Add a new flag and attributes to control static destructor registration

[erik.pilkington]

Summary

See the recent thread here: http://lists.llvm.org/pipermail/cfe-dev/2018-July/058494.html

This patch adds the flag -fno-c++-static-destructors, which disables registration of exit-time destructors of static or thread storage duration variables. This patch also adds [[clang::no_destroy]] and [[clang::always_destroy]] attributes for disabling dtors in -fc++-static-destructors mode, and enabling dtors in -fno-c++-static-destructors mode, respectively. This patch was based on @bruno's https://reviews.llvm.org/D22474.

rdar://21734598

Thanks for taking a look!
Erik

[jfb]

clang/include/clang/AST/Decl.h

1472 ↗

(On Diff #161548)

This is only valid for static variables, right? It's probably better to document the function name that way, e.g. isStaticWithNoDestroy.

clang/include/clang/Basic/Attr.td

2999 ↗

(On Diff #161548)

Ditto for these, I think the names of the variables should clarify that it's only for static. Note that I wouldn't rename the attributes themselves! Usage in context is unambiguous, and the docs should be clear. I just think the variable names don't provide the required context.

clang/include/clang/Basic/AttrDocs.td

3494 ↗

(On Diff #161548)

"its"

3495 ↗

(On Diff #161548)

"does nothing" is more "is the default".

3503 ↗

(On Diff #161548)

"its"

3504 ↗

(On Diff #161548)

"static and thread"

clang/lib/Sema/SemaDeclAttr.cpp

5931 ↗

(On Diff #161548)

This allows a variable with both attributes :)
Looking at the code above it seems like having both attributes is equivalent to no-destroy.

[rsmith]

clang/include/clang/AST/Decl.h

1472 ↗

(On Diff #161548)

I think the question (and hence current function name) is meaningful for any variable, but it just happens that the answer will always be "no" for non-static variables (for now, at least). Are you concerned that people will think calls to this function are missing from codepaths that only deal with automatic storage duration variables with the current name?

clang/include/clang/Basic/Attr.td

2999 ↗

(On Diff #161548)

Our convention is that the Attr name matches the source spelling, so I think this is appropriate as-is.

clang/include/clang/Basic/DiagnosticSemaKinds.td

1813 ↗

(On Diff #161548)

"must" -> "can only". (There is no requirement to apply the attribute to anything.)

clang/include/clang/Basic/LangOptions.def

311 ↗

(On Diff #161548)

Should be a BENIGN_LANGOPT because it doesn't affect AST construction, only the generated code.

clang/lib/Frontend/CompilerInvocation.cpp

2769–2771 ↗

(On Diff #161548)

-fc++-static-destructors is not a CC1 flag, so this should just be a hasArg call.

[jfb]

clang/include/clang/AST/Decl.h

1472 ↗

(On Diff #161548)

Yeah it seems like "this variable has no destructor". I guess even trivial automatic variables have a (trivial) destructor, so maybe it's not ambiguous? Up to y'all :)

[erik.pilkington]

In this new patch:

• Fix some grammar errors in the documentation.
• Add a testcase for both attributes appearing on a variable.
• Just use hasArg() in the driver.
• Improve the diagnostic.

Thanks for the feedback!

clang/include/clang/AST/Decl.h

1472 ↗

(On Diff #161548)

If anyone has a strong preference I'd be happy either way!

clang/include/clang/Basic/LangOptions.def

311 ↗

(On Diff #161548)

It does affect AST construction though, we don't mark a static VarDecl's type's destructor referenced in this mode, or check it's access (because we aren't actually using it). Do you think this is the wrong choice of semantics?

clang/lib/Sema/SemaDeclAttr.cpp

5931 ↗

(On Diff #161548)

handleSimpleAttributeWithExclusions handles that automagically, i.e.:

$ cat t.cpp
[[clang::no_destroy]] [[clang::always_destroy]] int x;
$ ~/dbg-bld/bin/clang t.cpp
t.cpp:1:25: error: 'always_destroy' and 'no_destroy' attributes are not compatible
[[clang::no_destroy]] [[clang::always_destroy]] int x;
                        ^
t.cpp:1:3: note: conflicting attribute is here
[[clang::no_destroy]] [[clang::always_destroy]] int x;
  ^
1 error generated.

I'll add a test to prove this though...

[rsmith]

Seems fine to me, once you add the test for always_destroy + no_destroy.

clang/include/clang/Basic/LangOptions.def

311 ↗

(On Diff #161548)

Ah, no, good point. This is right, then. (And I think avoiding checking the destructor is also appropriate, so that a private or deleted destructor can be used to "remind" people to use the attribute.)

[jfb]

clang/include/clang/AST/Decl.h

1472 ↗

(On Diff #161548)

Considering what Richard pointed out below w.r.t. naming convention, this is good with me.

clang/lib/Sema/SemaDeclAttr.cpp

5931 ↗

(On Diff #161548)

Ah nice!

[aaron.ballman]

Some minor nits that can be handled post-commit.

lib/Sema/SemaDeclAttr.cpp

5921 ↗

(On Diff #161757)

There is no need to check VarDecl here -- that's already done for you by the subject.

5927–5931 ↗

(On Diff #161757)

Elide braces.

test/SemaCXX/no_destroy.cpp

33–34 ↗

(On Diff #161757)

Please also add tests demonstrating that the attribute does not appertain to things that don't look like variables (like a function or struct declaration) and that it does not accept arguments.

[erik.pilkington]

Sure, done in 340311!

cfe/trunk/include/clang/AST/Decl.h

public:
 
   void setDescribedVarTemplate(VarTemplateDecl *Template);
 
   // Is this variable known to have a definition somewhere in the complete
   // program? This may be true even if the declaration has internal linkage and
   // has no definition within this source file.
   bool isKnownToBeDefined() const;
 
+  /// Do we need to emit an exit-time destructor for this variable?
+  bool isNoDestroy(const ASTContext &) const;
+
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) { return K >= firstVar && K <= lastVar; }
 };
 
 class ImplicitParamDecl : public VarDecl {
   void anchor() override;
 

cfe/trunk/include/clang/Basic/Attr.td

def InternalLinkage : InheritableAttr {
   let Documentation = [InternalLinkageDocs];
 }
 
 def Reinitializes : InheritableAttr {
   let Spellings = [Clang<"reinitializes", 0>];
   let Subjects = SubjectList<[NonStaticNonConstCXXMethod], ErrorDiag>;
   let Documentation = [ReinitializesDocs];
 }
+
+def NoDestroy : InheritableAttr {
+  let Spellings = [Clang<"no_destroy", 0>];
+  let Subjects = SubjectList<[Var]>;
+  let Documentation = [NoDestroyDocs];
+}
+
+def AlwaysDestroy : InheritableAttr {
+  let Spellings = [Clang<"always_destroy", 0>];
+  let Subjects = SubjectList<[Var]>;
+  let Documentation = [AlwaysDestroyDocs];
+}

cfe/trunk/include/clang/Basic/AttrDocs.td

.. code-block:: c++
   class Container {
   public:
     ...
     [[clang::reinitializes]] void Clear();
     ...
   };
   }];
 }
+
+def AlwaysDestroyDocs : Documentation {
+  let Category = DocCatVariable;
+  let Content = [{
+The ``always_destroy`` attribute specifies that a variable with static or thread
+storage duration should have its exit-time destructor run. This attribute is the
+default unless clang was invoked with -fno-c++-static-destructors.
+  }];
+}
+
+def NoDestroyDocs : Documentation {
+  let Category = DocCatVariable;
+  let Content = [{
+The ``no_destroy`` attribute specifies that a variable with static or thread
+storage duration shouldn't have its exit-time destructor run. Annotating every
+static and thread duration variable with this attribute is equivalent to
+invoking clang with -fno-c++-static-destructors.
+  }];
+}

cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td

 def err_ident_in_dtor_not_a_type : Error<
   "identifier %0 in object destruction expression does not name a type">;
 def err_destructor_expr_type_mismatch : Error<
   "destructor type %0 in object destruction expression does not match the "
   "type %1 of the object being destroyed">;
 def note_destructor_type_here : Note<
   "type %0 is declared here">;
 
+def err_destroy_attr_on_non_static_var : Error<
+  "%select{no_destroy|always_destroy}0 attribute can only be applied to a"
+  " variable with static or thread storage duration">;
+
 def err_destructor_template : Error<
   "destructor cannot be declared as a template">;
 
 // C++ initialization
 def err_init_conversion_failed : Error<
   "cannot initialize %select{a variable|a parameter|return object|"
   "statement expression result|an "
   "exception object|a member subobject|an array element|a new value|a value|a "

cfe/trunk/include/clang/Basic/LangOptions.def

ENUM_LANGOPT(ClangABICompat, ClangABI, 4, ClangABI::Latest,
              "with")
 
 COMPATIBLE_VALUE_LANGOPT(FunctionAlignment, 5, 0, "Default alignment for functions")
 
 LANGOPT(FixedPoint, 1, 0, "fixed point types")
 LANGOPT(PaddingOnUnsignedFixedPoint, 1, 0,
         "unsigned fixed point types having one extra padding bit")
 
+LANGOPT(RegisterStaticDestructors, 1, 1, "Register C++ static destructors")
+
 #undef LANGOPT
 #undef COMPATIBLE_LANGOPT
 #undef BENIGN_LANGOPT
 #undef ENUM_LANGOPT
 #undef COMPATIBLE_ENUM_LANGOPT
 #undef BENIGN_ENUM_LANGOPT
 #undef VALUE_LANGOPT
 #undef COMPATIBLE_VALUE_LANGOPT
 #undef BENIGN_VALUE_LANGOPT

cfe/trunk/include/clang/Driver/Options.td

 def fno_force_enable_int128 : Flag<["-"], "fno-force-enable-int128">,
   Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Disable support for int128_t type">;
 
 def ffixed_point : Flag<["-"], "ffixed-point">, Group<f_Group>,
                    Flags<[CC1Option]>, HelpText<"Enable fixed point types">;
 def fno_fixed_point : Flag<["-"], "fno-fixed-point">, Group<f_Group>,
                       HelpText<"Disable fixed point types">;
+def fcxx_static_destructors : Flag<["-"], "fc++-static-destructors">,
+  Group<f_Group>,
+  HelpText<"Enable C++ static destructor registration (the default)">;
+def fno_cxx_static_destructors : Flag<["-"], "fno-c++-static-destructors">,
+  Group<f_Group>,
+  Flags<[CC1Option]>,
+  HelpText<"Disable C++ static destructor registration">;
 
 // Begin sanitizer flags. These should all be core options exposed in all driver
 // modes.
 let Flags = [CC1Option, CoreOption] in {
 
 def fsanitize_EQ : CommaJoined<["-"], "fsanitize=">, Group<f_clang_Group>,
                    MetaVarName<"<check>">,
                    HelpText<"Turn on runtime checks for various forms of undefined "

cfe/trunk/lib/AST/Decl.cpp

bool VarDecl::isKnownToBeDefined() const {
   if (LangOpts.CUDA && !LangOpts.CUDARelocatableDeviceCode &&
       hasExternalStorage() && hasAttr<CUDASharedAttr>() &&
       isa<IncompleteArrayType>(getType()))
     return true;
 
   return hasDefinition();
 }
 
+bool VarDecl::isNoDestroy(const ASTContext &Ctx) const {
+  return hasGlobalStorage() && (hasAttr<NoDestroyAttr>() ||
+                                (!Ctx.getLangOpts().RegisterStaticDestructors &&
+                                 !hasAttr<AlwaysDestroyAttr>()));
+}
+
 MemberSpecializationInfo *VarDecl::getMemberSpecializationInfo() const {
   if (isStaticDataMember())
     // FIXME: Remove ?
     // return getASTContext().getInstantiatedFromStaticDataMember(this);
     return getASTContext().getTemplateOrSpecializationInfo(this)
         .dyn_cast<MemberSpecializationInfo *>();
   return nullptr;
 }

cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp

void CodeGenModule::registerGlobalDtorsWithAtExit() {
   }
 }
 
 /// Register a global destructor as best as we know how.
 void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
                                        const VarDecl &D,
                                        llvm::Constant *dtor,
                                        llvm::Constant *addr) {
+  if (D.isNoDestroy(CGM.getContext()))
+    return;
+
   // Use __cxa_atexit if available.
   if (CGM.getCodeGenOpts().CXAAtExit)
     return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
 
   if (D.getTLSKind())
     CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
 
   // In Apple kexts, we want to add a global destructor entry.

cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp

if (llvm::Function *TLRegDtorFn = dyn_cast<llvm::Function>(TLRegDtor))
     TLRegDtorFn->setDoesNotThrow();
 
   CGF.EmitNounwindRuntimeCall(TLRegDtor, DtorStub);
 }
 
 void MicrosoftCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                                          llvm::Constant *Dtor,
                                          llvm::Constant *Addr) {
+  if (D.isNoDestroy(CGM.getContext()))
+    return;
+
   if (D.getTLSKind())
     return emitGlobalDtorWithTLRegDtor(CGF, D, Dtor, Addr);
 
   // The default behavior is to use atexit.
   CGF.registerGlobalDtorWithAtExit(D, Dtor, Addr);
 }
 
 void MicrosoftCXXABI::EmitThreadLocalInitFuncs(

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

if (Arg *A = Args.getLastArg(options::OPT_fforce_enable_int128,
     if (A->getOption().matches(options::OPT_fforce_enable_int128))
       CmdArgs.push_back("-fforce-enable-int128");
   }
 
   if (Args.hasFlag(options::OPT_fcomplete_member_pointers,
                    options::OPT_fno_complete_member_pointers, false))
     CmdArgs.push_back("-fcomplete-member-pointers");
 
+  if (!Args.hasFlag(options::OPT_fcxx_static_destructors,
+                    options::OPT_fno_cxx_static_destructors, true))
+    CmdArgs.push_back("-fno-c++-static-destructors");
+
   if (Arg *A = Args.getLastArg(options::OPT_moutline,
                                options::OPT_mno_outline)) {
     if (A->getOption().matches(options::OPT_moutline)) {
       // We only support -moutline in AArch64 right now. If we're not compiling
       // for AArch64, emit a warning and ignore the flag. Otherwise, add the
       // proper mllvm flags.
       if (Triple.getArch() != llvm::Triple::aarch64) {
         D.Diag(diag::warn_drv_moutline_unsupported_opt) << Triple.getArchName();

cfe/trunk/lib/Frontend/CompilerInvocation.cpp

#include "clang/Frontend/LangStandards.def"
   Opts.XRayAttrListFiles = Args.getAllArgValues(OPT_fxray_attr_list);
 
   // -fforce-emit-vtables
   Opts.ForceEmitVTables = Args.hasArg(OPT_fforce_emit_vtables);
 
   // -fallow-editor-placeholders
   Opts.AllowEditorPlaceholders = Args.hasArg(OPT_fallow_editor_placeholders);
 
+  Opts.RegisterStaticDestructors = !Args.hasArg(OPT_fno_cxx_static_destructors);
+
   if (Arg *A = Args.getLastArg(OPT_fclang_abi_compat_EQ)) {
     Opts.setClangABICompat(LangOptions::ClangABI::Latest);
 
     StringRef Ver = A->getValue();
     std::pair<StringRef, StringRef> VerParts = Ver.split('.');
     unsigned Major, Minor = 0;
 
     // Check the version number is valid: either 3.x (0 <= x <= 9) or

cfe/trunk/lib/Sema/SemaDeclAttr.cpp

if (AL.getName()->getName().find("read_write") != StringRef::npos) {
       }
     }
   }
 
   D->addAttr(::new (S.Context) OpenCLAccessAttr(
       AL.getRange(), S.Context, AL.getAttributeSpellingListIndex()));
 }
 
+static void handleDestroyAttr(Sema &S, Decl *D, const ParsedAttr &A) {
+  if (!isa<VarDecl>(D) || !cast<VarDecl>(D)->hasGlobalStorage()) {
+    S.Diag(D->getLocation(), diag::err_destroy_attr_on_non_static_var)
+        << (A.getKind() == ParsedAttr::AT_AlwaysDestroy);
+    return;
+  }
+
+  if (A.getKind() == ParsedAttr::AT_AlwaysDestroy) {
+    handleSimpleAttributeWithExclusions<AlwaysDestroyAttr, NoDestroyAttr>(S, D, A);
+  } else {
+    handleSimpleAttributeWithExclusions<NoDestroyAttr, AlwaysDestroyAttr>(S, D, A);
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // Top Level Sema Entry Points
 //===----------------------------------------------------------------------===//
 
 /// ProcessDeclAttribute - Apply the specific attribute to the specified decl if
 /// the attribute applies to decls.  If the attribute is a type attribute, just
 /// silently ignore it if a GNU attribute.
 static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_XRayLogArgs:
     handleXRayLogArgsAttr(S, D, AL);
     break;
 
   // Move semantics attribute.
   case ParsedAttr::AT_Reinitializes:
     handleSimpleAttribute<ReinitializesAttr>(S, D, AL);
     break;
+
+  case ParsedAttr::AT_AlwaysDestroy:
+  case ParsedAttr::AT_NoDestroy:
+    handleDestroyAttr(S, D, AL);
+    break;
   }
 }
 
 /// ProcessDeclAttributeList - Apply all the decl attributes in the specified
 /// attribute list to the specified decl, ignoring any type attributes.
 void Sema::ProcessDeclAttributeList(Scope *S, Decl *D,
                                     const ParsedAttributesView &AttrList,
                                     bool IncludeCXX11Attributes) {

cfe/trunk/lib/Sema/SemaDeclCXX.cpp

 void Sema::FinalizeVarWithDestructor(VarDecl *VD, const RecordType *Record) {
   if (VD->isInvalidDecl()) return;
 
   CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(Record->getDecl());
   if (ClassDecl->isInvalidDecl()) return;
   if (ClassDecl->hasIrrelevantDestructor()) return;
   if (ClassDecl->isDependentContext()) return;
 
+  if (VD->isNoDestroy(getASTContext()))
+    return;
+
   CXXDestructorDecl *Destructor = LookupDestructor(ClassDecl);
   MarkFunctionReferenced(VD->getLocation(), Destructor);
   CheckDestructorAccess(VD->getLocation(), Destructor,
                         PDiag(diag::err_access_dtor_var)
                         << VD->getDeclName()
                         << VD->getType());
   DiagnoseUseOfDecl(Destructor, VD->getLocation());
 

cfe/trunk/test/CodeGenCXX/always_destroy.cpp

+// RUN: %clang_cc1 %s -fno-c++-static-destructors -emit-llvm -triple x86_64-apple-macosx10.13.0 -o - | FileCheck %s
+
+struct NonTrivial {
+  ~NonTrivial();
+};
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+NonTrivial nt1;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+thread_local NonTrivial nt2;
+
+struct NonTrivial2 {
+  ~NonTrivial2();
+};
+
+// CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+[[clang::always_destroy]] NonTrivial2 nt21;
+// CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+[[clang::always_destroy]] thread_local NonTrivial2 nt22;
+
+void f() {
+  // CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  [[clang::always_destroy]] static NonTrivial2 nt21;
+  // CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  [[clang::always_destroy]] thread_local NonTrivial2 nt22;
+}
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] NonTrivial nt3;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] thread_local NonTrivial nt4;

cfe/trunk/test/CodeGenCXX/no_destroy.cpp

+// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-apple-macosx10.13.0 -o - | FileCheck %s
+
+struct NonTrivial {
+  ~NonTrivial();
+};
+
+// CHECK-NOT: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] NonTrivial nt1;
+// CHECK-NOT: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::no_destroy]] thread_local NonTrivial nt2;
+
+struct NonTrivial2 {
+  ~NonTrivial2();
+};
+
+// CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+NonTrivial2 nt21;
+// CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+thread_local NonTrivial2 nt22;
+
+void f() {
+  // CHECK: __cxa_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  static NonTrivial2 nt21;
+  // CHECK: _tlv_atexit{{.*}}_ZN11NonTrivial2D1Ev
+  thread_local NonTrivial2 nt22;
+}
+
+// CHECK: __cxa_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::always_destroy]] NonTrivial nt3;
+// CHECK: _tlv_atexit{{.*}}_ZN10NonTrivialD1Ev
+[[clang::always_destroy]] thread_local NonTrivial nt4;

cfe/trunk/test/Misc/pragma-attribute-supported-attributes-list.test

 // RUN: clang-tblgen -gen-clang-test-pragma-attribute-supported-attributes -I%src_include_dir %src_include_dir/clang/Basic/Attr.td -o - | FileCheck %s
 
 // The number of supported attributes should never go down!
 
-// CHECK: #pragma clang attribute supports 72 attributes:
+// CHECK: #pragma clang attribute supports 74 attributes:
 // CHECK-NEXT: AMDGPUFlatWorkGroupSize (SubjectMatchRule_function)
 // CHECK-NEXT: AMDGPUNumSGPR (SubjectMatchRule_function)
 // CHECK-NEXT: AMDGPUNumVGPR (SubjectMatchRule_function)
 // CHECK-NEXT: AMDGPUWavesPerEU (SubjectMatchRule_function)
 // CHECK-NEXT: AVRSignal (SubjectMatchRule_function)
 // CHECK-NEXT: AbiTag (SubjectMatchRule_record_not_is_union, SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_namespace)
 // CHECK-NEXT: AlignValue (SubjectMatchRule_variable, SubjectMatchRule_type_alias)
 // CHECK-NEXT: AllocSize (SubjectMatchRule_function)
+// CHECK-NEXT: AlwaysDestroy (SubjectMatchRule_variable)
 // CHECK-NEXT: Annotate ()
 // CHECK-NEXT: AnyX86NoCfCheck (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: AssumeAligned (SubjectMatchRule_objc_method, SubjectMatchRule_function)
 // CHECK-NEXT: Availability ((SubjectMatchRule_record, SubjectMatchRule_enum, SubjectMatchRule_enum_constant, SubjectMatchRule_field, SubjectMatchRule_function, SubjectMatchRule_namespace, SubjectMatchRule_objc_category, SubjectMatchRule_objc_interface, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_objc_protocol, SubjectMatchRule_record, SubjectMatchRule_type_alias, SubjectMatchRule_variable))
 // CHECK-NEXT: CPUDispatch (SubjectMatchRule_function)
 // CHECK-NEXT: CPUSpecific (SubjectMatchRule_function)
 // CHECK-NEXT: CXX11NoReturn (SubjectMatchRule_function)
 // CHECK-NEXT: CallableWhen (SubjectMatchRule_function_is_member)

 // CHECK-NEXT: IFunc (SubjectMatchRule_function)
 // CHECK-NEXT: InternalLinkage (SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_record)
 // CHECK-NEXT: LTOVisibilityPublic (SubjectMatchRule_record)
 // CHECK-NEXT: MicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: MinVectorWidth (SubjectMatchRule_function)
 // CHECK-NEXT: MipsLongCall (SubjectMatchRule_function)
 // CHECK-NEXT: MipsShortCall (SubjectMatchRule_function)
 // CHECK-NEXT: NoDebug (SubjectMatchRule_hasType_functionType, SubjectMatchRule_objc_method, SubjectMatchRule_variable_not_is_parameter)
+// CHECK-NEXT: NoDestroy (SubjectMatchRule_variable)
 // CHECK-NEXT: NoDuplicate (SubjectMatchRule_function)
 // CHECK-NEXT: NoEscape (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: NoMicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: NoSanitize (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_variable_is_global)
 // CHECK-NEXT: NoSanitizeSpecific (SubjectMatchRule_function, SubjectMatchRule_variable_is_global)
 // CHECK-NEXT: NoSplitStack (SubjectMatchRule_function)
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_function)

cfe/trunk/test/SemaCXX/no_destroy.cpp

+// RUN: %clang_cc1 -DNO_DTORS -fno-c++-static-destructors -verify %s
+// RUN: %clang_cc1 -verify %s
+
+struct SecretDestructor {
+#ifndef NO_DTORS
+  // expected-note@+2 4 {{private}}
+#endif
+private: ~SecretDestructor(); // expected-note 2 {{private}}
+};
+
+SecretDestructor sd1;
+thread_local SecretDestructor sd2;
+void locals() {
+  static SecretDestructor sd3;
+  thread_local SecretDestructor sd4;
+}
+
+#ifndef NO_DTORS
+// SecretDestructor sd1;                  // expected-error@-8 {{private}}
+// thread_local SecretDestructor sd2;     // expected-error@-8 {{private}}
+// void locals() {
+//   static SecretDestructor sd3;         // expected-error@-8 {{private}}
+//   thread_local SecretDestructor sd4;   // expected-error@-8 {{private}}
+// }
+#endif
+
+[[clang::always_destroy]] SecretDestructor sd6; // expected-error{{private}}
+[[clang::always_destroy]] thread_local SecretDestructor sd7; // expected-error{{private}}
+
+[[clang::no_destroy]] SecretDestructor sd8;
+
+int main() {
+  [[clang::no_destroy]] int p; // expected-error{{no_destroy attribute can only be applied to a variable with static or thread storage duration}}
+  [[clang::always_destroy]] int p2; // expected-error{{always_destroy attribute can only be applied to a variable with static or thread storage duration}}
+  [[clang::no_destroy]] static int p3;
+  [[clang::always_destroy]] static int p4;
+}
+
+[[clang::always_destroy]] [[clang::no_destroy]] int p; // expected-error{{'no_destroy' and 'always_destroy' attributes are not compatible}} // expected-note{{here}}
+[[clang::no_destroy]] [[clang::always_destroy]] int p2; // expected-error{{'always_destroy' and 'no_destroy' attributes are not compatible}} // expected-note{{here}}

cfe/trunk/test/SemaCXX/warn-exit-time-destructors.cpp

class D {
     ~D() = default;
   };
   struct E : D {
     D d;
     ~E() = default;
   };
   E e;
 }
+
+namespace test4 {
+struct A { ~A(); };
+[[clang::no_destroy]] A a; // no warning
+}