[Sema] Improve -Wstrict-prototypes diagnostic message for blocks

[ahatanak]

Summary

Currently, clang prints the same warning message "this function declaration is not a prototype" for non-prototype declarations of blocks and normal functions. This commit makes changes needed to print a more accurate warning "this block declaration is not a prototype" when the declaration is a block.

rdar://problem/32461723

[dexonsmith]

LGTM.

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

 def note_sentinel_here : Note<
   "%select{function|method|block}0 has been explicitly marked sentinel here">;
 def warn_missing_prototype : Warning<
   "no previous prototype for function %0">,
   InGroup<DiagGroup<"missing-prototypes">>, DefaultIgnore;
 def note_declaration_not_a_prototype : Note<
   "this declaration is not a prototype; add 'void' to make it a prototype for a zero-parameter function">; 
 def warn_strict_prototypes : Warning<
-  "this %select{function declaration is not|"
+  "this %select{function declaration is not|block declaration is not|"
   "old-style function definition is not preceded by}0 a prototype">,
   InGroup<DiagGroup<"strict-prototypes">>, DefaultIgnore;
 def warn_missing_variable_declarations : Warning<
   "no previous extern declaration for non-static variable %0">,
   InGroup<DiagGroup<"missing-variable-declarations">>, DefaultIgnore;
 def err_static_data_member_reinitialization :
   Error<"static data member %0 already has an initializer">;
 def err_redefinition : Error<"redefinition of %0">;

cfe/trunk/lib/Sema/SemaDecl.cpp

if (ShouldWarnAboutMissingPrototype(FD, PossibleZeroParamPrototype)) {
       //   An empty list in a function declarator that is part of a definition
       //   of that function specifies that the function has no parameters
       //   (C99 6.7.5.3p14)
       if (!FD->hasWrittenPrototype() && FD->getNumParams() > 0 &&
           !LangOpts.CPlusPlus) {
         TypeSourceInfo *TI = FD->getTypeSourceInfo();
         TypeLoc TL = TI->getTypeLoc();
         FunctionTypeLoc FTL = TL.getAsAdjusted<FunctionTypeLoc>();
-        Diag(FTL.getLParenLoc(), diag::warn_strict_prototypes) << 1;
+        Diag(FTL.getLParenLoc(), diag::warn_strict_prototypes) << 2;
       }
     }
 
     if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
       const CXXMethodDecl *KeyFunction;
       if (MD->isOutOfLine() && (MD = MD->getCanonicalDecl()) &&
           MD->isVirtual() &&
           (KeyFunction = Context.getCurrentKeyFunction(MD->getParent())) &&

cfe/trunk/lib/Sema/SemaType.cpp

case DeclaratorChunk::Function: {
             << (D.getContext() == Declarator::AliasDeclContext ||
                 D.getContext() == Declarator::AliasTemplateContext);
 
       // If we see "T var();" or "T var(T());" at block scope, it is probably
       // an attempt to initialize a variable, not a function declaration.
       if (FTI.isAmbiguous)
         warnAboutAmbiguousFunction(S, D, DeclType, T);
 
-      // GNU warning -Wstrict-prototypes
-      //   Warn if a function declaration is without a prototype.
-      //   This warning is issued for all kinds of unprototyped function
-      //   declarations (i.e. function type typedef, function pointer etc.)
-      //   C99 6.7.5.3p14:
-      //   The empty list in a function declarator that is not part of a
-      //   definition of that function specifies that no information
-      //   about the number or types of the parameters is supplied.
-      if (D.getFunctionDefinitionKind() == FDK_Declaration &&
-          FTI.NumParams == 0 && !LangOpts.CPlusPlus)
-        S.Diag(DeclType.Loc, diag::warn_strict_prototypes)
-            << 0 << FixItHint::CreateInsertion(FTI.getRParenLoc(), "void");
-
       FunctionType::ExtInfo EI(getCCForDeclaratorChunk(S, D, FTI, chunkIndex));
 
       if (!FTI.NumParams && !FTI.isVariadic && !LangOpts.CPlusPlus) {
         // Simple void foo(), where the incoming T is the result type.
         T = Context.getFunctionNoProtoType(T, EI);
       } else {
         // We allow a zero-parameter variadic function in C if the
         // function is marked with the "overloadable" attribute. Scan
if (T.isNull()) {
       T = Context.IntTy;
     }
 
     // See if there are any attributes on this declarator chunk.
     processTypeAttrs(state, T, TAL_DeclChunk,
                      const_cast<AttributeList *>(DeclType.getAttrs()));
   }
 
+  // GNU warning -Wstrict-prototypes
+  //   Warn if a function declaration is without a prototype.
+  //   This warning is issued for all kinds of unprototyped function
+  //   declarations (i.e. function type typedef, function pointer etc.)
+  //   C99 6.7.5.3p14:
+  //   The empty list in a function declarator that is not part of a definition
+  //   of that function specifies that no information about the number or types
+  //   of the parameters is supplied.
+  if (!LangOpts.CPlusPlus && D.getFunctionDefinitionKind() == FDK_Declaration) {
+    bool IsBlock = false;
+    for (const DeclaratorChunk &DeclType : D.type_objects()) {
+      switch (DeclType.Kind) {
+      case DeclaratorChunk::BlockPointer:
+        IsBlock = true;
+        break;
+      case DeclaratorChunk::Function: {
+        const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
+        if (FTI.NumParams == 0)
+          S.Diag(DeclType.Loc, diag::warn_strict_prototypes)
+              << IsBlock
+              << FixItHint::CreateInsertion(FTI.getRParenLoc(), "void");
+        IsBlock = false;
+        break;
+      }
+      default:
+        break;
+      }
+    }
+  }
+
   assert(!T.isNull() && "T must not be null after this point");
 
   if (LangOpts.CPlusPlus && T->isFunctionType()) {
     const FunctionProtoType *FnTy = T->getAs<FunctionProtoType>();
     assert(FnTy && "Why oh why is there not a FunctionProtoType here?");
 
     // C++ 8.3.5p4:
     //   A cv-qualifier-seq shall only be part of the function type

cfe/trunk/test/Sema/warn-strict-prototypes.m

 // RUN: %clang_cc1 -fsyntax-only -Wstrict-prototypes -verify -fblocks %s
 
 @interface Foo
 
-@property (nonatomic, copy) void (^noProtoBlock)(); // expected-warning {{this function declaration is not a prototype}}
+@property (nonatomic, copy) void (^noProtoBlock)(); // expected-warning {{this block declaration is not a prototype}}
 @property (nonatomic, copy) void (^block)(void); // no warning
 
-- doStuff:(void (^)()) completionHandler; // expected-warning {{this function declaration is not a prototype}}
+- doStuff:(void (^)()) completionHandler; // expected-warning {{this block declaration is not a prototype}}
 - doOtherStuff:(void (^)(void)) completionHandler; // no warning
 
 @end
 
 void foo() {
-  void (^block)() = // expected-warning {{this function declaration is not a prototype}}
+  void (^block)() = // expected-warning {{this block declaration is not a prototype}}
                     ^void(int arg) { // no warning
   };
   void (^block2)(void) = ^void() { // no warning
   };
   void (^block3)(void) = ^ { // no warning
   };
 }
+
+void (*(^(*(^block4)()) // expected-warning {{this block declaration is not a prototype}}
+     ()) // expected-warning {{this function declaration is not a prototype}}
+     ()) // expected-warning {{this block declaration is not a prototype}}
+     (); // expected-warning {{this function declaration is not a prototype}}