File descriptor leaks on header files that contain errors

[JeanYves]

Summary

When using qtcreator, I remarked that there were some file descriptor leaks inside the clang lib.
On windows OS, it is quite annoying as some files cannot be saved.

I already posted a message on this matter earlier this year:
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20151123/143910.html

[erikjv]

That's actually working around the real problem, see https://reviews.llvm.org/D27810 . I'm also not sure if this is safe: if the memory buffer is mmap-backed, this could lead to some kind of use-after-free, because clang often uses StringRefs back into buffers in order to minimise string copies.

[milianw]

Can this be abandoned now that the issue Erik has mentioned got fixed?

include/clang/Basic/FileManager.h

 /// descriptor for the file.
 class FileEntry {
   friend class FileManager;
+  friend class FileEntryCloser;
 
   StringRef Name;             // Name of the file.
   std::string RealPathName;   // Real path to the file; could be empty.

   }
 };
 
+class FileEntryCloser
+{
+public:
+   FileEntryCloser(const FileEntry *File) : m_File(File) {}
+   ~FileEntryCloser()
+   {
+      if(m_File)
+         m_File->closeFile();
+   }
+
+   const FileEntry* release()
+   {
+      const FileEntry* fileEntry = m_File;
+      m_File = nullptr;
+      return fileEntry;
+   }
+
+private:
+   const FileEntry *m_File;
+};
+
 struct FileData;
 
 /// \brief Implements support for file system lookup, file system caching,

lib/Lex/PPDirectives.cpp

     }
   }
 
+  FileEntryCloser fileEntryCloser(File);
+  
   // Should we enter the source file? Set to false if either the source file is
   // known to have no effect beyond its effect on module visibility -- that is,
   // if it's got an include guard that is already defined or is a modular header

   assert(FID.isValid() && "Expected valid file ID");
 
   // If all is good, enter the new file!
-  if (EnterSourceFile(FID, CurDir, FilenameTok.getLocation()))
+  if (EnterSourceFile(FID, CurDir, FilenameTok.getLocation())) {
+  fileEntryCloser.release();
     return;
+  }
 
   // Determine if we're switching to building a new submodule, and which one.
   if (auto *M = SuggestedModule.getModule()) {