PR26111: segmentation fault with __attribute__((mode(QI))) on function declaration

[• d.zobnin.bugzilla]

Summary

Allow "mode" attribute to be applied to VarDecl, not ValueDecl (which includes FunctionDecl and EnumConstantDecl), emit an error if this attribute is used with function declarations and enum constants.

[aaron.ballman]

I think the better way to fix this is to add a Subjects line in Attr.td that limits the mode attribute to just TypedefNameDecl and VarDecl, then remove err_attr_wrong_decl entirely.

[• d.zobnin.bugzilla]

Thanks for the review! Updated the patch: added Subjects line for the attribute and removed the "err_attr_wrong_decl" diagnostics.

[aaron.ballman]

LGTM, thank you!

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

public:
 
   /// getMinRequiredArguments - Returns the minimum number of arguments
   /// needed to call this function. This may be fewer than the number of
   /// function parameters, if some of the parameters have default
   /// arguments (in C++).
   unsigned getMinRequiredArguments() const;
 
   QualType getReturnType() const {
+    assert(getType()->getAs<FunctionType>() && "Expected a FunctionType!");
     return getType()->getAs<FunctionType>()->getReturnType();
   }
 
   /// \brief Attempt to compute an informative source range covering the
   /// function return type. This may omit qualifiers and other information with
   /// limited representation in the AST.
   SourceRange getReturnTypeSourceRange() const;
 
   /// \brief Determine the type of an expression that calls this function.
   QualType getCallResultType() const {
+    assert(getType()->getAs<FunctionType>() && "Expected a FunctionType!");
     return getType()->getAs<FunctionType>()->getCallResultType(getASTContext());
   }
 
   /// \brief Returns true if this function or its return type has the
   /// warn_unused_result attribute. If the return type has the attribute and
   /// this function is a method of the return type's class, then false will be
   /// returned to avoid spurious warnings on member methods such as assignment
   /// operators.

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

let Args = [EnumArgument<"Interrupt", "InterruptType",
                             "hw4", "hw5", "eic", "eic"]
                            >];
   let ParseKind = "Interrupt";
   let Documentation = [MipsInterruptDocs];
 }
 
 def Mode : Attr {
   let Spellings = [GCC<"mode">];
+  let Subjects = SubjectList<[Var, TypedefName], ErrorDiag,
+                             "ExpectedVariableOrTypedef">;
   let Args = [IdentifierArgument<"Mode">];
   let Documentation = [Undocumented];
 }
 
 def Naked : InheritableAttr {
   let Spellings = [GCC<"naked">, Declspec<"naked">];
   let Subjects = SubjectList<[Function]>;
   let Documentation = [Undocumented];

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

 def err_mode_wrong_type : Error<
   "type of machine mode does not match type of base type">;
 def warn_vector_mode_deprecated : Warning<
   "specifying vector types with the 'mode' attribute is deprecated; "
   "use the 'vector_size' attribute instead">,
   InGroup<DeprecatedAttributes>;
 def err_complex_mode_vector_type : Error<
   "type of machine mode does not support base vector types">;
-def err_attr_wrong_decl : Error<
-  "%0 attribute invalid on this declaration, requires typedef or value">;
 def warn_attribute_nonnull_no_pointers : Warning<
   "'nonnull' attribute applied to function with no pointer arguments">,
   InGroup<IgnoredAttributes>;
 def warn_attribute_nonnull_parm_no_args : Warning<
   "'nonnull' attribute when used on parameters takes no arguments">,
   InGroup<IgnoredAttributes>;
 def warn_attribute_sentinel_named_arguments : Warning<
   "'sentinel' attribute requires named arguments">,

cfe/trunk/lib/Sema/SemaDeclAttr.cpp

static void handleModeAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   }
 
   if (!VectorSize)
     parseModeAttrArg(S, Str, DestWidth, IntegerMode, ComplexMode);
 
   QualType OldTy;
   if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D))
     OldTy = TD->getUnderlyingType();
-  else if (ValueDecl *VD = dyn_cast<ValueDecl>(D))
-    OldTy = VD->getType();
-  else {
-    S.Diag(D->getLocation(), diag::err_attr_wrong_decl)
-      << Attr.getName() << Attr.getRange();
-    return;
-  }
+  else
+    OldTy = cast<VarDecl>(D)->getType();
 
   // Base type can also be a vector type (see PR17453).
   // Distinguish between base type and base element type.
   QualType OldElemTy = OldTy;
   if (const VectorType *VT = OldTy->getAs<VectorType>())
     OldElemTy = VT->getElementType();
 
   if (!OldElemTy->getAs<BuiltinType>() && !OldElemTy->isComplexType())
if (NewTy.isNull()) {
     S.Diag(Attr.getLoc(), diag::err_mode_wrong_type);
     return;
   }
 
   // Install the new type.
   if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D))
     TD->setModedTypeSourceInfo(TD->getTypeSourceInfo(), NewTy);
   else
-    cast<ValueDecl>(D)->setType(NewTy);
+    cast<VarDecl>(D)->setType(NewTy);
 
   D->addAttr(::new (S.Context)
              ModeAttr(Attr.getRange(), S.Context, Name,
                       Attr.getAttributeSpellingListIndex()));
 }
 
 static void handleNoDebugAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {

cfe/trunk/test/Sema/attr-mode.c

 typedef struct {int i,j,k;} invalid_4 __attribute((mode(SI))); // expected-error{{mode attribute only supported for integer and floating-point types}}
 typedef float invalid_5 __attribute((mode(SI))); // expected-error{{type of machine mode does not match type of base type}}
 typedef int invalid_6 __attribute__((mode(12)));  // expected-error{{'mode' attribute requires an identifier}}
 
 typedef unsigned unwind_word __attribute((mode(unwind_word)));
 
 int **__attribute((mode(QI)))* i32;  // expected-error{{mode attribute}}
 
+__attribute__((mode(QI))) int invalid_func() { return 1; } // expected-error{{'mode' attribute only applies to variables and typedefs}}
+enum invalid_enum { A1 __attribute__((mode(QI))) }; // expected-error{{'mode' attribute only applies to variables and typedefs}}
+
 typedef _Complex double c32 __attribute((mode(SC)));
 int c32_test[sizeof(c32) == 8 ? 1 : -1];
 typedef _Complex float c64 __attribute((mode(DC)));
 
 #ifndef TEST_64BIT_PPC64 // Note, 'XC' mode is illegal for PPC64 machines.
 typedef _Complex float c80 __attribute((mode(XC)));
 #endif