Stop leaking std::strings in GetDwarfFile.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109746 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCDwarf.h

@@ -16,7 +16,7 @@
 #ifndef LLVM_MC_MCDWARF_H
 #define LLVM_MC_MCDWARF_H
 
-#include <string>
+#include "llvm/ADT/StringRef.h"
 
 namespace llvm {
   class MCContext;
@@ -29,21 +29,22 @@ namespace llvm {
   /// index 0 is not used and not a valid dwarf file number).
   class MCDwarfFile {
     // Name - the base name of the file without its directory path.
-    std::string Name;
+    // The StringRef references memory allocated in the MCContext.
+    StringRef Name;
 
     // DirIndex - the index into the list of directory names for this file name.
     unsigned DirIndex;
 
   private:  // MCContext creates and uniques these.
     friend class MCContext;
-    MCDwarfFile(std::string name, unsigned dirIndex)
+    MCDwarfFile(StringRef name, unsigned dirIndex)
       : Name(name), DirIndex(dirIndex) {}
 
     MCDwarfFile(const MCDwarfFile&);       // DO NOT IMPLEMENT
     void operator=(const MCDwarfFile&); // DO NOT IMPLEMENT
   public:
     /// getName - Get the base name of this MCDwarfFile.
-    std::string getName() const { return Name; }
+    StringRef getName() const { return Name; }
 
     /// print - Print the value to the stream \arg OS.
     void print(raw_ostream &OS) const;