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, 14 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 877650f9de3..482ce4bec7c 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -37,6 +37,7 @@
 #include "clang/Basic/SourceManagerInternals.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/Version.h"
+#include "clang/Basic/VersionTuple.h"
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/StringExtras.h"
@@ -2622,6 +2623,19 @@ void ASTWriter::AddString(llvm::StringRef Str, RecordDataImpl &Record) {
   Record.insert(Record.end(), Str.begin(), Str.end());
 }
 
+void ASTWriter::AddVersionTuple(const VersionTuple &Version,
+                                RecordDataImpl &Record) {
+  Record.push_back(Version.getMajor());
+  if (llvm::Optional<unsigned> Minor = Version.getMinor())
+    Record.push_back(*Minor + 1);
+  else
+    Record.push_back(0);
+  if (llvm::Optional<unsigned> Subminor = Version.getSubminor())
+    Record.push_back(*Subminor + 1);
+  else
+    Record.push_back(0);
+}
+
 /// \brief Note that the identifier II occurs at the given offset
 /// within the identifier table.
 void ASTWriter::SetIdentifierOffset(const IdentifierInfo *II, uint32_t Offset) {