira Hatanaka 2016-05-02 21:52:57 +00:00
parent 64f7a995b0
commit 3ba6535096
2 changed files with 21 additions and 0 deletions
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5
clang/lib/CodeGen/CGBlocks.cpp
View File

@ -262,6 +262,11 @@ static bool isSafeForCXXConstantCapture(QualType type) {
static llvm::Constant *tryCaptureAsConstant(CodeGenModule &CGM,
CodeGenFunction *CGF,
const VarDecl *var) {
// Don't rematerialize default arguments of function parameters.
if (auto *PD = dyn_cast<ParmVarDecl>(var))
if (PD->hasDefaultArg())
return nullptr;
QualType type = var->getType();
// We can only do this if the variable is const.

16
clang/test/CodeGenObjCXX/block-default-arg.mm Normal file
View File

@ -0,0 +1,16 @@
// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -emit-llvm -o - %s -std=c++11 -fblocks -fobjc-arc | FileCheck %s
// CHECK: define internal void @___Z16test_default_argi_block_invoke(i8* %[[BLOCK_DESCRIPTOR:.*]])
// CHECK: %[[BLOCK:.*]] = bitcast i8* %[[BLOCK_DESCRIPTOR]] to <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>*
// CHECK: %[[BLOCK_CAPTURE_ADDR:.*]] = getelementptr inbounds <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>, <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i32 }>* %[[BLOCK]], i32 0, i32 5
// CHECK: %[[V0:.*]] = load i32, i32* %[[BLOCK_CAPTURE_ADDR]]
// CHECK: call void @_Z4foo1i(i32 %[[V0]])
void foo1(int);
void test_default_arg(const int a = 42) {
auto block = ^{
foo1(a);
};
block();
}