1 //===--- ThreadsafeFS.cpp -------------------------------------------------===//
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 "support/ThreadsafeFS.h"
10 #include "Logger.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:
VolatileFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> FS)28 explicit VolatileFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> FS)
29 : ProxyFileSystem(std::move(FS)) {}
30
31 llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
openFileForRead(const llvm::Twine & InPath)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.starts_with("preamble-") && FileName.ends_with(".pch"))
43 return File;
44 return std::make_unique<VolatileFile>(std::move(*File));
45 }
46
47 private:
48 class VolatileFile : public llvm::vfs::File {
49 public:
VolatileFile(std::unique_ptr<llvm::vfs::File> Wrapped)50 VolatileFile(std::unique_ptr<llvm::vfs::File> Wrapped)
51 : Wrapped(std::move(Wrapped)) {
52 assert(this->Wrapped);
53 }
54
55 llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
getBuffer(const llvm::Twine & Name,int64_t FileSize,bool RequiresNullTerminator,bool)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
status()62 llvm::ErrorOr<llvm::vfs::Status> status() override {
63 return Wrapped->status();
64 }
getName()65 llvm::ErrorOr<std::string> getName() override { return Wrapped->getName(); }
close()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>
view(PathRef CWD) const75 ThreadsafeFS::view(PathRef CWD) const {
76 auto FS = view(std::nullopt);
77 if (auto EC = FS->setCurrentWorkingDirectory(CWD))
78 elog("VFS: failed to set CWD to {0}: {1}", CWD, EC.message());
79 return FS;
80 }
81
82 llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
viewImpl() const83 RealThreadsafeFS::viewImpl() const {
84 // Avoid using memory-mapped files.
85 // FIXME: Try to use a similar approach in Sema instead of relying on
86 // propagation of the 'isVolatile' flag through all layers.
87 return new VolatileFileSystem(llvm::vfs::createPhysicalFileSystem());
88 }
89 } // namespace clangd
90 } // namespace clang
91