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, 19 insertions, 0 deletions

diff --git a/clang/lib/Sema/AttributeList.cpp b/clang/lib/Sema/AttributeList.cpp
index a715989c685..ae5ea673eba 100644
--- a/clang/lib/Sema/AttributeList.cpp
+++ b/clang/lib/Sema/AttributeList.cpp
@@ -36,6 +36,24 @@ AttributeList::AttributeList(llvm::BumpPtrAllocator &Alloc,
   }
 }
 
+AttributeList::AttributeList(llvm::BumpPtrAllocator &Alloc,
+                             IdentifierInfo *AttrName, SourceLocation AttrLoc,
+                             IdentifierInfo *ScopeName, SourceLocation ScopeLoc,
+                             IdentifierInfo *ParmName, SourceLocation ParmLoc,
+                             const AvailabilityChange &Introduced,
+                             const AvailabilityChange &Deprecated,
+                             const AvailabilityChange &Obsoleted,
+                             bool declspec, bool cxx0x)
+  : AttrName(AttrName), AttrLoc(AttrLoc), ScopeName(ScopeName), 
+    ScopeLoc(ScopeLoc), ParmName(ParmName), ParmLoc(ParmLoc), 
+    Args(0), NumArgs(0), Next(0),
+    DeclspecAttribute(declspec), CXX0XAttribute(cxx0x), 
+    AvailabilityIntroduced(Introduced),
+    AvailabilityDeprecated(Deprecated),
+    AvailabilityObsoleted(Obsoleted),
+    Invalid(false) {
+}
+
 AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
   llvm::StringRef AttrName = Name->getName();
 
@@ -83,6 +101,7 @@ AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
     .Case("may_alias", AT_may_alias)
     .Case("base_check", AT_base_check)
     .Case("deprecated", AT_deprecated)
+    .Case("availability", AT_availability)
     .Case("visibility", AT_visibility)
     .Case("destructor", AT_destructor)
     .Case("format_arg", AT_format_arg)