Add lifetime categories attributes

Summary:
This is the first part of work announced in
"[RFC] Adding lifetime analysis to clang" [0],
i.e. the addition of the [[gsl::Owner(T)]] and
[[gsl::Pointer(T)]] attributes, which
will enable user-defined types to participate in
the lifetime analysis (which will be part of the
next PR).
The type `T` here is called "DerefType" in the paper,
and denotes the type that an Owner owns and a Pointer
points to. E.g. `std::vector<int>` should be annotated
with `[[gsl::Owner(int)]]` and
a `std::vector<int>::iterator` with `[[gsl::Pointer(int)]]`.

[0] http://lists.llvm.org/pipermail/cfe-dev/2018-November/060355.html

Reviewers: gribozavr

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63954

llvm-svn: 367040

clang/include/clang/Basic/Attr.td

@@ -2796,6 +2796,20 @@ def TypeTagForDatatype : InheritableAttr {
   let Documentation = [TypeTagForDatatypeDocs];
 }
 
+def Owner : InheritableAttr {
+  let Spellings = [CXX11<"gsl", "Owner">];
+  let Subjects = SubjectList<[Struct]>;
+  let Args = [TypeArgument<"DerefType", /*opt=*/1>];
+  let Documentation = [LifetimeOwnerDocs];
+}
+
+def Pointer : InheritableAttr {
+  let Spellings = [CXX11<"gsl", "Pointer">];
+  let Subjects = SubjectList<[Struct]>;
+  let Args = [TypeArgument<"DerefType", /*opt=*/1>];
+  let Documentation = [LifetimePointerDocs];
+}
+
 // Microsoft-related attributes
 
 def MSNoVTable : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {

clang/include/clang/Basic/AttrDocs.td

@@ -4230,3 +4230,71 @@ not initialized on device side. It has internal linkage and is initialized by
 the initializer on host side.
   }];
 }
+
+def LifetimeOwnerDocs : Documentation {
+  let Category = DocCatDecl;
+  let Content = [{
+.. Note:: This attribute is experimental and its effect on analysis is subject to change in
+  a future version of clang.
+
+The attribute ``[[gsl::Owner(T)]]`` applies to structs and classes that own an
+object of type ``T``:
+
+.. code-block:: c++
+
+  class [[gsl::Owner(int)]] IntOwner {
+  private:
+    int value;
+  public:
+    int *getInt() { return &value; }
+  };
+
+The argument ``T`` is optional and currently ignored.
+This attribute may be used by analysis tools and has no effect on code
+generation.
+
+See Pointer_ for an example.
+}];
+}
+
+def LifetimePointerDocs : Documentation {
+  let Category = DocCatDecl;
+  let Content = [{
+.. Note:: This attribute is experimental and its effect on analysis is subject to change in
+  a future version of clang.
+
+The attribute ``[[gsl::Pointer(T)]]`` applies to structs and classes that behave
+like pointers to an object of type ``T``:
+
+.. code-block:: c++
+
+  class [[gsl::Pointer(int)]] IntPointer {
+  private:
+    int *valuePointer;
+  public:
+    int *getInt() { return &valuePointer; }
+  };
+
+The argument ``T`` is optional and currently ignored.
+This attribute may be used by analysis tools and has no effect on code
+generation.
+
+Example:
+When constructing an instance of a class annotated like this (a Pointer) from
+an instance of a class annotated with ``[[gsl::Owner]]`` (an Owner),
+then the analysis will consider the Pointer to point inside the Owner.
+When the Owner's lifetime ends, it will consider the Pointer to be dangling.
+
+.. code-block:: c++
+
+  int f() {
+    IntPointer P;
+    if (true) {
+      IntOwner O(7);
+      P = IntPointer(O); // P "points into" O
+    } // P is dangling
+    return P.get(); // error: Using a dangling Pointer.
+  }
+
+}];
+}

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2519,6 +2519,9 @@ def err_nsobject_attribute : Error<
   "'NSObject' attribute is for pointer types only">;
 def err_attributes_are_not_compatible : Error<
   "%0 and %1 attributes are not compatible">;
+def err_attribute_invalid_argument : Error<
+  "%select{'void'|a reference type|an array type|a non-vector or "
+  "non-vectorizable scalar type}0 is an invalid argument to attribute %1">;
 def err_attribute_wrong_number_arguments : Error<
   "%0 attribute %plural{0:takes no arguments|1:takes one argument|"
   ":requires exactly %1 arguments}1">;
@@ -2567,8 +2570,6 @@ def err_attribute_argument_out_of_range : Error<
 def err_init_priority_object_attr : Error<
   "can only use 'init_priority' attribute on file-scope definitions "
   "of objects of class type">;
-def err_attribute_argument_vec_type_hint : Error<
-  "invalid attribute argument %0 - expecting a vector or vectorizable scalar type">;
 def err_attribute_argument_out_of_bounds : Error<
   "%0 attribute parameter %1 is out of bounds">;
 def err_attribute_only_once_per_parameter : Error<

clang/lib/Parse/ParseDecl.cpp

@@ -335,6 +335,7 @@ unsigned Parser::ParseAttributeArgsCommon(
   ConsumeParen();
 
   bool ChangeKWThisToIdent = attributeTreatsKeywordThisAsIdentifier(*AttrName);
+  bool AttributeIsTypeArgAttr = attributeIsTypeArgAttr(*AttrName);
 
   // Interpret "kw_this" as an identifier if the attributed requests it.
   if (ChangeKWThisToIdent && Tok.is(tok::kw_this))
@@ -360,6 +361,7 @@ unsigned Parser::ParseAttributeArgsCommon(
       ArgExprs.push_back(ParseIdentifierLoc());
   }
 
+  ParsedType TheParsedType;
   if (!ArgExprs.empty() ? Tok.is(tok::comma) : Tok.isNot(tok::r_paren)) {
     // Eat the comma.
     if (!ArgExprs.empty())
@@ -372,8 +374,17 @@ unsigned Parser::ParseAttributeArgsCommon(
         Tok.setKind(tok::identifier);
 
       ExprResult ArgExpr;
-      if (Tok.is(tok::identifier) &&
-          attributeHasVariadicIdentifierArg(*AttrName)) {
+      if (AttributeIsTypeArgAttr) {
+        TypeResult T = ParseTypeName();
+        if (T.isInvalid()) {
+          SkipUntil(tok::r_paren, StopAtSemi);
+          return 0;
+        }
+        if (T.isUsable())
+          TheParsedType = T.get();
+        break; // FIXME: Multiple type arguments are not implemented.
+      } else if (Tok.is(tok::identifier) &&
+                 attributeHasVariadicIdentifierArg(*AttrName)) {
         ArgExprs.push_back(ParseIdentifierLoc());
       } else {
         bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
@@ -397,14 +408,20 @@ unsigned Parser::ParseAttributeArgsCommon(
   SourceLocation RParen = Tok.getLocation();
   if (!ExpectAndConsume(tok::r_paren)) {
     SourceLocation AttrLoc = ScopeLoc.isValid() ? ScopeLoc : AttrNameLoc;
-    Attrs.addNew(AttrName, SourceRange(AttrLoc, RParen), ScopeName, ScopeLoc,
-                 ArgExprs.data(), ArgExprs.size(), Syntax);
+
+    if (AttributeIsTypeArgAttr && !TheParsedType.get().isNull()) {
+      Attrs.addNewTypeAttr(AttrName, SourceRange(AttrNameLoc, RParen),
+                           ScopeName, ScopeLoc, TheParsedType, Syntax);
+    } else {
+      Attrs.addNew(AttrName, SourceRange(AttrLoc, RParen), ScopeName, ScopeLoc,
+                   ArgExprs.data(), ArgExprs.size(), Syntax);
+    }
   }
 
   if (EndLoc)
     *EndLoc = RParen;
 
-  return static_cast<unsigned>(ArgExprs.size());
+  return static_cast<unsigned>(ArgExprs.size() + !TheParsedType.get().isNull());
 }
 
 /// Parse the arguments to a parameterized GNU attribute or

clang/lib/Sema/SemaDeclAttr.cpp

@@ -2954,8 +2954,7 @@ static void handleVecTypeHint(Sema &S, Decl *D, const ParsedAttr &AL) {
   if (!ParmType->isExtVectorType() && !ParmType->isFloatingType() &&
       (ParmType->isBooleanType() ||
        !ParmType->isIntegralType(S.getASTContext()))) {
-    S.Diag(AL.getLoc(), diag::err_attribute_argument_vec_type_hint)
-        << ParmType;
+    S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument) << 3 << AL;
     return;
   }
 
@@ -4555,6 +4554,67 @@ static void handleSuppressAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
       DiagnosticIdentifiers.size(), AL.getAttributeSpellingListIndex()));
 }
 
+static void handleLifetimeCategoryAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  TypeSourceInfo *DerefTypeLoc = nullptr;
+  QualType ParmType;
+  if (AL.hasParsedType()) {
+    ParmType = S.GetTypeFromParser(AL.getTypeArg(), &DerefTypeLoc);
+
+    unsigned SelectIdx = ~0U;
+    if (ParmType->isVoidType())
+      SelectIdx = 0;
+    else if (ParmType->isReferenceType())
+      SelectIdx = 1;
+    else if (ParmType->isArrayType())
+      SelectIdx = 2;
+
+    if (SelectIdx != ~0U) {
+      S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument)
+          << SelectIdx << AL;
+      return;
+    }
+  }
+
+  // To check if earlier decl attributes do not conflict the newly parsed ones
+  // we always add (and check) the attribute to the cannonical decl.
+  D = D->getCanonicalDecl();
+  if (AL.getKind() == ParsedAttr::AT_Owner) {
+    if (checkAttrMutualExclusion<PointerAttr>(S, D, AL))
+      return;
+    if (const auto *OAttr = D->getAttr<OwnerAttr>()) {
+      const Type *ExistingDerefType = OAttr->getDerefTypeLoc()
+                                          ? OAttr->getDerefType().getTypePtr()
+                                          : nullptr;
+      if (ExistingDerefType != ParmType.getTypePtrOrNull()) {
+        S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
+            << AL << OAttr;
+        S.Diag(OAttr->getLocation(), diag::note_conflicting_attribute);
+      }
+      return;
+    }
+    D->addAttr(::new (S.Context)
+                   OwnerAttr(AL.getRange(), S.Context, DerefTypeLoc,
+                             AL.getAttributeSpellingListIndex()));
+  } else {
+    if (checkAttrMutualExclusion<OwnerAttr>(S, D, AL))
+      return;
+    if (const auto *PAttr = D->getAttr<PointerAttr>()) {
+      const Type *ExistingDerefType = PAttr->getDerefTypeLoc()
+                                          ? PAttr->getDerefType().getTypePtr()
+                                          : nullptr;
+      if (ExistingDerefType != ParmType.getTypePtrOrNull()) {
+        S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
+            << AL << PAttr;
+        S.Diag(PAttr->getLocation(), diag::note_conflicting_attribute);
+      }
+      return;
+    }
+    D->addAttr(::new (S.Context)
+                   PointerAttr(AL.getRange(), S.Context, DerefTypeLoc,
+                               AL.getAttributeSpellingListIndex()));
+  }
+}
+
 bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
                                 const FunctionDecl *FD) {
   if (Attrs.isInvalid())
@@ -7158,6 +7218,10 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_Suppress:
     handleSuppressAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_Owner:
+  case ParsedAttr::AT_Pointer:
+    handleLifetimeCategoryAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_OpenCLKernel:
     handleSimpleAttribute<OpenCLKernelAttr>(S, D, AL);
     break;

clang/test/AST/ast-dump-attr.cpp

@@ -211,6 +211,23 @@ namespace TestSuppress {
     }
 }
 
+namespace TestLifetimeCategories {
+class [[gsl::Owner(int)]] AOwner{};
+// CHECK: CXXRecordDecl{{.*}} class AOwner
+// CHECK: OwnerAttr {{.*}} int
+class [[gsl::Pointer(int)]] APointer{};
+// CHECK: CXXRecordDecl{{.*}} class APointer
+// CHECK: PointerAttr {{.*}} int
+
+class [[gsl::Pointer]] PointerWithoutArgument{};
+// CHECK: CXXRecordDecl{{.*}} class PointerWithoutArgument
+// CHECK: PointerAttr
+
+class [[gsl::Owner]] OwnerWithoutArgument{};
+// CHECK: CXXRecordDecl{{.*}} class OwnerWithoutArgument
+// CHECK: OwnerAttr
+} // namespace TestLifetimeCategories
+
 // Verify the order of attributes in the Ast. It must reflect the order
 // in the parsed source.
 int mergeAttrTest() __attribute__((deprecated)) __attribute__((warn_unused_result));

clang/test/Misc/pragma-attribute-supported-attributes-list.test

@@ -117,8 +117,10 @@
 // CHECK-NEXT: OpenCLNoSVM (SubjectMatchRule_variable)
 // CHECK-NEXT: OptimizeNone (SubjectMatchRule_function, SubjectMatchRule_objc_method)
 // CHECK-NEXT: Overloadable (SubjectMatchRule_function)
+// CHECK-NEXT: Owner (SubjectMatchRule_record_not_is_union)
 // CHECK-NEXT: ParamTypestate (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: PassObjectSize (SubjectMatchRule_variable_is_parameter)
+// CHECK-NEXT: Pointer (SubjectMatchRule_record_not_is_union)
 // CHECK-NEXT: RenderScriptKernel (SubjectMatchRule_function)
 // CHECK-NEXT: ReqdWorkGroupSize (SubjectMatchRule_function)
 // CHECK-NEXT: RequireConstantInit (SubjectMatchRule_variable_is_global)