[Sema] Diagnose default-initialization, destruction, and copying of

non-trivial C union types

This recommits r365985, which was reverted because it broke a few
projects using unions containing non-trivial ObjC pointer fields in
system headers. We now have a patch to fix the problem (see
https://reviews.llvm.org/D65256).

Original commit message:

This patch diagnoses uses of non-trivial C unions and structs/unions
containing non-trivial C unions in the following contexts, which require
default-initialization, destruction, or copying of the union objects,
instead of disallowing fields of non-trivial types in C unions, which is
what we currently do:

- function parameters.
- function returns.
- assignments.
- compound literals.
- block captures except capturing of `__block` variables by non-escaping blocks.
- local and global variable definitions.
- lvalue-to-rvalue conversions of volatile types.

See the discussion in https://reviews.llvm.org/D62988 for more background.

rdar://problem/50679094

Differential Revision: https://reviews.llvm.org/D63753

llvm-svn: 371275

2 files changed, 3 insertions, 22 deletions

diff --git a/clang/test/CodeGenObjC/Inputs/strong_in_union.h b/clang/test/CodeGenObjC/Inputs/strong_in_union.h
deleted file mode 100644
index abe4549055c..00000000000
--- a/clang/test/CodeGenObjC/Inputs/strong_in_union.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#ifndef STRONG_IN_UNION_H
-#define STRONG_IN_UNION_H
-#pragma clang system_header
-
-typedef union {
-  id f0;
-  int *f1;
-} U;
-
-#endif // STRONG_IN_UNION_H
diff --git a/clang/test/CodeGenObjC/strong-in-c-struct.m b/clang/test/CodeGenObjC/strong-in-c-struct.m
index b3851772355..eae5013dd3f 100644
--- a/clang/test/CodeGenObjC/strong-in-c-struct.m
+++ b/clang/test/CodeGenObjC/strong-in-c-struct.m
@@ -1,11 +1,10 @@
-// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -emit-llvm -o - -DUSESTRUCT -I %S/Inputs %s | FileCheck %s
+// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -emit-llvm -o - -DUSESTRUCT %s | FileCheck %s
 
-// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -emit-pch -I %S/Inputs -o %t %s
-// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -include-pch %t -emit-llvm -o - -DUSESTRUCT -I %S/Inputs %s | FileCheck %s
+// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -emit-pch -o %t %s
+// RUN: %clang_cc1 -triple arm64-apple-ios11 -fobjc-arc -fblocks  -fobjc-runtime=ios-11.0 -include-pch %t -emit-llvm -o - -DUSESTRUCT %s | FileCheck %s
 
 #ifndef HEADER
 #define HEADER
-#include "strong_in_union.h"
 
 typedef void (^BlockTy)(void);
 
@@ -695,14 +694,6 @@ void test_copy_constructor_Bitfield1(Bitfield1 *a) {
   Bitfield1 t = *a;
 }
 
-// CHECK: define void @test_strong_in_union()
-// CHECK: alloca %{{.*}}
-// CHECK-NEXT: ret void
-
-void test_strong_in_union() {
-  U t;
-}
-
 // CHECK: define void @test_copy_constructor_VolatileArray(
 // CHECK: call void @__copy_constructor_8_8_s0_AB8s4n16_tv64w32_AE(