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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128127 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 62 insertions, 0 deletions

diff --git a/include/clang/Sema/AttributeList.h b/include/clang/Sema/AttributeList.h
index 382e50494e..3657b44b02 100644
--- a/include/clang/Sema/AttributeList.h
+++ b/include/clang/Sema/AttributeList.h
@@ -18,6 +18,7 @@
 #include "llvm/Support/Allocator.h"
 #include "clang/Sema/Ownership.h"
 #include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/VersionTuple.h"
 #include "clang/AST/Expr.h"
 #include <cassert>
 
@@ -25,6 +26,23 @@ namespace clang {
   class IdentifierInfo;
   class Expr;
 
+/// \brief Represents information about a change in availability for
+/// an entity, which is part of the encoding of the 'availability'
+/// attribute.
+struct AvailabilityChange {
+  /// \brief The location of the keyword indicating the kind of change.
+  SourceLocation KeywordLoc;
+
+  /// \brief The version number at which the change occurred.
+  VersionTuple Version;
+
+  /// \brief The source range covering the version number.
+  SourceRange VersionRange;
+
+  /// \brief Determine whether this availability change is valid.
+  bool isValid() const { return !Version.empty(); }
+};
+
 /// AttributeList - Represents GCC's __attribute__ declaration. There are
 /// 4 forms of this construct...they are:
 ///
@@ -48,6 +66,11 @@ private:
   AttributeList *Next;
   bool DeclspecAttribute, CXX0XAttribute;
 
+  // For the 'availability' attribute.
+  AvailabilityChange AvailabilityIntroduced;
+  AvailabilityChange AvailabilityDeprecated;
+  AvailabilityChange AvailabilityObsoleted;
+
   /// True if already diagnosed as invalid.
   mutable bool Invalid;
 
@@ -61,6 +84,15 @@ private:
                 IdentifierInfo *ParmName, SourceLocation ParmLoc,
                 Expr **args, unsigned numargs,
                 bool declspec, bool cxx0x);
+
+  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);
 public:
   class Factory {
     llvm::BumpPtrAllocator Alloc;
@@ -78,6 +110,20 @@ public:
         return Mem;
       }
 
+    AttributeList *Create(IdentifierInfo *AttrName, SourceLocation AttrLoc,
+      IdentifierInfo *ScopeName, SourceLocation ScopeLoc,
+      IdentifierInfo *ParmName, SourceLocation ParmLoc,
+      const AvailabilityChange &Introduced,
+      const AvailabilityChange &Deprecated,
+      const AvailabilityChange &Obsoleted,
+      bool declspec = false, bool cxx0x = false) {
+        AttributeList *Mem = Alloc.Allocate<AttributeList>();
+        new (Mem) AttributeList(Alloc, AttrName, AttrLoc, ScopeName, ScopeLoc,
+                                ParmName, ParmLoc, Introduced, Deprecated,
+                                Obsoleted, declspec, cxx0x);
+        return Mem;
+      }
+
     AttributeList* CreateIntegerAttribute(ASTContext &C, IdentifierInfo *Name,
                                           SourceLocation TokLoc, int Arg) {
       Expr* IArg = IntegerLiteral::Create(C, llvm::APInt(32, (uint64_t)Arg),
@@ -96,6 +142,7 @@ public:
     AT_always_inline,
     AT_analyzer_noreturn,
     AT_annotate,
+    AT_availability,      // Clang-specific
     AT_base_check,
     AT_blocks,
     AT_carries_dependency,
@@ -244,6 +291,21 @@ public:
   arg_iterator arg_end() const {
     return arg_iterator(Args, NumArgs);
   }
+
+  const AvailabilityChange &getAvailabilityIntroduced() const {
+    assert(getKind() == AT_availability && "Not an availability attribute");
+    return AvailabilityIntroduced;
+  }
+
+  const AvailabilityChange &getAvailabilityDeprecated() const {
+    assert(getKind() == AT_availability && "Not an availability attribute");
+    return AvailabilityDeprecated;
+  }
+
+  const AvailabilityChange &getAvailabilityObsoleted() const {
+    assert(getKind() == AT_availability && "Not an availability attribute");
+    return AvailabilityObsoleted;
+  }
 };
 
 /// addAttributeLists - Add two AttributeLists together