clang-tools  10.0.0
FSProvider.cpp
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1 //===--- FSProvider.cpp - VFS provider for ClangdServer -------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "FSProvider.h"
10 #include "llvm/ADT/STLExtras.h"
11 #include "llvm/ADT/SmallString.h"
12 #include "llvm/ADT/StringRef.h"
13 #include "llvm/Support/Path.h"
14 #include "llvm/Support/VirtualFileSystem.h"
15 #include <memory>
16 
17 namespace clang {
18 namespace clangd {
19 
20 namespace {
21 /// Always opens files in the underlying filesystem as "volatile", meaning they
22 /// won't be memory-mapped. Memory-mapping isn't desirable for clangd:
23 /// - edits to the underlying files change contents MemoryBuffers owned by
24 // SourceManager, breaking its invariants and leading to crashes
25 /// - it locks files on windows, preventing edits
26 class VolatileFileSystem : public llvm::vfs::ProxyFileSystem {
27 public:
28  explicit VolatileFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> FS)
29  : ProxyFileSystem(std::move(FS)) {}
30 
31  llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
32  openFileForRead(const llvm::Twine &InPath) override {
33  llvm::SmallString<128> Path;
34  InPath.toVector(Path);
35 
36  auto File = getUnderlyingFS().openFileForRead(Path);
37  if (!File)
38  return File;
39  // Try to guess preamble files, they can be memory-mapped even on Windows as
40  // clangd has exclusive access to those and nothing else should touch them.
41  llvm::StringRef FileName = llvm::sys::path::filename(Path);
42  if (FileName.startswith("preamble-") && FileName.endswith(".pch"))
43  return File;
44  return std::unique_ptr<VolatileFile>(new VolatileFile(std::move(*File)));
45  }
46 
47 private:
48  class VolatileFile : public llvm::vfs::File {
49  public:
50  VolatileFile(std::unique_ptr<llvm::vfs::File> Wrapped)
51  : Wrapped(std::move(Wrapped)) {
52  assert(this->Wrapped);
53  }
54 
55  virtual llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
56  getBuffer(const llvm::Twine &Name, int64_t FileSize,
57  bool RequiresNullTerminator, bool /*IsVolatile*/) override {
58  return Wrapped->getBuffer(Name, FileSize, RequiresNullTerminator,
59  /*IsVolatile=*/true);
60  }
61 
62  llvm::ErrorOr<llvm::vfs::Status> status() override {
63  return Wrapped->status();
64  }
65  llvm::ErrorOr<std::string> getName() override { return Wrapped->getName(); }
66  std::error_code close() override { return Wrapped->close(); }
67 
68  private:
69  std::unique_ptr<File> Wrapped;
70  };
71 };
72 } // namespace
73 
74 llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
76  // Avoid using memory-mapped files.
77  // FIXME: Try to use a similar approach in Sema instead of relying on
78  // propagation of the 'isVolatile' flag through all layers.
79  return new VolatileFileSystem(
80  llvm::vfs::createPhysicalFileSystem().release());
81 }
82 } // namespace clangd
83 } // namespace clang
MockFSProvider FS
std::string Path
A typedef to represent a file path.
Definition: Path.h:20
static constexpr llvm::StringLiteral Name
PathRef FileName
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
llvm::IntrusiveRefCntPtr< llvm::vfs::FileSystem > getFileSystem() const override
Called by ClangdServer to obtain a vfs::FileSystem to be used for parsing.
Definition: FSProvider.cpp:75