namespace {
/// Always opens files in the underlying filesystem as "volatile", meaning they
-/// won't be memory-mapped. This avoid locking the files on Windows.
+/// won't be memory-mapped. Memory-mapping isn't desirable for clangd:
+/// - edits to the underlying files change contents MemoryBuffers owned by
+// SourceManager, breaking its invariants and leading to crashes
+/// - it locks files on windows, preventing edits
class VolatileFileSystem : public llvm::vfs::ProxyFileSystem {
public:
explicit VolatileFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> FS)
if (!File)
return File;
// Try to guess preamble files, they can be memory-mapped even on Windows as
- // clangd has exclusive access to those.
+ // clangd has exclusive access to those and nothing else should touch them.
llvm::StringRef FileName = llvm::sys::path::filename(Path);
if (FileName.startswith("preamble-") && FileName.endswith(".pch"))
return File;
llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>
clang::clangd::RealFileSystemProvider::getFileSystem() const {
-// Avoid using memory-mapped files on Windows, they cause file locking issues.
-// FIXME: Try to use a similar approach in Sema instead of relying on
-// propagation of the 'isVolatile' flag through all layers.
-#ifdef _WIN32
+ // Avoid using memory-mapped files.
+ // FIXME: Try to use a similar approach in Sema instead of relying on
+ // propagation of the 'isVolatile' flag through all layers.
return new VolatileFileSystem(
llvm::vfs::createPhysicalFileSystem().release());
-#else
- return llvm::vfs::createPhysicalFileSystem().release();
-#endif
}
} // namespace clangd
} // namespace clang