isBuiltinFunc() uses StringRef instead of const char*

[gchatelet]

Summary

This prevents a bug when passing nullptr, StringRef ctor would call strlen(nullptr).
This should fix 98f3151a7dded8838fafcb5f46e6c8358def96b8 breaking sanitizer-x86_64-linux-bootstrap-msan.

[vlad.tsyrklevich]

Fix LGTM.

clang/include/clang/Basic/Builtins.h

public:
   }
 
   /// Return real builtin ID (i.e. ID it would have during compilation
   /// for AuxTarget).
   unsigned getAuxBuiltinID(unsigned ID) const { return ID - TSRecords.size(); }
 
   /// Returns true if this is a libc/libm function without the '__builtin_'
   /// prefix.
-  static bool isBuiltinFunc(const char *Name);
+  static bool isBuiltinFunc(llvm::StringRef Name);
 
   /// Returns true if this is a builtin that can be redeclared.  Returns true
   /// for non-builtins.
   bool canBeRedeclared(unsigned ID) const;
 
 private:
   const Info &getRecord(unsigned ID) const;
 

clang/lib/Basic/Builtins.cpp

 void Builtin::Context::InitializeTarget(const TargetInfo &Target,
                                         const TargetInfo *AuxTarget) {
   assert(TSRecords.empty() && "Already initialized target?");
   TSRecords = Target.getTargetBuiltins();
   if (AuxTarget)
     AuxTSRecords = AuxTarget->getTargetBuiltins();
 }
 
-bool Builtin::Context::isBuiltinFunc(const char *Name) {
-  StringRef FuncName(Name);
+bool Builtin::Context::isBuiltinFunc(llvm::StringRef FuncName) {
   for (unsigned i = Builtin::NotBuiltin + 1; i != Builtin::FirstTSBuiltin; ++i)
     if (FuncName.equals(BuiltinInfo[i].Name))
       return strchr(BuiltinInfo[i].Attributes, 'f') != nullptr;
 
   return false;
 }
 
 bool Builtin::Context::builtinIsSupported(const Builtin::Info &BuiltinInfo,

clang/lib/Sema/SemaDeclAttr.cpp

if (AL.getNumArgs() == 0)
     AddBuiltinName(kWildcard);
   else
     for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
       StringRef BuiltinName;
       SourceLocation LiteralLoc;
       if (!S.checkStringLiteralArgumentAttr(AL, I, BuiltinName, &LiteralLoc))
         return;
 
-      if (Builtin::Context::isBuiltinFunc(BuiltinName.data()))
+      if (Builtin::Context::isBuiltinFunc(BuiltinName))
         AddBuiltinName(BuiltinName);
       else
         S.Diag(LiteralLoc, diag::warn_attribute_no_builtin_invalid_builtin_name)
             << BuiltinName << AL.getAttrName()->getName();
     }
 
   // Repeating the same attribute is fine.
   llvm::sort(Names);