[ModuleDependencyCollector] Use llvm::sys::fs::real_path

[JDevlieghere]

Summary

Use the real_path from llvm::sys::fs::real_path instead of having a custom implementation.

[bruno]

Thanks for working on this! LGTM

clang/lib/Frontend/ModuleDependencyCollector.cpp

if (!UmbrellaDir.equals(UmbreallDirFromHeader)) {
       if (FileMgr->getFile(AltHeaderFilename))
         moduleMapAddHeader(AltHeaderFilename);
     }
   }
 };
 
 }
 
-// TODO: move this to Support/Path.h and check for HAVE_REALPATH?
-static bool real_path(StringRef SrcPath, SmallVectorImpl<char> &RealPath) {
-#ifdef LLVM_ON_UNIX
-  char CanonicalPath[PATH_MAX];
-
-  // TODO: emit a warning in case this fails...?
-  if (!realpath(SrcPath.str().c_str(), CanonicalPath))
-    return false;
-
-  SmallString<256> RPath(CanonicalPath);
-  RealPath.swap(RPath);
-  return true;
-#else
-  // FIXME: Add support for systems without realpath.
-  return false;
-#endif
-}
-
 void ModuleDependencyCollector::attachToASTReader(ASTReader &R) {
   R.addListener(llvm::make_unique<ModuleDependencyListener>(*this));
 }
 
 void ModuleDependencyCollector::attachToPreprocessor(Preprocessor &PP) {
   PP.addPPCallbacks(llvm::make_unique<ModuleDependencyPPCallbacks>(
       *this, PP.getSourceManager()));
   PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
       llvm::make_unique<ModuleDependencyMMCallbacks>(*this));
 }
 
 static bool isCaseSensitivePath(StringRef Path) {
   SmallString<256> TmpDest = Path, UpperDest, RealDest;
   // Remove component traversals, links, etc.
-  if (!real_path(Path, TmpDest))
+  if (llvm::sys::fs::real_path(Path, TmpDest))
     return true; // Current default value in vfs.yaml
   Path = TmpDest;
 
   // Change path to all upper case and ask for its real path, if the latter
   // exists and is equal to Path, it's not case sensitive. Default to case
   // sensitive in the absence of realpath, since this is what the VFSWriter
   // already expects when sensitivity isn't setup.
   for (auto &C : Path)
     UpperDest.push_back(toUppercase(C));
-  if (real_path(UpperDest, RealDest) && Path.equals(RealDest))
+  if (!llvm::sys::fs::real_path(UpperDest, RealDest) && Path.equals(RealDest))
     return false;
   return true;
 }
 
 void ModuleDependencyCollector::writeFileMap() {
   if (Seen.empty())
     return;
 
bool ModuleDependencyCollector::getRealPath(StringRef SrcPath,
   StringRef FileName = path::filename(SrcPath);
   std::string Dir = path::parent_path(SrcPath).str();
   auto DirWithSymLink = SymLinkMap.find(Dir);
 
   // Use real_path to fix any symbolic link component present in a path.
   // Computing the real path is expensive, cache the search through the
   // parent path directory.
   if (DirWithSymLink == SymLinkMap.end()) {
-    if (!real_path(Dir, RealPath))
+    if (llvm::sys::fs::real_path(Dir, RealPath))
       return false;
     SymLinkMap[Dir] = RealPath.str();
   } else {
     RealPath = DirWithSymLink->second;
   }
 
   path::append(RealPath, FileName);
   Result.swap(RealPath);