erik.pilkington updated this revision to Diff 179964.
erik.pilkington marked 10 inline comments as done.
erik.pilkington added a comment.
Address review comments. Also, make the attribute apply to parameters via the
function declaration instead to parameters directly. i.e.:
__attribute__((objc_externally_retained(1)))
void foo(Widget *w) { ... }
The rule being that when this is applied to a non-param variable, it behaves as
before, but when applied to a function it takes zero or more indices that
correspond to which parameters are pseudo-strong. If no indices are specified,
then it applies to every parameter that isn't explicitly __strong. This has a
couple of advantages:
1. It fixes a more "theoretical" ABI break when used with objective-c++
decltype:
void foo(Widget *w, decltype(w) *) {}
Previously, adding an attribute to `w` would have caused the mangling of `foo`
to change because `decltype(w)` was `Widget * __strong const`. Now, we wait
until the `FunctionType` is constructed and the `decltype(w)` is resolved
before tampering with the parameter type, so this gets the same mangling, but
we still get the extra safety.
2. It makes it more obvious what this attribute can/can't be applied to. i.e.
it now is impossible to annotate parameters of function types, which doesn't
make any sense.
3. We don't have to add special-case hacks to `#pragma clang attribute` to make
this work. i.e.:
#pragma clang attribute push (__attribute__((objc_externally_retained)),
apply_to=any(function,objc_method,block))
void f(Widget *w, __strong Widget *other) {} // w is externally-retained,
other is not
#pragma clang attribute pop
Whereas previously we would have had to add something like
`apply_to=is_objc_retainable_pointer_parameter_of_function_definition_that_is_implicitly_strong`
in order to get these semantics.
Thanks for taking a look!
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D55865/new/
https://reviews.llvm.org/D55865
Files:
clang/docs/AutomaticReferenceCounting.rst
clang/include/clang/AST/Decl.h
clang/include/clang/AST/DeclObjC.h
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/CodeGen/CGDecl.cpp
clang/lib/CodeGen/CGExpr.cpp
clang/lib/Sema/SemaDeclAttr.cpp
clang/lib/Sema/SemaExpr.cpp
clang/lib/Serialization/ASTReaderDecl.cpp
clang/lib/Serialization/ASTWriterDecl.cpp
clang/test/CodeGenObjC/externally-retained.m
clang/test/Misc/pragma-attribute-supported-attributes-list.test
clang/test/SemaObjC/externally-retained-no-arc.m
clang/test/SemaObjC/externally-retained.m
Index: clang/test/SemaObjC/externally-retained.m
===================================================================
--- /dev/null
+++ clang/test/SemaObjC/externally-retained.m
@@ -0,0 +1,127 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.13.0 -fobjc-runtime=macosx-10.13.0 -fblocks -fobjc-arc %s -verify
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.13.0 -fobjc-runtime=macosx-10.13.0 -fblocks -fobjc-arc -xobjective-c++ %s -verify
+
+#define EXT_RET __attribute__((objc_externally_retained))
+#define CALL_RET(...) __attribute__((objc_externally_retained(__VA_ARGS__)))
+
+@interface ObjCTy
+@end
+
+void test1() {
+ EXT_RET int a; // expected-warning{{'objc_externally_retained' can only be applied to}}
+ EXT_RET __weak ObjCTy *b; // expected-warning{{'objc_externally_retained' can only be applied to}}
+ EXT_RET __weak int (^c)(); // expected-warning{{'objc_externally_retained' can only be applied to}}
+
+ EXT_RET int (^d)() = ^{return 0;};
+ EXT_RET ObjCTy *e = 0;
+ EXT_RET __strong ObjCTy *f = 0;
+
+ e = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ f = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ d = ^{ return 0; }; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+}
+
+void test2(ObjCTy *a);
+
+void test2(ObjCTy *a) CALL_RET(1) {
+ a = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+}
+
+EXT_RET ObjCTy *test3; // expected-warning{{'objc_externally_retained' can only be applied to}}
+
+@interface X // expected-warning{{defined without specifying a base class}} expected-note{{add a super class}}
+-(void)m: (ObjCTy *) p;
+@end
+@implementation X
+-(void)m: (ObjCTy *) p CALL_RET(1) {
+ p = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+}
+@end
+
+void test4() {
+ __attribute__((objc_externally_retained(0))) ObjCTy *a; // expected-error{{'objc_externally_retained' attribute takes no arguments}}
+}
+
+void test5(ObjCTy *first, __strong ObjCTy *second) CALL_RET() {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0; // fine
+}
+
+void test6(ObjCTy *first,
+ ObjCTy *second,
+ __strong ObjCTy *third) CALL_RET(1, 3) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+ third = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+}
+
+__attribute__((objc_root_class)) @interface Y @end
+
+@implementation Y
+- (void)test7:(ObjCTy *)first
+ withSecond:(ObjCTy *)second
+ withThird:(ObjCTy *)third
+ CALL_RET(1, 2) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ third = 0;
+}
+@end
+
+void (^blk)() = ^CALL_RET(1) {}; // expected-error{{'objc_externally_retained' attribute parameter 1 is out of bounds}}
+void (^blk2)(ObjCTy *, ObjCTy *, ObjCTy *) = ^(ObjCTy *first, ObjCTy *second,
+ ObjCTy *third) CALL_RET(2, 3) {
+ first = 0;
+ second = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ third = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+};
+
+CALL_RET(1) void test7(__strong ObjCTy *first, ObjCTy *second) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+}
+
+void test8(EXT_RET ObjCTy *x) {} // expected-warning{{'objc_externally_retained' attribute only applies to variables}}
+
+#pragma clang attribute ext_ret.push(__attribute__((objc_externally_retained)), apply_to=any(function, block, objc_method))
+void test9(ObjCTy *first, __strong ObjCTy *second) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+}
+void (^test10)(ObjCTy *first, ObjCTy *second) = ^(ObjCTy *first, __strong ObjCTy *second) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+};
+__attribute__((objc_root_class)) @interface Test11 @end
+@implementation Test11
+-(void)meth: (ObjCTy *)first withSecond:(__strong ObjCTy *)second {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+}
++(void)othermeth: (ObjCTy *)first withSecond:(__strong ObjCTy *)second {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+}
+@end
+
+#if __cplusplus
+class Test12 {
+ void inline_member(ObjCTy *first, __strong ObjCTy *second) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+ }
+ static void static_inline_member(ObjCTy *first, __strong ObjCTy *second) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+ }
+};
+#endif
+
+void test13(ObjCTy *first, __weak ObjCTy *second, __unsafe_unretained ObjCTy *third, __strong ObjCTy *fourth) {
+ first = 0; // expected-error{{variable declared with 'objc_externally_retained' cannot be modified in ARC}}
+ second = 0;
+ third = 0;
+ fourth = 0;
+}
+
+#pragma clang attribute ext_ret.pop
Index: clang/test/SemaObjC/externally-retained-no-arc.m
===================================================================
--- /dev/null
+++ clang/test/SemaObjC/externally-retained-no-arc.m
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 %s -verify
+
+@interface NSWidget @end
+
+__attribute__((objc_externally_retained(1))) void f(NSWidget *p) { // expected-warning{{'objc_externally_retained' attribute ignored}}
+ __attribute__((objc_externally_retained)) NSWidget *w; // expected-warning{{'objc_externally_retained' attribute ignored}}
+}
Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===================================================================
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -94,6 +94,7 @@
// CHECK-NEXT: ObjCBridgeRelated (SubjectMatchRule_record)
// CHECK-NEXT: ObjCException (SubjectMatchRule_objc_interface)
// CHECK-NEXT: ObjCExplicitProtocolImpl (SubjectMatchRule_objc_protocol)
+// CHECK-NEXT: ObjCExternallyRetained (SubjectMatchRule_variable_not_is_parameter, SubjectMatchRule_function, SubjectMatchRule_block, SubjectMatchRule_objc_method)
// CHECK-NEXT: ObjCMethodFamily (SubjectMatchRule_objc_method)
// CHECK-NEXT: ObjCPreciseLifetime (SubjectMatchRule_variable)
// CHECK-NEXT: ObjCRequiresPropertyDefs (SubjectMatchRule_objc_interface)
Index: clang/test/CodeGenObjC/externally-retained.m
===================================================================
--- /dev/null
+++ clang/test/CodeGenObjC/externally-retained.m
@@ -0,0 +1,125 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.13.0 -fobjc-arc -fblocks -Wno-objc-root-class -O0 %s -S -emit-llvm -o - | FileCheck %s --dump-input-on-failure
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.13.0 -fobjc-arc -fblocks -Wno-objc-root-class -O0 -xobjective-c++ -std=c++11 %s -S -emit-llvm -o - | FileCheck %s --check-prefix CHECKXX --dump-input-on-failure
+
+#define EXT_RET __attribute__((objc_externally_retained))
+#define CALL_RET(...) __attribute__((objc_externally_retained(__VA_ARGS__)))
+
+@interface ObjTy @end
+
+ObjTy *global;
+
+#if __cplusplus
+// Suppress name mangling in C++ mode for the sake of check lines.
+extern "C" void param(ObjTy *p);
+extern "C" void local();
+extern "C" void in_init();
+extern "C" void anchor();
+extern "C" void block_capture(ObjTy *);
+extern "C" void esc(void (^)());
+extern "C" void escp(void (^)(ObjTy *));
+extern "C" void block_param();
+#endif
+
+void param(ObjTy *p) CALL_RET(1) {
+ // CHECK-LABEL: define void @param
+ // CHECK-NOT: llvm.objc.
+ // CHECK ret
+}
+
+void local() {
+ EXT_RET ObjTy *local = global;
+ // CHECK-LABEL: define void @local
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+
+void in_init() {
+ // Test that we do the right thing when a variable appears in it's own
+ // initializer. Here, we release the value stored in 'wat' after overwriting
+ // it, in case it was somehow set to point to a non-null object while it's
+ // initializer is being evaluated.
+ EXT_RET ObjTy *wat = 0 ? wat : global;
+
+ // CHECK-LABEL: define void @in_init
+ // CHECK: [[WAT:%.*]] = alloca
+ // CHECK-NEXT: store {{.*}} null, {{.*}} [[WAT]]
+ // CHECK-NEXT: [[GLOBAL:%.*]] = load {{.*}} @global
+ // CHECK-NEXT: [[WAT_LOAD:%.*]] = load {{.*}} [[WAT]]
+ // CHECK-NEXT: store {{.*}} [[GLOBAL]], {{.*}} [[WAT]]
+ // CHECK-NEXT: [[CASTED:%.*]] = bitcast {{.*}} [[WAT_LOAD]] to
+ // CHECK-NEXT: call void @llvm.objc.release(i8* [[CASTED]])
+
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+
+void esc(void (^)());
+
+void block_capture(ObjTy *obj) CALL_RET(1) {
+ esc(^{ (void)obj; });
+
+ // CHECK-LABEL: define void @block_capture
+ // CHECK-NOT: llvm.objc.
+ // CHECK: call i8* @llvm.objc.retain
+ // CHECK-NOT: llvm.objc.
+ // CHECK: call void @esc
+ // CHECK-NOT: llvm.objc.
+ // CHECK: call void @llvm.objc.storeStrong({{.*}} null)
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+
+ // CHECK-LABEL: define {{.*}} void @__copy_helper_block_
+ // CHECK-NOT: llvm.objc.
+ // CHECK: llvm.objc.storeStrong
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+
+ // CHECK-LABEL: define {{.*}} void @__destroy_helper_block_
+ // CHECK-NOT: llvm.objc.
+ // CHECK: llvm.objc.storeStrong({{.*}} null)
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+
+void escp(void (^)(ObjTy *));
+
+void block_param() {
+ escp(^(ObjTy *p) CALL_RET(1) {});
+
+ // CHECK-LABEL: define internal void @__block_param_block_invoke
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+
+@interface Inter
+-(void)m1: (ObjTy *)w;
+@end
+
+@implementation Inter
+-(void)m1: (ObjTy *) w CALL_RET(1) {
+ // CHECK-LABEL: define internal void @"\01-[Inter m1:]"
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+-(void)m2: (__strong ObjTy *) w CALL_RET(1) {
+ // CHECK-LABEL: define internal void @"\01-[Inter m2:]"
+ // CHECK-NOT: llvm.objc.
+ // CHECK: ret
+}
+@end
+
+#if __cplusplus
+// Verify that the implicit "const" doesn't make it into the name mangling in
+// C++ mode.
+int takes_p(ObjTy *p);
+int call_it = takes_p(0);
+int takes_p(EXT_RET ObjTy *p) {
+ return 0;
+}
+// CHECKXX: _Z7takes_pP5ObjTy
+
+// Verify that the decltype(p) is resolved before 'p' is made implicitly const.
+__attribute__((objc_externally_retained(1))) void foo(ObjTy *p, decltype(p)) {}
+// CHECKXX: _Z3fooP5ObjTyS0_
+
+#endif
Index: clang/lib/Serialization/ASTWriterDecl.cpp
===================================================================
--- clang/lib/Serialization/ASTWriterDecl.cpp
+++ clang/lib/Serialization/ASTWriterDecl.cpp
@@ -922,13 +922,13 @@
Record.push_back(D->getStorageClass());
Record.push_back(D->getTSCSpec());
Record.push_back(D->getInitStyle());
+ Record.push_back(D->isARCPseudoStrong());
if (!isa<ParmVarDecl>(D)) {
Record.push_back(D->isThisDeclarationADemotedDefinition());
Record.push_back(D->isExceptionVariable());
Record.push_back(D->isNRVOVariable());
Record.push_back(D->isCXXForRangeDecl());
Record.push_back(D->isObjCForDecl());
- Record.push_back(D->isARCPseudoStrong());
Record.push_back(D->isInline());
Record.push_back(D->isInlineSpecified());
Record.push_back(D->isConstexpr());
@@ -1986,6 +1986,7 @@
Abv->Add(BitCodeAbbrevOp(0)); // SClass
Abv->Add(BitCodeAbbrevOp(0)); // TSCSpec
Abv->Add(BitCodeAbbrevOp(0)); // InitStyle
+ Abv->Add(BitCodeAbbrevOp(0)); // ARCPseudoStrong
Abv->Add(BitCodeAbbrevOp(0)); // Linkage
Abv->Add(BitCodeAbbrevOp(0)); // HasInit
Abv->Add(BitCodeAbbrevOp(0)); // HasMemberSpecializationInfo
@@ -2062,12 +2063,12 @@
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // SClass
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // TSCSpec
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // InitStyle
+ Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isARCPseudoStrong
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsThisDeclarationADemotedDefinition
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isExceptionVariable
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isNRVOVariable
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isCXXForRangeDecl
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isObjCForDecl
- Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isARCPseudoStrong
Abv->Add(BitCodeAbbrevOp(0)); // isInline
Abv->Add(BitCodeAbbrevOp(0)); // isInlineSpecified
Abv->Add(BitCodeAbbrevOp(0)); // isConstexpr
Index: clang/lib/Serialization/ASTReaderDecl.cpp
===================================================================
--- clang/lib/Serialization/ASTReaderDecl.cpp
+++ clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1350,6 +1350,7 @@
VD->VarDeclBits.SClass = (StorageClass)Record.readInt();
VD->VarDeclBits.TSCSpec = Record.readInt();
VD->VarDeclBits.InitStyle = Record.readInt();
+ VD->VarDeclBits.ARCPseudoStrong = Record.readInt();
if (!isa<ParmVarDecl>(VD)) {
VD->NonParmVarDeclBits.IsThisDeclarationADemotedDefinition =
Record.readInt();
@@ -1357,7 +1358,6 @@
VD->NonParmVarDeclBits.NRVOVariable = Record.readInt();
VD->NonParmVarDeclBits.CXXForRangeDecl = Record.readInt();
VD->NonParmVarDeclBits.ObjCForDecl = Record.readInt();
- VD->NonParmVarDeclBits.ARCPseudoStrong = Record.readInt();
VD->NonParmVarDeclBits.IsInline = Record.readInt();
VD->NonParmVarDeclBits.IsInlineSpecified = Record.readInt();
VD->NonParmVarDeclBits.IsConstexpr = Record.readInt();
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -11223,17 +11223,23 @@
if (var->isARCPseudoStrong() &&
(!var->getTypeSourceInfo() ||
!var->getTypeSourceInfo()->getType().isConstQualified())) {
- // There are two pseudo-strong cases:
+ // There are three pseudo-strong cases:
// - self
ObjCMethodDecl *method = S.getCurMethodDecl();
- if (method && var == method->getSelfDecl())
+ if (method && var == method->getSelfDecl()) {
DiagID = method->isClassMethod()
? diag::err_typecheck_arc_assign_self_class_method
: diag::err_typecheck_arc_assign_self;
+ // - Objective-C externally_retained attribute.
+ } else if (var->hasAttr<ObjCExternallyRetainedAttr>() ||
+ isa<ParmVarDecl>(var)) {
+ DiagID = diag::err_typecheck_arc_assign_externally_retained;
+
// - fast enumeration variables
- else
+ } else {
DiagID = diag::err_typecheck_arr_assign_enumeration;
+ }
SourceRange Assign;
if (Loc != OrigLoc)
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -93,6 +93,17 @@
return cast<ObjCMethodDecl>(D)->param_size();
}
+static const ParmVarDecl *getFunctionOrMethodParam(const Decl *D,
+ unsigned Idx) {
+ if (const auto *FD = dyn_cast<FunctionDecl>(D))
+ return FD->getParamDecl(Idx);
+ if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
+ return MD->getParamDecl(Idx);
+ if (const auto *BD = dyn_cast<BlockDecl>(D))
+ return BD->getParamDecl(Idx);
+ return nullptr;
+}
+
static QualType getFunctionOrMethodParamType(const Decl *D, unsigned Idx) {
if (const FunctionType *FnTy = D->getFunctionType())
return cast<FunctionProtoType>(FnTy)->getParamType(Idx);
@@ -103,12 +114,8 @@
}
static SourceRange getFunctionOrMethodParamRange(const Decl *D, unsigned Idx) {
- if (const auto *FD = dyn_cast<FunctionDecl>(D))
- return FD->getParamDecl(Idx)->getSourceRange();
- if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
- return MD->parameters()[Idx]->getSourceRange();
- if (const auto *BD = dyn_cast<BlockDecl>(D))
- return BD->getParamDecl(Idx)->getSourceRange();
+ if (auto *PVD = getFunctionOrMethodParam(D, Idx))
+ return PVD->getSourceRange();
return SourceRange();
}
@@ -6093,6 +6100,103 @@
UninitializedAttr(AL.getLoc(), S.Context, Index));
}
+static bool tryMakeVariablePseudoStrong(Sema &S, VarDecl *VD,
+ bool DiagnoseFailure) {
+ QualType Ty = VD->getType();
+ if (!Ty->isObjCRetainableType()) {
+ if (DiagnoseFailure) {
+ S.Diag(VD->getBeginLoc(), diag::warn_ignored_objc_externally_retained)
+ << 0;
+ }
+ return false;
+ }
+
+ Qualifiers::ObjCLifetime LifetimeQual = Ty.getQualifiers().getObjCLifetime();
+
+ // Sema::inferObjCARCLifetime must run after processing decl attributes
+ // (because __block lowers to an attribute), so if the lifetime hasn't been
+ // explicitly specified, infer it locally now.
+ if (LifetimeQual == Qualifiers::OCL_None)
+ LifetimeQual = Ty->getObjCARCImplicitLifetime();
+
+ // The attributes only really makes sense for __strong variables; ignore any
+ // attempts to annotate a parameter with any other lifetime qualifier.
+ if (LifetimeQual != Qualifiers::OCL_Strong) {
+ if (DiagnoseFailure) {
+ S.Diag(VD->getBeginLoc(), diag::warn_ignored_objc_externally_retained)
+ << 1;
+ }
+ return false;
+ }
+
+ // Tampering with the type of a VarDecl here is a bit of a hack, but we need
+ // to ensure that the variable is 'const' so that we can error on
+ // modification, which can otherwise over-release.
+ VD->setType(Ty.withConst());
+ VD->setARCPseudoStrong(true);
+ return true;
+}
+
+static void handleObjCExternallyRetainedAttr(Sema &S, Decl *D,
+ const ParsedAttr &AL) {
+ if (auto *VD = dyn_cast<VarDecl>(D)) {
+ assert(!isa<ParmVarDecl>(VD) && "should be diagnosed automatically");
+ if (AL.getNumArgs() > 0) {
+ S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments)
+ << AL << 0;
+ return;
+ }
+
+ if (!VD->hasLocalStorage()) {
+ S.Diag(D->getBeginLoc(), diag::warn_ignored_objc_externally_retained)
+ << 0 << 0;
+ return;
+ }
+
+ if (!tryMakeVariablePseudoStrong(S, VD, /*DiagnoseFailure=*/true))
+ return;
+
+ handleSimpleAttribute<ObjCExternallyRetainedAttr>(S, D, AL);
+ return;
+ }
+
+ // If D is a function-like declaration (method, block, or function), and no
+ // index arguments were used, then we make every parameter psuedo-strong.
+ if (AL.getNumArgs() == 0) {
+ for (unsigned I = 0, E = getFunctionOrMethodNumParams(D); I != E; ++I) {
+ auto *PVD = const_cast<ParmVarDecl *>(getFunctionOrMethodParam(D, I));
+ QualType Ty = PVD->getType();
+
+ // If a user wrote a parameter with __strong explicitly, then assume they
+ // want "real" strong semantics for that parameter. This works because if
+ // the parameter was written with __strong, then the strong qualifier will
+ // be non-local.
+ if (Ty.getLocalUnqualifiedType().getQualifiers().getObjCLifetime() ==
+ Qualifiers::OCL_Strong)
+ continue;
+
+ tryMakeVariablePseudoStrong(S, PVD, /*DiagnoseFailure=*/false);
+ }
+ handleSimpleAttribute<ObjCExternallyRetainedAttr>(S, D, AL);
+ return;
+ }
+
+ // Otherwise, walk through the parameters that correspond to the attribute's
+ // arguments, marking them pseudo-strong.
+ for (size_t I = 0, E = AL.getNumArgs(); I != E; ++I) {
+ Expr *AsExpr = AL.getArgAsExpr(I);
+ ParamIdx Idx;
+ if (!checkFunctionOrMethodParameterIndex(S, D, AL, I + 1, AsExpr, Idx))
+ return;
+
+ auto *PVD = const_cast<ParmVarDecl *>(
+ getFunctionOrMethodParam(D, Idx.getASTIndex()));
+ tryMakeVariablePseudoStrong(S, PVD, /*DiagnoseFailure=*/true);
+ }
+
+ handleSimpleAttribute<ObjCExternallyRetainedAttr>(S, D, AL);
+}
+
//===----------------------------------------------------------------------===//
// Top Level Sema Entry Points
//===----------------------------------------------------------------------===//
@@ -6788,6 +6892,10 @@
case ParsedAttr::AT_Uninitialized:
handleUninitializedAttr(S, D, AL);
break;
+
+ case ParsedAttr::AT_ObjCExternallyRetained:
+ handleObjCExternallyRetainedAttr(S, D, AL);
+ break;
}
}
Index: clang/lib/CodeGen/CGExpr.cpp
===================================================================
--- clang/lib/CodeGen/CGExpr.cpp
+++ clang/lib/CodeGen/CGExpr.cpp
@@ -419,8 +419,12 @@
EmitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *M) {
const Expr *E = M->GetTemporaryExpr();
- // FIXME: ideally this would use EmitAnyExprToMem, however, we cannot do so
- // as that will cause the lifetime adjustment to be lost for ARC
+ assert((!M->getExtendingDecl() || !isa<VarDecl>(M->getExtendingDecl()) ||
+ !cast<VarDecl>(M->getExtendingDecl())->isARCPseudoStrong()) &&
+ "Reference should never be pseudo-strong!");
+
+ // FIXME: ideally this would use EmitAnyExprToMem, however, we cannot do so
+ // as that will cause the lifetime adjustment to be lost for ARC
auto ownership = M->getType().getObjCLifetime();
if (ownership != Qualifiers::OCL_None &&
ownership != Qualifiers::OCL_ExplicitNone) {
Index: clang/lib/CodeGen/CGDecl.cpp
===================================================================
--- clang/lib/CodeGen/CGDecl.cpp
+++ clang/lib/CodeGen/CGDecl.cpp
@@ -797,15 +797,21 @@
case Qualifiers::OCL_None:
llvm_unreachable("present but none");
+ case Qualifiers::OCL_Strong: {
+ if (!D || !isa<VarDecl>(D) || !cast<VarDecl>(D)->isARCPseudoStrong()) {
+ value = EmitARCRetainScalarExpr(init);
+ break;
+ }
+ // If D is pseudo-strong, treat it like __unsafe_unretained here. This means
+ // that we omit the retain, and causes non-autoreleased return values to be
+ // immediately released.
+ LLVM_FALLTHROUGH;
+ }
+
case Qualifiers::OCL_ExplicitNone:
value = EmitARCUnsafeUnretainedScalarExpr(init);
break;
- case Qualifiers::OCL_Strong: {
- value = EmitARCRetainScalarExpr(init);
- break;
- }
-
case Qualifiers::OCL_Weak: {
// If it's not accessed by the initializer, try to emit the
// initialization with a copy or move.
@@ -2324,15 +2330,11 @@
// cleanup to do the release at the end of the function.
bool isConsumed = D.hasAttr<NSConsumedAttr>();
- // 'self' is always formally __strong, but if this is not an
- // init method then we don't want to retain it.
+ // If a parameter is pseudo-strong then we can omit the implicit retain.
if (D.isARCPseudoStrong()) {
- const ObjCMethodDecl *method = cast<ObjCMethodDecl>(CurCodeDecl);
- assert(&D == method->getSelfDecl());
- assert(lt == Qualifiers::OCL_Strong);
- assert(qs.hasConst());
- assert(method->getMethodFamily() != OMF_init);
- (void) method;
+ assert(lt == Qualifiers::OCL_Strong &&
+ "pseudo-strong variable isn't strong?");
+ assert(qs.hasConst() && "pseudo-strong variable should be const!");
lt = Qualifiers::OCL_ExplicitNone;
}
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3489,6 +3489,12 @@
def err_objc_attr_protocol_requires_definition : Error<
"attribute %0 can only be applied to @protocol definitions, not forward declarations">;
+def warn_ignored_objc_externally_retained : Warning<
+ "'objc_externally_retained' can only be applied to local variables or "
+ "functions with parameters "
+ "%select{of retainable type|with strong ownership}0">,
+ InGroup<IgnoredAttributes>;
+
// Function Parameter Semantic Analysis.
def err_param_with_void_type : Error<"argument may not have 'void' type">;
def err_void_only_param : Error<
@@ -5262,6 +5268,9 @@
def err_typecheck_arr_assign_enumeration : Error<
"fast enumeration variables cannot be modified in ARC by default; "
"declare the variable __strong to allow this">;
+def err_typecheck_arc_assign_externally_retained : Error<
+ "variable declared with 'objc_externally_retained' "
+ "cannot be modified in ARC">;
def warn_arc_retained_assign : Warning<
"assigning retained object to %select{weak|unsafe_unretained}0 "
"%select{property|variable}1"
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -3774,3 +3774,47 @@
(even after inlining) end up hardened.
}];
}
+
+def ObjCExternallyRetainedDocs : Documentation {
+ let Category = DocCatVariable;
+ let Content = [{
+The ``objc_externally_retained`` attribute can be applied to strong parameters
+via functions (or blocks or methods) or directly to local variables in ARC mode.
+When applied to parameters, it causes clang to omit the implicit calls to
+``objc_retain`` and ``objc_release`` on a parameter on function entry and exit
+respectively. When applied to local variables, it causes clang to omit the call
+to ``objc_retain`` on variable initialization, and ``objc_release`` when the
+variable goes out of scope. Parameters and variables annotated with this
+attribute are implicitly ``const``. For instance:
+
+.. code-block: objc
+
+ @class WobbleAmount;
+
+ @interface Widget : NSObject
+ -(void)wobble:(WobbleAmount *)amount;
+ @end
+
+ @implementation Widget
+ -(void)wobble:(WobbleAmount *)amount
+ __attribute__((objc_externally_retained(1))) {
+ // 'amount' and 'alias' aren't retained on entry, nor released on exit.
+ __attribute__((objc_externally_retained)) WobbleAmount *alias = amount;
+ }
+ @end
+
+Unlike an ``__unsafe_unretained`` variable, an externally-retained variable
+remains semantically ``__strong``. This affects features like block capture
+which copy the current value of the variable into a capture field of the same
+type: the block's capture field will still be ``__strong``, and so the value
+will be retained as part of capturing it and released when the block is
+destroyed. It also affects C++ features such as lambda capture, ``decltype``,
+and template argument deduction.
+
+This attribute is meant to be used to opt out of the additional safety that ARC
+provides when the programmer knows that the safety isn't necessary. You can read
+more about ARC `here
+<https://clang.llvm.org/docs/AutomaticReferenceCounting.html>`_.
+
+ }];
+}
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -300,6 +300,7 @@
def RenderScript : LangOpt<"RenderScript">;
def ObjC : LangOpt<"ObjC">;
def BlocksSupported : LangOpt<"Blocks">;
+def ObjCAutoRefCount : LangOpt<"ObjCAutoRefCount">;
// Defines targets for target-specific attributes. Empty lists are unchecked.
class TargetSpec {
@@ -3137,3 +3138,11 @@
let Subjects = SubjectList<[LocalVar]>;
let Documentation = [UninitializedDocs];
}
+
+def ObjCExternallyRetained : InheritableAttr {
+ let LangOpts = [ObjCAutoRefCount];
+ let Spellings = [Clang<"objc_externally_retained">];
+ let Args = [VariadicParamIdxArgument<"Args">];
+ let Subjects = SubjectList<[NonParmVar, Function, Block, ObjCMethod]>;
+ let Documentation = [ObjCExternallyRetainedDocs];
+}
Index: clang/include/clang/AST/DeclObjC.h
===================================================================
--- clang/include/clang/AST/DeclObjC.h
+++ clang/include/clang/AST/DeclObjC.h
@@ -369,6 +369,14 @@
NumParams);
}
+ ParmVarDecl *getParamDecl(unsigned Idx) {
+ assert(Idx < NumParams && "Index out of bounds!");
+ return getParams()[Idx];
+ }
+ const ParmVarDecl *getParamDecl(unsigned Idx) const {
+ return const_cast<ObjCMethodDecl *>(this)->getParamDecl(Idx);
+ }
+
/// Sets the method's parameters and selector source locations.
/// If the method is implicit (not coming from source) \p SelLocs is
/// ignored.
Index: clang/include/clang/AST/Decl.h
===================================================================
--- clang/include/clang/AST/Decl.h
+++ clang/include/clang/AST/Decl.h
@@ -866,8 +866,12 @@
unsigned SClass : 3;
unsigned TSCSpec : 2;
unsigned InitStyle : 2;
+
+ /// Whether this variable is an ARC pseudo-__strong variable; see
+ /// isARCPseudoStrong() for details.
+ unsigned ARCPseudoStrong : 1;
};
- enum { NumVarDeclBits = 7 };
+ enum { NumVarDeclBits = 8 };
protected:
enum { NumParameterIndexBits = 8 };
@@ -940,10 +944,6 @@
/// Whether this variable is the for-in loop declaration in Objective-C.
unsigned ObjCForDecl : 1;
- /// Whether this variable is an ARC pseudo-__strong
- /// variable; see isARCPseudoStrong() for details.
- unsigned ARCPseudoStrong : 1;
-
/// Whether this variable is (C++1z) inline.
unsigned IsInline : 1;
@@ -1349,17 +1349,15 @@
NonParmVarDeclBits.ObjCForDecl = FRD;
}
- /// Determine whether this variable is an ARC pseudo-__strong
- /// variable. A pseudo-__strong variable has a __strong-qualified
- /// type but does not actually retain the object written into it.
- /// Generally such variables are also 'const' for safety.
- bool isARCPseudoStrong() const {
- return isa<ParmVarDecl>(this) ? false : NonParmVarDeclBits.ARCPseudoStrong;
- }
- void setARCPseudoStrong(bool ps) {
- assert(!isa<ParmVarDecl>(this));
- NonParmVarDeclBits.ARCPseudoStrong = ps;
- }
+ /// Determine whether this variable is an ARC pseudo-__strong variable. A
+ /// pseudo-__strong variable has a __strong-qualified type but does not
+ /// actually retain the object written into it. Generally such variables are
+ /// also 'const' for safety. There are 3 cases where this will be set, 1) if
+ /// the variable is annotated with the objc_externally_retained attribute, 2)
+ /// if its 'self' in a non-init method, or 3) if its the variable in an for-in
+ /// loop.
+ bool isARCPseudoStrong() const { return VarDeclBits.ARCPseudoStrong; }
+ void setARCPseudoStrong(bool PS) { VarDeclBits.ARCPseudoStrong = PS; }
/// Whether this variable is (C++1z) inline.
bool isInline() const {
Index: clang/docs/AutomaticReferenceCounting.rst
===================================================================
--- clang/docs/AutomaticReferenceCounting.rst
+++ clang/docs/AutomaticReferenceCounting.rst
@@ -1734,20 +1734,29 @@
rest of the language. Not draining the pool during an unwind is apparently
required by the Objective-C exceptions implementation.
+.. _arc.misc.externally_retained:
+
+``objc_externally_retained`` attribute
+--------------------------------------
+
+If a strong variable is annotated with the ``objc_externally_retained``
+attribute, then the implementation considers the variable to be
+externally-retained. This means that the implementation can assume that the
+variable is retained elsewhere, and therefore can elide retaining and releasing
+it's value. Such a variable is implicitly ``const`` for safety.
+``objc_externally_retained`` can apply to local variables, or to parameters via
+a function definitions.
+
.. _arc.misc.self:
``self``
--------
-The ``self`` parameter variable of an Objective-C method is never actually
-retained by the implementation. It is undefined behavior, or at least
-dangerous, to cause an object to be deallocated during a message send to that
-object.
-
-To make this safe, for Objective-C instance methods ``self`` is implicitly
-``const`` unless the method is in the :ref:`init family
-<arc.family.semantics.init>`. Further, ``self`` is **always** implicitly
-``const`` within a class method.
+The ``self`` parameter variable of an non-init Objective-C method is considered
+:ref:`externally-retained <arc.misc.externally_retained>` by the implementation.
+It is undefined behavior, or at least dangerous, to cause an object to be
+deallocated during a message send to that object. In an init method, ``self``
+follows the :ref:``init family rules <arc.family.semantics.init>``.
.. admonition:: Rationale
@@ -1758,9 +1767,9 @@
without this retain and release. Since it's extremely uncommon to actually
do so, even unintentionally, and since there's no natural way for the
programmer to remove this retain/release pair otherwise (as there is for
- other parameters by, say, making the variable ``__unsafe_unretained``), we
- chose to make this optimizing assumption and shift some amount of risk to the
- user.
+ other parameters by, say, making the variable ``objc_externally_retained`` or
+ qualifying it with ``__unsafe_unretained``), we chose to make this optimizing
+ assumption and shift some amount of risk to the user.
.. _arc.misc.enumeration:
@@ -1769,8 +1778,9 @@
If a variable is declared in the condition of an Objective-C fast enumeration
loop, and the variable has no explicit ownership qualifier, then it is
-qualified with ``const __strong`` and objects encountered during the
-enumeration are not actually retained.
+implicitly :ref:`externally-retained <arc.misc.externally_retained>` so that
+objects encountered during the enumeration are not actually retained and
+released.
.. admonition:: Rationale
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