[Availability] Improve availability to consider functions run at load time

[steven_wu]

Summary

There are some functions/methods that run when the application launches
or the library loads. Those functions will run reguardless the OS
version as long as it satifies the minimum deployment target. Annotate
them with availability attributes doesn't really make sense because they
are essentially available on all targets since minimum deployment
target.

rdar://problem/36093384

[erik.pilkington]

Hi Steven, thanks for working on this!

include/clang/Basic/DiagnosticSemaKinds.td

2916

typo: destructor

lib/Sema/SemaDecl.cpp

9134–9151

Shouldn't this be in ProcessDeclAttributeList in SemaDeclAttr.cpp?

9136

Can't this just be: if (NewFD->hasAttr<AvailabilityAttr>())?

lib/Sema/SemaDeclAttr.cpp

6828

getNameAsString is deprecated, maybe you should get this from MethodD->getSelector()?

lib/Sema/SemaDeclObjC.cpp

4737–4738

Second sentence might read better as "It get called on startup, so it has to have the availability of the deployment target".

4739–4740

This should also be if (ObjCMethod->hasAttr<AvailabilityAttr>)

4744

Same comment as above!

test/SemaObjC/unguarded-availability.m

334

Could you add a test that +(void)load: (int)x; still works? It should still accept availability attributes, right?

[steven_wu]

Thanks for reviewing Erik!

lib/Sema/SemaDecl.cpp

9134–9151

This has to happen after mergeDeclAttributes, otherwise, you won't catch the case which the availability attributes and constructor attributes are on different decl that gets merged. It can't be in mergeDeclAttributes as well, then it won't catch the case they are on a single decl.

9136

The location of the diagnostics need to be on attributes and that is why it is a for loop.

[steven_wu]

Address review feedback. Fix typos and comments.

[erik.pilkington]

LGTM, thanks!

lib/Sema/SemaDecl.cpp

9134–9151

Ah, okay. Makes sense.

9136

Maybe if (auto *AA = NewFD->getAttr<AvailabilityAttr>()) then?

[steven_wu]

Address review feedback

include/clang/Basic/DiagnosticSemaKinds.td

def warn_mismatched_availability_override : Warning<
   "deprecated before|obsoleted before}0 "
   "%select{the protocol method it implements|overridden method}4 "
   "on %1 (%2 vs. %3)">, InGroup<Availability>;
 def warn_mismatched_availability_override_unavail : Warning<
   "%select{|overriding }1method cannot be unavailable on %0 when "
   "%select{the protocol method it implements|its overridden method}1 is "
   "available">,
   InGroup<Availability>;
+def warn_availability_on_static_initializer : Warning<
+  "ignoring availability attribute %select{on '+load' method|"
+  "with constructor attribute|with destructor attribute}0">,
+  InGroup<Availability>;
 def note_overridden_method : Note<
   "overridden method is here">;
 def note_protocol_method : Note<
   "protocol method is here">;
 
 def warn_unguarded_availability :
   Warning<"%0 is only available on %1 %2 or newer">,
   InGroup<UnguardedAvailability>, DefaultIgnore;

lib/Sema/SemaDecl.cpp

ClassScopeFunctionSpecializationDecl *NewSpec =
                          ClassScopeFunctionSpecializationDecl::Create(
                                 Context, CurContext, NewFD->getLocation(),
                                 cast<CXXMethodDecl>(NewFD),
                                 HasExplicitTemplateArgs, TemplateArgs);
     CurContext->addDecl(NewSpec);
     AddToScope = false;
   }
 
+  // Diagnose availability attributes. Availability cannot be used on functions
+  // that are run during load/unload.
+  if (const auto *attr = NewFD->getAttr<AvailabilityAttr>()) {
+    if (NewFD->hasAttr<ConstructorAttr>()) {
+      Diag(attr->getLocation(), diag::warn_availability_on_static_initializer)
+          << 1;
+      NewFD->dropAttr<AvailabilityAttr>();
+    }
+    if (NewFD->hasAttr<DestructorAttr>()) {
+      Diag(attr->getLocation(), diag::warn_availability_on_static_initializer)
+          << 2;
+      NewFD->dropAttr<AvailabilityAttr>();
+    }
+  }
+
   return NewFD;
 }
 
 /// \brief Checks if the new declaration declared in dependent context must be
 /// put in the same redeclaration chain as the specified declaration.
 ///
 /// \param D Declaration that is checked.
 /// \param PrevDecl Previous declaration found with proper lookup method for the
 ///                 same declaration name.
 /// \returns True if D must be added to the redeclaration chain which PrevDecl
 ///          belongs to.

lib/Sema/SemaDeclAttr.cpp

auto CheckContext = [&](const Decl *C) {
     return false;
   };
 
   do {
     if (CheckContext(Ctx))
       return false;
 
     // An implementation implicitly has the availability of the interface.
+    // Unless it is "+load" method.
+    if (const auto *MethodD = dyn_cast<ObjCMethodDecl>(Ctx))
+      if (MethodD->isClassMethod() &&
+          MethodD->getSelector().getAsString() == "load")
+        return true;
+
     if (const auto *CatOrImpl = dyn_cast<ObjCImplDecl>(Ctx)) {
       if (const ObjCInterfaceDecl *Interface = CatOrImpl->getClassInterface())
         if (CheckContext(Interface))
           return false;
     }
     // A category implicitly has the availability of the interface.
     else if (const auto *CatD = dyn_cast<ObjCCategoryDecl>(Ctx))
       if (const ObjCInterfaceDecl *Interface = CatD->getClassInterface())

lib/Sema/SemaDeclObjC.cpp

if (InferRelatedResultType &&
         !ObjCMethod->getReturnType()->isObjCIndependentClassType())
       ObjCMethod->SetRelatedResultType();
   }
 
   if (MethodDefinition &&
       Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
     checkObjCMethodX86VectorTypes(*this, ObjCMethod);
 
+  // + load method cannot have availability attributes. It get called on
+  // startup, so it has to have the availability of the deployment target.
+  if (const auto *attr = ObjCMethod->getAttr<AvailabilityAttr>()) {
+    if (ObjCMethod->isClassMethod() &&
+        ObjCMethod->getSelector().getAsString() == "load") {
+      Diag(attr->getLocation(), diag::warn_availability_on_static_initializer)
+          << 0;
+      ObjCMethod->dropAttr<AvailabilityAttr>();
+    }
+  }
+
   ActOnDocumentableDecl(ObjCMethod);
 
   return ObjCMethod;
 }
 
 bool Sema::CheckObjCDeclScope(Decl *D) {
   // Following is also an error. But it is caused by a missing @end
   // and diagnostic is issued elsewhere.

test/SemaObjC/unguarded-availability.m

 // RUN: %clang_cc1 -triple x86_64-apple-macosx-10.9 -Wunguarded-availability -fblocks -fsyntax-only -verify %s
 // RUN: %clang_cc1 -xobjective-c++ -std=c++11 -DOBJCPP -triple x86_64-apple-macosx-10.9 -Wunguarded-availability -fblocks -fsyntax-only -verify %s
 
 #define AVAILABLE_10_0  __attribute__((availability(macos, introduced = 10.0)))
 #define AVAILABLE_10_11 __attribute__((availability(macos, introduced = 10.11)))
 #define AVAILABLE_10_12 __attribute__((availability(macos, introduced = 10.12)))
 
 typedef int AVAILABLE_10_12 new_int; // expected-note + {{marked partial here}}
 
-int func_10_11() AVAILABLE_10_11; // expected-note 4 {{'func_10_11' has been explicitly marked partial here}}
+int func_10_11() AVAILABLE_10_11; // expected-note 8 {{'func_10_11' has been explicitly marked partial here}}
 
 #ifdef OBJCPP
 // expected-note@+2 6 {{marked partial here}}
 #endif
 int func_10_12() AVAILABLE_10_12; // expected-note 7 {{'func_10_12' has been explicitly marked partial here}}
 
 int func_10_0() AVAILABLE_10_0;
 
void switchAnimals(Animals a) {
   case AK_Dodo...AK_CyborgCat: // expected-warning {{'AK_Dodo' is depr}}
     break;
   }
 
   (void)AK_Dodo; // expected-warning{{'AK_Dodo' is deprecated}}
   (void)AK_Cat; // no warning
   (void)AK_CyborgCat; // expected-warning{{'AK_CyborgCat' is only available on macOS 10.12 or newer}} expected-note {{@available}}
 }
+
+
+// test static initializers has the same availability as the deployment target and it cannot be overwritten.
+@interface HasStaticInitializer : BaseClass
++ (void)load AVAILABLE_10_11; // expected-warning{{ignoring availability attribute on '+load' method}}
+@end
+
+@implementation HasStaticInitializer
++ (void)load {
+  func_10_11(); // expected-warning{{'func_10_11' is only available on macOS 10.11 or newer}} expected-note{{enclose 'func_10_11' in an @available check to silence this warning}}
+}
+@end
+
+// test availability from interface is ignored when checking the unguarded availability in +load method.
+AVAILABLE_10_11
+@interface HasStaticInitializer1 : BaseClass
++ (void)load;
++ (void)load: (int)x; // no warning.
+@end
+
+@implementation HasStaticInitializer1
++ (void)load {
+  func_10_11(); // expected-warning{{'func_10_11' is only available on macOS 10.11 or newer}} expected-note{{enclose 'func_10_11' in an @available check to silence this warning}}
+}
++ (void)load: (int)x {
+  func_10_11(); // no warning.
+}
+@end
+
+__attribute__((constructor))
+void is_constructor();
+
+AVAILABLE_10_11 // expected-warning{{ignoring availability attribute with constructor attribute}}
+void is_constructor() {
+  func_10_11(); // expected-warning{{'func_10_11' is only available on macOS 10.11 or newer}} expected-note{{enclose 'func_10_11' in an @available check to silence this warning}}
+}
+
+AVAILABLE_10_11 // expected-warning{{ignoring availability attribute with destructor attribute}}
+__attribute__((destructor))
+void is_destructor() {
+  func_10_11(); // expected-warning{{'func_10_11' is only available on macOS 10.11 or newer}} expected-note{{enclose 'func_10_11' in an @available check to silence this warning}}
+}