Implement a new 'availability' attribute, that allows one to specify

which versions of an OS provide a certain facility. For example,

  void foo()
  __attribute__((availability(macosx,introduced=10.2,deprecated=10.4,obsoleted=10.6)));

says that the function "foo" was introduced in 10.2, deprecated in
10.4, and completely obsoleted in 10.6. This attribute ties in with
the deployment targets (e.g., -mmacosx-version-min=10.1 specifies that
we want to deploy back to Mac OS X 10.1). There are several concrete
behaviors that this attribute enables, as illustrated with the
function foo() above:

  - If we choose a deployment target >= Mac OS X 10.4, uses of "foo"
    will result in a deprecation warning, as if we had placed
    attribute((deprecated)) on it (but with a better diagnostic)
  - If we choose a deployment target >= Mac OS X 10.6, uses of "foo"
    will result in an "unavailable" warning (in C)/error (in C++), as
    if we had placed attribute((unavailable)) on it
  - If we choose a deployment target prior to 10.2, foo() is
    weak-imported (if it is a kind of entity that can be weak
    imported), as if we had placed the weak_import attribute on it.

Naturally, there can be multiple availability attributes on a
declaration, for different platforms; only the current platform
matters when checking availability attributes.

The only platforms this attribute currently works for are "ios" and
"macosx", since we already have -mxxxx-version-min flags for them and we
have experience there with macro tricks translating down to the
deprecated/unavailable/weak_import attributes. The end goal is to open
this up to other platforms, and even extension to other "platforms"
that are really libraries (say, through a #pragma clang
define_system), but that hasn't yet been designed and we may want to
shake out more issues with this narrower problem first.

Addresses <rdar://problem/6690412>.

As a drive-by bug-fix, if an entity is both deprecated and
unavailable, we only emit the "unavailable" diagnostic.

llvm-svn: 128127

1 files changed, 5 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 607df6d0b80..a4d95d443fa 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -5018,14 +5018,14 @@ void CGObjCNonFragileABIMac::GenerateClass(const ObjCImplementationDecl *ID) {
     while (const ObjCInterfaceDecl *Super = Root->getSuperClass())
       Root = Super;
     IsAGV = GetClassGlobal(ObjCMetaClassName + Root->getNameAsString());
-    if (Root->hasAttr<WeakImportAttr>())
+    if (Root->isWeakImported())
       IsAGV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
     // work on super class metadata symbol.
     std::string SuperClassName =
       ObjCMetaClassName + 
         ID->getClassInterface()->getSuperClass()->getNameAsString();
     SuperClassGV = GetClassGlobal(SuperClassName);
-    if (ID->getClassInterface()->getSuperClass()->hasAttr<WeakImportAttr>())
+    if (ID->getClassInterface()->getSuperClass()->isWeakImported())
       SuperClassGV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
   }
   llvm::GlobalVariable *CLASS_RO_GV = BuildClassRoTInitializer(flags,
@@ -5055,7 +5055,7 @@ void CGObjCNonFragileABIMac::GenerateClass(const ObjCImplementationDecl *ID) {
     std::string RootClassName =
       ID->getClassInterface()->getSuperClass()->getNameAsString();
     SuperClassGV = GetClassGlobal(ObjCClassName + RootClassName);
-    if (ID->getClassInterface()->getSuperClass()->hasAttr<WeakImportAttr>())
+    if (ID->getClassInterface()->getSuperClass()->isWeakImported())
       SuperClassGV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
   }
   GetClassSizeInfo(ID, InstanceStart, InstanceSize);
@@ -5137,7 +5137,7 @@ void CGObjCNonFragileABIMac::GenerateCategory(const ObjCCategoryImplDecl *OCD) {
   Values[0] = GetClassName(OCD->getIdentifier());
   // meta-class entry symbol
   llvm::GlobalVariable *ClassGV = GetClassGlobal(ExtClassName);
-  if (Interface->hasAttr<WeakImportAttr>())
+  if (Interface->isWeakImported())
     ClassGV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
   
   Values[1] = ClassGV;
@@ -5810,7 +5810,7 @@ llvm::Value *CGObjCNonFragileABIMac::EmitMetaClassRef(CGBuilderTy &Builder,
 /// decl.
 llvm::Value *CGObjCNonFragileABIMac::GetClass(CGBuilderTy &Builder,
                                               const ObjCInterfaceDecl *ID) {
-  if (ID->hasAttr<WeakImportAttr>()) {
+  if (ID->isWeakImported()) {
     std::string ClassName(getClassSymbolPrefix() + ID->getNameAsString());
     llvm::GlobalVariable *ClassGV = GetClassGlobal(ClassName);
     ClassGV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);