From a22eda548b8e1f9362018dec194af0ca91b35da0 Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Tue, 8 Dec 2020 14:58:46 -0800
Subject: [PATCH] VFS: Return new file systems as uniquely owned when possible,
 almost NFC

Uniformly return uniquely-owned filesystems from VFS creation APIs. The
one exception is `getRealFileSystem`, which has a single instance and
needs to be shared.

This is almost NFC, except that it fixes a memory leak in
`vfs::collectVFSFromYAML()`.

Depends on https://reviews.llvm.org/D92888

Differential Revision: https://reviews.llvm.org/D92890
---
 llvm/include/llvm/Support/VirtualFileSystem.h    | 4 ++--
 llvm/lib/Support/VirtualFileSystem.cpp           | 8 ++++----
 llvm/unittests/Support/VirtualFileSystemTest.cpp | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/llvm/include/llvm/Support/VirtualFileSystem.h b/llvm/include/llvm/Support/VirtualFileSystem.h
index 714bd7e..f5290f0 100644
--- a/llvm/include/llvm/Support/VirtualFileSystem.h
+++ b/llvm/include/llvm/Support/VirtualFileSystem.h
@@ -500,7 +500,7 @@ llvm::sys::fs::UniqueID getNextVirtualUniqueID();
 
 /// Gets a \p FileSystem for a virtual file system described in YAML
 /// format.
-IntrusiveRefCntPtr<FileSystem>
+std::unique_ptr<FileSystem>
 getVFSFromYAML(std::unique_ptr<llvm::MemoryBuffer> Buffer,
                llvm::SourceMgr::DiagHandlerTy DiagHandler,
                StringRef YAMLFilePath, void *DiagContext = nullptr,
@@ -726,7 +726,7 @@ public:
 
   /// Parses \p Buffer, which is expected to be in YAML format and
   /// returns a virtual file system representing its contents.
-  static RedirectingFileSystem *
+  static std::unique_ptr<RedirectingFileSystem>
   create(std::unique_ptr<MemoryBuffer> Buffer,
          SourceMgr::DiagHandlerTy DiagHandler, StringRef YAMLFilePath,
          void *DiagContext, IntrusiveRefCntPtr<FileSystem> ExternalFS);
diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index 697383d..de24992 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -1639,7 +1639,7 @@ public:
   }
 };
 
-RedirectingFileSystem *
+std::unique_ptr<RedirectingFileSystem>
 RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
                               SourceMgr::DiagHandlerTy DiagHandler,
                               StringRef YAMLFilePath, void *DiagContext,
@@ -1679,7 +1679,7 @@ RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
   if (!P.parse(Root, FS.get()))
     return nullptr;
 
-  return FS.release();
+  return FS;
 }
 
 ErrorOr<RedirectingFileSystem::Entry *>
@@ -1861,7 +1861,7 @@ RedirectingFileSystem::getRealPath(const Twine &Path,
                                : llvm::errc::invalid_argument;
 }
 
-IntrusiveRefCntPtr<FileSystem>
+std::unique_ptr<FileSystem>
 vfs::getVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
                     SourceMgr::DiagHandlerTy DiagHandler,
                     StringRef YAMLFilePath, void *DiagContext,
@@ -1902,7 +1902,7 @@ void vfs::collectVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
                              SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
                              void *DiagContext,
                              IntrusiveRefCntPtr<FileSystem> ExternalFS) {
-  RedirectingFileSystem *VFS = RedirectingFileSystem::create(
+  std::unique_ptr<RedirectingFileSystem> VFS = RedirectingFileSystem::create(
       std::move(Buffer), DiagHandler, YAMLFilePath, DiagContext,
       std::move(ExternalFS));
   ErrorOr<RedirectingFileSystem::Entry *> RootE = VFS->lookupPath("/");
diff --git a/llvm/unittests/Support/VirtualFileSystemTest.cpp b/llvm/unittests/Support/VirtualFileSystemTest.cpp
index 4cc209d..1b574b3 100644
--- a/llvm/unittests/Support/VirtualFileSystemTest.cpp
+++ b/llvm/unittests/Support/VirtualFileSystemTest.cpp
@@ -1292,7 +1292,7 @@ public:
     ++Test->NumDiagnostics;
   }
 
-  IntrusiveRefCntPtr<vfs::FileSystem>
+  std::unique_ptr<vfs::FileSystem>
   getFromYAMLRawString(StringRef Content,
                        IntrusiveRefCntPtr<vfs::FileSystem> ExternalFS) {
     std::unique_ptr<MemoryBuffer> Buffer = MemoryBuffer::getMemBuffer(Content);
@@ -1300,7 +1300,7 @@ public:
                           ExternalFS);
   }
 
-  IntrusiveRefCntPtr<vfs::FileSystem> getFromYAMLString(
+  std::unique_ptr<vfs::FileSystem> getFromYAMLString(
       StringRef Content,
       IntrusiveRefCntPtr<vfs::FileSystem> ExternalFS = new DummyFileSystem()) {
     std::string VersionPlusContent("{\n  'version':0,\n");
-- 
2.7.4