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, 12 insertions, 3 deletions

diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 653cf80688d..90b0ee0c87e 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -76,7 +76,9 @@ public:
 
 
 static void getDarwinDefines(MacroBuilder &Builder, const LangOptions &Opts,
-                             const llvm::Triple &Triple) {
+                             const llvm::Triple &Triple,
+                             llvm::StringRef &PlatformName,
+                             VersionTuple &PlatformMinVersion) {
   Builder.defineMacro("__APPLE_CC__", "5621");
   Builder.defineMacro("__APPLE__");
   Builder.defineMacro("__MACH__");
@@ -120,6 +122,9 @@ static void getDarwinDefines(MacroBuilder &Builder, const LangOptions &Opts,
     Str[4] = '0' + (Rev % 10);
     Str[5] = '\0';
     Builder.defineMacro("__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__", Str);
+
+    PlatformName = "ios";
+    PlatformMinVersion = VersionTuple(Maj, Min, Rev);
   } else {
     // For historical reasons that make little sense, the version passed here is
     // the "darwin" version, which drops the 10 and offsets by 4.
@@ -136,6 +141,9 @@ static void getDarwinDefines(MacroBuilder &Builder, const LangOptions &Opts,
     Str[3] = '0' + Rev;
     Str[4] = '\0';
     Builder.defineMacro("__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__", Str);
+
+    PlatformName = "macosx";
+    PlatformMinVersion = VersionTuple(Maj, Min, Rev);
   }
 }
 
@@ -145,7 +153,8 @@ class DarwinTargetInfo : public OSTargetInfo<Target> {
 protected:
   virtual void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                             MacroBuilder &Builder) const {
-    getDarwinDefines(Builder, Opts, Triple);
+    getDarwinDefines(Builder, Opts, Triple, this->PlatformName, 
+                     this->PlatformMinVersion);
   }
 
 public:
@@ -2005,7 +2014,7 @@ class DarwinARMTargetInfo :
 protected:
   virtual void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                             MacroBuilder &Builder) const {
-    getDarwinDefines(Builder, Opts, Triple);
+    getDarwinDefines(Builder, Opts, Triple, PlatformName, PlatformMinVersion);
   }
 
 public: