If an object (such as a std::string) with an appropriate c_str() member function

is passed to a variadic function in a position where a format string indicates
that c_str()'s return type is desired, provide a note suggesting that the user
may have intended to call the c_str() member.

Factor the non-POD-vararg checking out of DefaultVariadicArgumentPromotion and
move it to SemaChecking in order to facilitate this. Factor the call checking
out of function call checking and block call checking, and extend it to cover
constructor calls too.

Patch by Sam Panzer!

llvm-svn: 158887

Author: zygoloid

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -4723,6 +4723,11 @@ def err_cannot_pass_objc_interface_to_vararg : Error<
   "cannot pass object with interface type %0 by-value through variadic "
   "%select{function|block|method}1">;
 
+def warn_non_pod_vararg_with_format_string : Warning<
+  "cannot pass %select{non-POD|non-trivial}0 object of type %1 to variadic "
+  "function; expected type from format string was %2">,
+  InGroup<DiagGroup<"non-pod-varargs">>, DefaultError;
+
 def warn_cannot_pass_non_pod_arg_to_vararg : Warning<
   "cannot pass object of %select{non-POD|non-trivial}0 type %1 through variadic"
   " %select{function|block|method|constructor}2; call will abort at runtime">,
@@ -5206,7 +5211,8 @@ def warn_scanf_scanlist_incomplete : Warning<
   "no closing ']' for '%%[' in scanf format string">,
   InGroup<Format>;
 def note_format_string_defined : Note<"format string is defined here">;
- 
+def note_printf_c_str: Note<"did you mean to call the %0 method?">;
+
 def warn_null_arg : Warning<
   "null passed to a callee which requires a non-null argument">,
   InGroup<NonNull>;
@@ -5666,4 +5672,3 @@ def err_module_private_definition : Error<
 }
 
 } // end of sema component.
-

clang/include/clang/Sema/Sema.h

@@ -6409,6 +6409,21 @@ class Sema {
     VariadicDoesNotApply
   };
 
+  VariadicCallType getVariadicCallType(FunctionDecl *FDecl,
+                                       const FunctionProtoType *Proto,
+                                       Expr *Fn);
+
+  // Used for determining in which context a type is allowed to be passed to a
+  // vararg function.
+  enum VarArgKind {
+    VAK_Valid,
+    VAK_ValidInCXX11,
+    VAK_Invalid
+  };
+
+  // Determines which VarArgKind fits an expression.
+  VarArgKind isValidVarArgType(const QualType &Ty);
+
   /// GatherArgumentsForCall - Collector argument expressions for various
   /// form of call prototypes.
   bool GatherArgumentsForCall(SourceLocation CallLoc,
@@ -6421,10 +6436,14 @@ class Sema {
                               bool AllowExplicit = false);
 
   // DefaultVariadicArgumentPromotion - Like DefaultArgumentPromotion, but
-  // will warn if the resulting type is not a POD type.
+  // will return ExprError() if the resulting type is not a POD type.
   ExprResult DefaultVariadicArgumentPromotion(Expr *E, VariadicCallType CT,
                                               FunctionDecl *FDecl);
 
+  /// Checks to see if the given expression is a valid argument to a variadic
+  /// function, issuing a diagnostic and returning NULL if not.
+  bool variadicArgumentPODCheck(const Expr *E, VariadicCallType CT);
+
   // UsualArithmeticConversions - performs the UsualUnaryConversions on it's
   // operands and then handles various conversions that are common to binary
   // operators (C99 6.3.1.8). If both operands aren't arithmetic, this
@@ -6999,10 +7018,33 @@ class Sema {
                         const ArraySubscriptExpr *ASE=0,
                         bool AllowOnePastEnd=true, bool IndexNegated=false);
   void CheckArrayAccess(const Expr *E);
-  bool CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall);
+  // Used to grab the relevant information from a FormatAttr and a
+  // FunctionDeclaration.
+  struct FormatStringInfo {
+    unsigned FormatIdx;
+    unsigned FirstDataArg;
+    bool HasVAListArg;
+  };
+
+  bool getFormatStringInfo(const FormatAttr *Format, bool IsCXXMember,
+                           FormatStringInfo *FSI);
+  bool CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall,
+                         const FunctionProtoType *Proto);
   bool CheckObjCMethodCall(ObjCMethodDecl *Method, SourceLocation loc, 
                            Expr **Args, unsigned NumArgs);
-  bool CheckBlockCall(NamedDecl *NDecl, CallExpr *TheCall);
+  bool CheckBlockCall(NamedDecl *NDecl, CallExpr *TheCall,
+                      const FunctionProtoType *Proto);
+  void CheckConstructorCall(FunctionDecl *FDecl,
+                            Expr **Args,
+                            unsigned NumArgs,
+                            const FunctionProtoType *Proto,
+                            SourceLocation Loc);
+
+  void checkCall(NamedDecl *FDecl, Expr **Args, unsigned NumArgs,
+                 unsigned NumProtoArgs, bool IsMemberFunction,
+                 SourceLocation Loc, SourceRange Range,
+                 VariadicCallType CallType);
+
 
   bool CheckObjCString(Expr *Arg);
 
@@ -7037,21 +7079,31 @@ class Sema {
     FST_Unknown
   };
   static FormatStringType GetFormatStringType(const FormatAttr *Format);
-  bool SemaCheckStringLiteral(const Expr *E, Expr **Args, unsigned NumArgs,
-                              bool HasVAListArg, unsigned format_idx,
-                              unsigned firstDataArg, FormatStringType Type,
-                              bool inFunctionCall = true);
+
+  enum StringLiteralCheckType {
+    SLCT_NotALiteral,
+    SLCT_UncheckedLiteral,
+    SLCT_CheckedLiteral
+  };
+
+  StringLiteralCheckType checkFormatStringExpr(const Expr *E,
+                                               Expr **Args, unsigned NumArgs,
+                                               bool HasVAListArg,
+                                               unsigned format_idx,
+                                               unsigned firstDataArg,
+                                               FormatStringType Type,
+                                               bool inFunctionCall = true);
 
   void CheckFormatString(const StringLiteral *FExpr, const Expr *OrigFormatExpr,
                          Expr **Args, unsigned NumArgs, bool HasVAListArg,
                          unsigned format_idx, unsigned firstDataArg,
                          FormatStringType Type, bool inFunctionCall);
 
-  void CheckFormatArguments(const FormatAttr *Format, CallExpr *TheCall);
-  void CheckFormatArguments(const FormatAttr *Format, Expr **Args,
+  bool CheckFormatArguments(const FormatAttr *Format, CallExpr *TheCall);
+  bool CheckFormatArguments(const FormatAttr *Format, Expr **Args,
                             unsigned NumArgs, bool IsCXXMember,
                             SourceLocation Loc, SourceRange Range);
-  void CheckFormatArguments(Expr **Args, unsigned NumArgs,
+  bool CheckFormatArguments(Expr **Args, unsigned NumArgs,
                             bool HasVAListArg, unsigned format_idx,
                             unsigned firstDataArg, FormatStringType Type,
                             SourceLocation Loc, SourceRange range);