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, 13 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index b34b62ab6f3..1b55f71c36b 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -37,6 +37,7 @@
 #include "clang/Basic/FileSystemStatCache.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/Version.h"
+#include "clang/Basic/VersionTuple.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Bitcode/BitstreamReader.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -4870,6 +4871,18 @@ std::string ASTReader::ReadString(const RecordData &Record, unsigned &Idx) {
   return Result;
 }
 
+VersionTuple ASTReader::ReadVersionTuple(const RecordData &Record, 
+                                         unsigned &Idx) {
+  unsigned Major = Record[Idx++];
+  unsigned Minor = Record[Idx++];
+  unsigned Subminor = Record[Idx++];
+  if (Minor == 0)
+    return VersionTuple(Major);
+  if (Subminor == 0)
+    return VersionTuple(Major, Minor - 1);
+  return VersionTuple(Major, Minor - 1, Subminor - 1);
+}
+
 CXXTemporary *ASTReader::ReadCXXTemporary(const RecordData &Record,
                                           unsigned &Idx) {
   CXXDestructorDecl *Decl = cast<CXXDestructorDecl>(GetDecl(Record[Idx++]));