Implement __attribute__((internal_linkage)).

The attrubite is applicable to functions and variables and changes the linkage of the subject to internal. This is the same functionality as C-style "static", but applicable to class methods; and the same as anonymouns namespaces, but can apply to individual methods of a class. Following the proposal in http://lists.llvm.org/pipermail/cfe-dev/2015-October/045580.html llvm-svn: 252648
llvm · Nov 10, 2015 · ae6ebd3 · ae6ebd3
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diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
@@ -2132,3 +2132,9 @@ def OMPThreadPrivateDecl : InheritableAttr {
   let SemaHandler = 0;
   let Documentation = [Undocumented];
 }
+
+def InternalLinkage : InheritableAttr {
+  let Spellings = [GNU<"internal_linkage">, CXX11<"clang", "internal_linkage">];
+  let Subjects = SubjectList<[Var, Function, CXXRecord]>;
+  let Documentation = [InternalLinkageDocs];
+}
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
@@ -1666,6 +1666,15 @@ Marking virtual functions as ``not_tail_called`` is an error:
       // not_tail_called on a virtual function is an error.
       [[clang::not_tail_called]] int foo2() override;
     };
+  }];
+}
 
+def InternalLinkageDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``internal_linkage`` attribute changes the linkage type of the declaration to internal.
+This is similar to C-style ``static``, but can be used on classes and class methods. When applied to a class definition,
+this attribute affects all methods and static data members of that class.
+This can be used to contain the ABI of a C++ library by excluding unwanted class methods from the export tables.
   }];
 }
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -4085,6 +4085,12 @@ def warn_undefined_inline : Warning<"inline function %q0 is not defined">,
   InGroup<DiagGroup<"undefined-inline">>;
 def note_used_here : Note<"used here">;
 
+def err_internal_linkage_redeclaration : Error<
+  "'internal_linkage' attribute does not appear on the first declaration of %0">;
+def warn_internal_linkage_local_storage : Warning<
+  "'internal_linkage' attribute on a non-static local variable is ignored">,
+  InGroup<IgnoredAttributes>;
+
 def ext_internal_in_extern_inline : ExtWarn<
   "static %select{function|variable}0 %1 is used in an inline function with "
   "external linkage">, InGroup<StaticInInline>;

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
@@ -2115,6 +2115,11 @@ class Sema {
                                 unsigned AttrSpellingListIndex);
   OptimizeNoneAttr *mergeOptimizeNoneAttr(Decl *D, SourceRange Range,
                                           unsigned AttrSpellingListIndex);
+  InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D, SourceRange Range,
+                                                IdentifierInfo *Ident,
+                                                unsigned AttrSpellingListIndex);
+  CommonAttr *mergeCommonAttr(Decl *D, SourceRange Range, IdentifierInfo *Ident,
+                              unsigned AttrSpellingListIndex);
 
   void mergeDeclAttributes(NamedDecl *New, Decl *Old,
                            AvailabilityMergeKind AMK = AMK_Redeclaration);

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
@@ -1217,6 +1217,10 @@ getOutermostEnclosingLambda(const CXXRecordDecl *Record) {
 
 static LinkageInfo computeLVForDecl(const NamedDecl *D,
                                     LVComputationKind computation) {
+  // Internal_linkage attribute overrides other considerations.
+  if (D->hasAttr<InternalLinkageAttr>())
+    return LinkageInfo::internal();
+
   // Objective-C: treat all Objective-C declarations as having external
   // linkage.
   switch (D->getKind()) {
@@ -1307,6 +1311,10 @@ class LinkageComputer {
 public:
   static LinkageInfo getLVForDecl(const NamedDecl *D,
                                   LVComputationKind computation) {
+    // Internal_linkage attribute overrides other considerations.
+    if (D->hasAttr<InternalLinkageAttr>())
+      return LinkageInfo::internal();
+
     if (computation == LVForLinkageOnly && D->hasCachedLinkage())
       return LinkageInfo(D->getCachedLinkage(), DefaultVisibility, false);
 

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
@@ -2216,6 +2216,15 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
     NewAttr = S.mergeMinSizeAttr(D, MA->getRange(), AttrSpellingListIndex);
   else if (const auto *OA = dyn_cast<OptimizeNoneAttr>(Attr))
     NewAttr = S.mergeOptimizeNoneAttr(D, OA->getRange(), AttrSpellingListIndex);
+  else if (const auto *InternalLinkageA = dyn_cast<InternalLinkageAttr>(Attr))
+    NewAttr = S.mergeInternalLinkageAttr(
+        D, InternalLinkageA->getRange(),
+        &S.Context.Idents.get(InternalLinkageA->getSpelling()),
+        AttrSpellingListIndex);
+  else if (const auto *CommonA = dyn_cast<CommonAttr>(Attr))
+    NewAttr = S.mergeCommonAttr(D, CommonA->getRange(),
+                                &S.Context.Idents.get(CommonA->getSpelling()),
+                                AttrSpellingListIndex);
   else if (isa<AlignedAttr>(Attr))
     // AlignedAttrs are handled separately, because we need to handle all
     // such attributes on a declaration at the same time.
@@ -2664,6 +2673,13 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD,
     }
   }
 
+  if (New->hasAttr<InternalLinkageAttr>() &&
+      !Old->hasAttr<InternalLinkageAttr>()) {
+    Diag(New->getLocation(), diag::err_internal_linkage_redeclaration)
+        << New->getDeclName();
+    Diag(Old->getLocation(), diag::note_previous_definition);
+    New->dropAttr<InternalLinkageAttr>();
+  }
 
   // If a function is first declared with a calling convention, but is later
   // declared or defined without one, all following decls assume the calling
@@ -3377,6 +3393,14 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
     New->dropAttr<WeakImportAttr>();
   }
 
+  if (New->hasAttr<InternalLinkageAttr>() &&
+      !Old->hasAttr<InternalLinkageAttr>()) {
+    Diag(New->getLocation(), diag::err_internal_linkage_redeclaration)
+        << New->getDeclName();
+    Diag(Old->getLocation(), diag::note_previous_definition);
+    New->dropAttr<InternalLinkageAttr>();
+  }
+
   // Merge the types.
   VarDecl *MostRecent = Old->getMostRecentDecl();
   if (MostRecent != Old) {

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -244,11 +244,12 @@ static bool checkUInt32Argument(Sema &S, const AttributeList &Attr,
 /// \brief Diagnose mutually exclusive attributes when present on a given
 /// declaration. Returns true if diagnosed.
 template <typename AttrTy>
-static bool checkAttrMutualExclusion(Sema &S, Decl *D,
-                                     const AttributeList &Attr) {
+static bool checkAttrMutualExclusion(Sema &S, Decl *D, SourceRange Range,
+                                     IdentifierInfo *Ident) {
   if (AttrTy *A = D->getAttr<AttrTy>()) {
-    S.Diag(Attr.getLoc(), diag::err_attributes_are_not_compatible)
-      << Attr.getName() << A;
+    S.Diag(Range.getBegin(), diag::err_attributes_are_not_compatible) << Ident
+                                                                      << A;
+    S.Diag(A->getLocation(), diag::note_conflicting_attribute);
     return true;
   }
   return false;
@@ -1523,15 +1524,15 @@ static void handleAliasAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 }
 
 static void handleColdAttr(Sema &S, Decl *D, const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<HotAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<HotAttr>(S, D, Attr.getRange(), Attr.getName()))
     return;
 
   D->addAttr(::new (S.Context) ColdAttr(Attr.getRange(), S.Context,
                                         Attr.getAttributeSpellingListIndex()));
 }
 
 static void handleHotAttr(Sema &S, Decl *D, const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<ColdAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<ColdAttr>(S, D, Attr.getRange(), Attr.getName()))
     return;
 
   D->addAttr(::new (S.Context) HotAttr(Attr.getRange(), S.Context,
@@ -1573,12 +1574,13 @@ static void handleRestrictAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 static void handleCommonAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   if (S.LangOpts.CPlusPlus) {
     S.Diag(Attr.getLoc(), diag::err_attribute_not_supported_in_lang)
-      << Attr.getName() << AttributeLangSupport::Cpp;
+        << Attr.getName() << AttributeLangSupport::Cpp;
     return;
   }
 
-  D->addAttr(::new (S.Context) CommonAttr(Attr.getRange(), S.Context,
-                                        Attr.getAttributeSpellingListIndex()));
+  if (CommonAttr *CA = S.mergeCommonAttr(D, Attr.getRange(), Attr.getName(),
+                                         Attr.getAttributeSpellingListIndex()))
+    D->addAttr(CA);
 }
 
 static void handleNoReturnAttr(Sema &S, Decl *D, const AttributeList &attr) {
@@ -1703,7 +1705,8 @@ static void handleDependencyAttr(Sema &S, Scope *Scope, Decl *D,
 
 static void handleNotTailCalledAttr(Sema &S, Decl *D,
                                     const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<AlwaysInlineAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<AlwaysInlineAttr>(S, D, Attr.getRange(),
+                                                 Attr.getName()))
     return;
 
   D->addAttr(::new (S.Context) NotTailCalledAttr(
@@ -3392,6 +3395,42 @@ AlwaysInlineAttr *Sema::mergeAlwaysInlineAttr(Decl *D, SourceRange Range,
                                           AttrSpellingListIndex);
 }
 
+CommonAttr *Sema::mergeCommonAttr(Decl *D, SourceRange Range,
+                                  IdentifierInfo *Ident,
+                                  unsigned AttrSpellingListIndex) {
+  if (checkAttrMutualExclusion<InternalLinkageAttr>(*this, D, Range, Ident))
+    return nullptr;
+
+  return ::new (Context) CommonAttr(Range, Context, AttrSpellingListIndex);
+}
+
+InternalLinkageAttr *
+Sema::mergeInternalLinkageAttr(Decl *D, SourceRange Range,
+                               IdentifierInfo *Ident,
+                               unsigned AttrSpellingListIndex) {
+  if (auto VD = dyn_cast<VarDecl>(D)) {
+    // Attribute applies to Var but not any subclass of it (like ParmVar,
+    // ImplicitParm or VarTemplateSpecialization).
+    if (VD->getKind() != Decl::Var) {
+      Diag(Range.getBegin(), diag::warn_attribute_wrong_decl_type)
+          << Ident << (getLangOpts().CPlusPlus ? ExpectedFunctionVariableOrClass
+                                               : ExpectedVariableOrFunction);
+      return nullptr;
+    }
+    // Attribute does not apply to non-static local variables.
+    if (VD->hasLocalStorage()) {
+      Diag(VD->getLocation(), diag::warn_internal_linkage_local_storage);
+      return nullptr;
+    }
+  }
+
+  if (checkAttrMutualExclusion<CommonAttr>(*this, D, Range, Ident))
+    return nullptr;
+
+  return ::new (Context)
+      InternalLinkageAttr(Range, Context, AttrSpellingListIndex);
+}
+
 MinSizeAttr *Sema::mergeMinSizeAttr(Decl *D, SourceRange Range,
                                     unsigned AttrSpellingListIndex) {
   if (OptimizeNoneAttr *Optnone = D->getAttr<OptimizeNoneAttr>()) {
@@ -3428,7 +3467,8 @@ OptimizeNoneAttr *Sema::mergeOptimizeNoneAttr(Decl *D, SourceRange Range,
 
 static void handleAlwaysInlineAttr(Sema &S, Decl *D,
                                    const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<NotTailCalledAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<NotTailCalledAttr>(S, D, Attr.getRange(),
+                                                  Attr.getName()))
     return;
 
   if (AlwaysInlineAttr *Inline = S.mergeAlwaysInlineAttr(
@@ -4014,7 +4054,8 @@ static void handleObjCRequiresSuperAttr(Sema &S, Decl *D,
 
 static void handleCFAuditedTransferAttr(Sema &S, Decl *D,
                                         const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<CFUnknownTransferAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<CFUnknownTransferAttr>(S, D, Attr.getRange(),
+                                                      Attr.getName()))
     return;
 
   D->addAttr(::new (S.Context)
@@ -4024,7 +4065,8 @@ static void handleCFAuditedTransferAttr(Sema &S, Decl *D,
 
 static void handleCFUnknownTransferAttr(Sema &S, Decl *D,
                                         const AttributeList &Attr) {
-  if (checkAttrMutualExclusion<CFAuditedTransferAttr>(S, D, Attr))
+  if (checkAttrMutualExclusion<CFAuditedTransferAttr>(S, D, Attr.getRange(),
+                                                      Attr.getName()))
     return;
 
   D->addAttr(::new (S.Context)
@@ -4646,6 +4688,14 @@ static void handleNoSanitizeSpecificAttr(Sema &S, Decl *D,
                                 Attr.getAttributeSpellingListIndex()));
 }
 
+static void handleInternalLinkageAttr(Sema &S, Decl *D,
+                                      const AttributeList &Attr) {
+  if (InternalLinkageAttr *Internal =
+          S.mergeInternalLinkageAttr(D, Attr.getRange(), Attr.getName(),
+                                     Attr.getAttributeSpellingListIndex()))
+    D->addAttr(Internal);
+}
+
 /// Handles semantic checking for features that are common to all attributes,
 /// such as checking whether a parameter was properly specified, or the correct
 /// number of arguments were passed, etc.
@@ -5090,6 +5140,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case AttributeList::AT_OpenCLImageAccess:
     handleSimpleAttribute<OpenCLImageAccessAttr>(S, D, Attr);
     break;
+  case AttributeList::AT_InternalLinkage:
+    handleInternalLinkageAttr(S, D, Attr);
+    break;
 
   // Microsoft attributes:
   case AttributeList::AT_MSNoVTable:

diff --git a/clang/test/CodeGenCXX/attribute_internal_linkage.cpp b/clang/test/CodeGenCXX/attribute_internal_linkage.cpp
@@ -0,0 +1,79 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -std=c++11 -emit-llvm -o - %s | FileCheck %s
+
+__attribute__((internal_linkage)) void f() {}
+// CHECK-DAG: define internal void @_ZL1fv
+
+class A {
+public:
+  static int y __attribute__((internal_linkage));
+  static int y2 [[clang::internal_linkage]];
+// CHECK-DAG: @_ZN1A1yE = internal global
+// CHECK-DAG: @_ZN1A2y2E = internal global
+  void f1() __attribute__((internal_linkage));
+// CHECK-DAG: define internal void @_ZN1A2f1Ev
+  void f2() __attribute__((internal_linkage)) {}
+// CHECK-DAG: define internal void @_ZN1A2f2Ev
+  static void f4() __attribute__((internal_linkage)) {}
+// CHECK-DAG: define internal void @_ZN1A2f4Ev
+  A() __attribute__((internal_linkage)) {}
+// CHECK-DAG: define internal void @_ZN1AC1Ev
+// CHECK-DAG: define internal void @_ZN1AC2Ev
+  ~A() __attribute__((internal_linkage)) {}
+// CHECK-DAG: define internal void @_ZN1AD1Ev
+// CHECK-DAG: define internal void @_ZN1AD2Ev
+};
+
+int A::y;
+int A::y2;
+
+void A::f1() {
+}
+
+// Forward declaration w/o an attribute.
+class B;
+
+// Internal_linkage on a class affects all its members.
+class __attribute__((internal_linkage)) B {
+public:
+  B() {}
+  // CHECK-DAG: define internal void @_ZNL1BC1Ev
+  // CHECK-DAG: define internal void @_ZNL1BC2Ev
+  ~B() {}
+  // CHECK-DAG: define internal void @_ZNL1BD1Ev
+  // CHECK-DAG: define internal void @_ZNL1BD2Ev
+  void f() {};
+  // CHECK-DAG: define internal void @_ZNL1B1fEv
+  static int x;
+  // CHECK-DAG: @_ZNL1B1xE = internal global
+};
+
+int B::x;
+
+// Forward declaration with the attribute.
+class __attribute__((internal_linkage)) C;
+class C {
+public:
+  static int x;
+  // CHECK-DAG: @_ZNL1C1xE = internal global
+};
+
+int C::x;
+
+__attribute__((internal_linkage)) void g();
+void g() {}
+// CHECK-DAG: define internal void @_ZL1gv()
+
+void use() {
+  A a;
+  a.f1();
+  a.f2();
+  A::f4();
+  f();
+  int &Y = A::y;
+  int &Y2 = A::y2;
+  B b;
+  b.f();
+  int &XX2 = B::x;
+  g();
+  int &XX3 = C::x;
+}
diff --git a/clang/test/Sema/attr-coldhot.c b/clang/test/Sema/attr-coldhot.c
@@ -6,5 +6,7 @@ int bar() __attribute__((__cold__));
 int var1 __attribute__((__cold__)); // expected-warning{{'__cold__' attribute only applies to functions}}
 int var2 __attribute__((__hot__)); // expected-warning{{'__hot__' attribute only applies to functions}}
 
-int qux() __attribute__((__hot__)) __attribute__((__cold__)); // expected-error{{'__hot__' and 'cold' attributes are not compatible}}
-int baz() __attribute__((__cold__)) __attribute__((__hot__)); // expected-error{{'__cold__' and 'hot' attributes are not compatible}}
+int qux() __attribute__((__hot__)) __attribute__((__cold__)); // expected-error{{'__hot__' and 'cold' attributes are not compatible}} \
+// expected-note{{conflicting attribute is here}}
+int baz() __attribute__((__cold__)) __attribute__((__hot__)); // expected-error{{'__cold__' and 'hot' attributes are not compatible}} \
+// expected-note{{conflicting attribute is here}}
diff --git a/clang/test/Sema/attr-notail.c b/clang/test/Sema/attr-notail.c
@@ -1,7 +1,9 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-int callee0() __attribute__((not_tail_called,always_inline)); // expected-error{{'not_tail_called' and 'always_inline' attributes are not compatible}}
-int callee1() __attribute__((always_inline,not_tail_called)); // expected-error{{'always_inline' and 'not_tail_called' attributes are not compatible}}
+int callee0() __attribute__((not_tail_called,always_inline)); // expected-error{{'not_tail_called' and 'always_inline' attributes are not compatible}} \
+// expected-note{{conflicting attribute is here}}
+int callee1() __attribute__((always_inline,not_tail_called)); // expected-error{{'always_inline' and 'not_tail_called' attributes are not compatible}} \
+// expected-note{{conflicting attribute is here}}
 
 int foo(int a) {
   return a ? callee0() : callee1();