[PATCH] D56545: [VFS] Allow multiple RealFileSystem instances with independent CWDs.

[Pavel Labath via Phabricator via llvm-commits]

labath added a subscriber: JDevlieghere.
labath added a comment.

The patch makes sense to me.

I wonder if instead of lambda-wrapping everything we couldn't use a pattern like this:

  Twine fixPath(const Twin &Orig, SmallVectorImpl<char> &Storage) {
    if (path_needs_fixing()) {
      fix_path(Orig, Storage);
      return Storage;
    }
    return Orig;
  }
  
  T whatever(const Twine &Path) {
    SmallString<N> Storage;
    // This is safe because the returned twine is either a copy of the input twine or a unary twine backed by the provided storage
    Twine Fixed = fixPath(Path, Storage);
    return do_stuff(Fixed);
  }

This usage of `Twine` isn't very nice, but neither is lambda-wrapping everything, so it's kind of a pick-your-poison situation. Anyway, just throwing the idea out there...



================
Comment at: lib/Support/VirtualFileSystem.cpp:241
 public:
+  RealFileSystem(bool LinkCWDToProcess) {
+    if (!LinkCWDToProcess) {
----------------
explicit


================
Comment at: lib/Support/VirtualFileSystem.cpp:265
+  template <typename Func, typename R = decltype(std::declval<Func>()(Twine()))>
+  R WithFixedPath(const Twine& Path, const Func &F) const {
+    if (!WD)
----------------
It looks like it should be possible to use the trailing return type syntax to simplify this (`auto WithFixedPath(Path, F) -> decltype(F(Path))`


Repository:
  rL LLVM

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  https://reviews.llvm.org/D56545/new/

https://reviews.llvm.org/D56545