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Implement a new 'availability' attribute, that allows one to specify

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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
This commit is contained in:
Douglas Gregor
2011-03-23 00:50:03 +00:00
parent cfc332cc43
commit 20b2ebd785
45 changed files with 1063 additions and 112 deletions
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6
clang/lib/CodeGen/CodeGenModule.cpp
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@@ -509,7 +509,7 @@ void CodeGenModule::SetFunctionAttributes(GlobalDecl GD,
if (FD->hasAttr<DLLImportAttr>()) {
F->setLinkage(llvm::Function::DLLImportLinkage);
} else if (FD->hasAttr<WeakAttr>() ||
FD->hasAttr<WeakImportAttr>()) {
FD->isWeakImported()) {
// "extern_weak" is overloaded in LLVM; we probably should have
// separate linkage types for this.
F->setLinkage(llvm::Function::ExternalWeakLinkage);
@@ -986,7 +986,7 @@ CodeGenModule::GetOrCreateLLVMGlobal(llvm::StringRef MangledName,
} else {
if (D->hasAttr<DLLImportAttr>())
GV->setLinkage(llvm::GlobalValue::DLLImportLinkage);
else if (D->hasAttr<WeakAttr>() || D->hasAttr<WeakImportAttr>())
else if (D->hasAttr<WeakAttr>() || D->isWeakImported())
GV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
// Set visibility on a declaration only if it's explicit.
@@ -1530,7 +1530,7 @@ void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
}
} else if (D->hasAttr<WeakAttr>() ||
D->hasAttr<WeakRefAttr>() ||
D->hasAttr<WeakImportAttr>()) {
D->isWeakImported()) {
GA->setLinkage(llvm::Function::WeakAnyLinkage);
}