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
17namespace clang {
18namespace clangd {
19
20namespace {
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
26class VolatileFileSystem : public llvm::vfs::ProxyFileSystem {
27public:
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(Out&: 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: Path);
42 if (FileName.starts_with(Prefix: "preamble-") && FileName.ends_with(Suffix: ".pch"))
43 return File;
44 return std::make_unique<VolatileFile>(args: std::move(*File));
45 }
46
47private:
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 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
74llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
75ThreadsafeFS::view(PathRef CWD) const {
76 auto FS = view(CWD: std::nullopt);
77 if (auto EC = FS->setCurrentWorkingDirectory(CWD))
78 elog(Fmt: "VFS: failed to set CWD to {0}: {1}", Vals&: CWD, Vals: EC.message());
79 return FS;
80}
81
82llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
83RealThreadsafeFS::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

source code of clang-tools-extra/clangd/support/ThreadsafeFS.cpp