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, 36 insertions, 0 deletions

diff --git a/clang/lib/Basic/VersionTuple.cpp b/clang/lib/Basic/VersionTuple.cpp
new file mode 100644
index 00000000000..d5cf126ff48
--- /dev/null
+++ b/clang/lib/Basic/VersionTuple.cpp
@@ -0,0 +1,36 @@
+//===- VersionTuple.cpp - Version Number Handling ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the VersionTuple class, which represents a version in
+// the form major[.minor[.subminor]].
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Basic/VersionTuple.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+
+std::string VersionTuple::getAsString() const {
+  std::string Result;
+  {
+    llvm::raw_string_ostream Out(Result);
+    Out << *this;
+  }
+  return Result;
+}
+
+llvm::raw_ostream& clang::operator<<(llvm::raw_ostream &Out, 
+                                     const VersionTuple &V) {
+  Out << V.getMajor();
+  if (llvm::Optional<unsigned> Minor = V.getMinor())
+    Out << '.' << *Minor;
+  if (llvm::Optional<unsigned> Subminor = V.getSubminor())
+    Out << '.' << *Subminor;
+  return Out;
+}