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

non-trivial C union types

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: 365985

5 files changed, 110 insertions, 27 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 19cc1037c4c..8eeee4af0d3 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(
 
diff --git a/clang/test/PCH/non-trivial-c-union.m b/clang/test/PCH/non-trivial-c-union.m
new file mode 100644
index 00000000000..abd335497db
--- /dev/null
+++ b/clang/test/PCH/non-trivial-c-union.m
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -fblocks -fobjc-arc -fobjc-runtime-has-weak -emit-pch -o %t.pch %s
+// RUN: %clang_cc1 -fblocks -fobjc-arc -fobjc-runtime-has-weak -include-pch %t.pch -verify %s
+
+#ifndef HEADER
+#define HEADER
+
+typedef union {
+  id f0;
+} U0;
+
+#else
+
+// expected-note@-6 {{'U0' has subobjects that are non-trivial to destruct}}
+// expected-note@-7 {{'U0' has subobjects that are non-trivial to copy}}
+// expected-note@-8 {{'U0' has subobjects that are non-trivial to default-initialize}}
+// expected-note@-8 {{f0 has type '__strong id' that is non-trivial to destruct}}
+// expected-note@-9 {{f0 has type '__strong id' that is non-trivial to copy}}
+// expected-note@-10 {{f0 has type '__strong id' that is non-trivial to default-initialize}}
+
+U0 foo0(void); // expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to copy}}
+
+U0 g0; // expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+
+#endif
diff --git a/clang/test/SemaObjC/arc-decls.m b/clang/test/SemaObjC/arc-decls.m
index 0abd45dac33..28c3de99699 100644
--- a/clang/test/SemaObjC/arc-decls.m
+++ b/clang/test/SemaObjC/arc-decls.m
@@ -8,11 +8,7 @@ struct A {
 };
 
 union u {
-    id u; // expected-error {{ARC forbids Objective-C objects in union}}
-};
-
-union u_nontrivial_c {
-  struct A a; // expected-error {{non-trivial C types are disallowed in union}}
+  id u;
 };
 
 // Volatile fields are fine.
diff --git a/clang/test/SemaObjC/non-trivial-c-union.m b/clang/test/SemaObjC/non-trivial-c-union.m
new file mode 100644
index 00000000000..7bd82775451
--- /dev/null
+++ b/clang/test/SemaObjC/non-trivial-c-union.m
@@ -0,0 +1,82 @@
+// RUN: %clang_cc1 -fsyntax-only -fblocks -fobjc-arc -fobjc-runtime-has-weak -verify %s
+
+typedef union { // expected-note 12 {{'U0' has subobjects that are non-trivial to default-initialize}} expected-note 36 {{'U0' has subobjects that are non-trivial to destruct}} expected-note 28 {{'U0' has subobjects that are non-trivial to copy}}
+  id f0; // expected-note 12 {{f0 has type '__strong id' that is non-trivial to default-initialize}} expected-note 36 {{f0 has type '__strong id' that is non-trivial to destruct}} expected-note 28 {{f0 has type '__strong id' that is non-trivial to copy}}
+  __weak id f1; // expected-note 12 {{f1 has type '__weak id' that is non-trivial to default-initialize}} expected-note 36 {{f1 has type '__weak id' that is non-trivial to destruct}} expected-note 28 {{f1 has type '__weak id' that is non-trivial to copy}}
+} U0;
+
+typedef struct {
+  U0 f0;
+  id f1;
+} S0;
+
+id g0;
+U0 ug0; // expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+U0 ug1 = { .f0 = 0 };
+S0 sg0; // expected-error {{cannot default-initialize an object of type 'S0' since it contains a union that is non-trivial to default-initialize}}
+S0 sg1 = { .f0 = {0}, .f1 = 0 };
+S0 sg2 = { .f1 = 0 }; // expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+
+U0 foo0(U0); // expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to copy}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to copy}}
+S0 foo1(S0); // expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to copy}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to copy}}
+
+@interface C
+-(U0)m0:(U0)arg; // expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to copy}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to copy}}
+-(S0)m1:(S0)arg; // expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to copy}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to copy}}
+@end
+
+void testBlockFunction(void) {
+  (void)^(U0 a){ return ug0; }; // expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for a function/method parameter since it is a union that is non-trivial to copy}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to destruct}} expected-error {{cannot use type 'U0' for function/method return since it is a union that is non-trivial to copy}}
+  (void)^(S0 a){ return sg0; }; // expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for a function/method parameter since it contains a union that is non-trivial to copy}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to destruct}} expected-error {{cannot use type 'S0' for function/method return since it contains a union that is non-trivial to copy}}
+}
+void testAutoVar(void) {
+  U0 u0; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+  U0 u1 = ug0; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot copy-initialize an object of type 'U0' since it is a union that is non-trivial to copy}}
+  U0 u2 = { g0 }; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}}
+  U0 u3 = { .f1 = g0 }; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}}
+  S0 s0; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'S0' since it contains a union that is non-trivial to default-initialize}}
+  S0 s1 = sg0; // expected-error {{declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot copy-initialize an object of type 'S0' since it contains a union that is non-trivial to copy}}
+  S0 s2 = { ug0 }; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot copy-initialize an object of type 'U0' since it is a union that is non-trivial to copy}}
+  S0 s3 = { .f0 = ug0 }; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot copy-initialize an object of type 'U0' since it is a union that is non-trivial to copy}}
+  S0 s4 = { .f1 = g0 }; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+}
+
+void testAssignment(void) {
+  ug0 = ug1; // expected-error {{cannot assign to a variable of type 'U0' since it is a union that is non-trivial to copy}}
+  sg0 = sg1; // expected-error {{cannot assign to a variable of type 'S0' since it contains a union that is non-trivial to copy}}
+}
+
+U0 ug2 = (U0){ .f1 = 0 }; // expected-error {{cannot copy-initialize an object of type 'U0' since it is a union that is non-trivial to copy}}
+S0 sg3 = (S0){ .f0 = {0}, .f1 = 0 }; // expected-error {{cannot copy-initialize an object of type 'S0' since it contains a union that is non-trivial to copy}}
+S0 *sg4 = &(S0){ .f1 = 0 }; // expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+
+void testCompoundLiteral(void) {
+  const U0 *t0 = &(U0){ .f0 = g0 }; // expected-error {{cannot construct an automatic compound literal of type 'U0' since it is a union that is non-trivial to destruct}}
+  const U0 *t1 = &(U0){ .f1 = g0 }; // expected-error {{cannot construct an automatic compound literal of type 'U0' since it is a union that is non-trivial to destruct}}
+  const S0 *t2 = &(S0){ .f0 = ug0 }; // expected-error {{cannot construct an automatic compound literal of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot copy-initialize an object of type 'U0' since it is a union that is non-trivial to copy}}
+  const S0 *t3 = &(S0){ .f1 = g0 }; // expected-error {{cannot construct an automatic compound literal of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+}
+
+typedef void (^BlockTy)(void);
+void escapingFunc(BlockTy);
+void noescapingFunc(__attribute__((noescape)) BlockTy);
+
+void testBlockCapture(void) {
+  U0 t0; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+  S0 t1; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'S0' since it contains a union that is non-trivial to default-initialize}}
+  __block U0 t2; // expected-error {{cannot declare an automatic variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'U0' since it is a union that is non-trivial to default-initialize}}
+  __block S0 t3; // expected-error {{cannot declare an automatic variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot default-initialize an object of type 'S0' since it contains a union that is non-trivial to default-initialize}}
+
+  escapingFunc(^{ g0 = t0.f0; }); // expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to copy}}
+  escapingFunc(^{ g0 = t1.f0.f0; }); // expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to copy}}
+  escapingFunc(^{ g0 = t2.f0; }); // expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to copy}}
+  escapingFunc(^{ g0 = t3.f0.f0; }); // expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to copy}}
+  noescapingFunc(^{ g0 = t0.f0; }); // expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'U0' since it is a union that is non-trivial to copy}}
+  noescapingFunc(^{ g0 = t1.f0.f0; }); // expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to destruct}} expected-error {{cannot capture a variable of type 'S0' since it contains a union that is non-trivial to copy}}
+  noescapingFunc(^{ g0 = t2.f0; });
+  noescapingFunc(^{ g0 = t3.f0.f0; });
+}
+
+void testVolatileLValueToRValue(volatile U0 *a) {
+  (void)*a; // expected-error {{cannot use volatile type 'volatile U0' where it causes an lvalue-to-rvalue conversion since it is a union that is non-trivial to destruct}} // expected-error {{cannot use volatile type 'volatile U0' where it causes an lvalue-to-rvalue conversion since it is a union that is non-trivial to copy}}
+}