From 6aa64750e81b5cae9c03a0a3ed46033cda125718 Mon Sep 17 00:00:00 2001
From: Naveen Seth Hanig <naveen.hanig@outlook.com>
Date: Sat, 13 Dec 2025 18:07:49 +0100
Subject: [PATCH] [clang][DependencyScanning] Unify initVFS helpers to return
 OverlayFileSystem (NFC)

This patch is part of a series of splitting the work from #169964 into
smaller changes (see comment linked below).

The PR extends the regular and by-name dependency scanning APIs to
allow the VFS to be initialized via the initVFS helpers before
invoking the scanning APIs, with the resulting overlay filesystem
passed into the worker.

To make the API consistent, this patch updates both helpers to return
an OverlayFileSystem.

https://github.com/llvm/llvm-project/pull/169964#pullrequestreview-3545879529
---
 .../clang/DependencyScanning/DependencyScannerImpl.h       | 3 ++-
 clang/lib/DependencyScanning/DependencyScannerImpl.cpp     | 7 +++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/clang/include/clang/DependencyScanning/DependencyScannerImpl.h b/clang/include/clang/DependencyScanning/DependencyScannerImpl.h
index 9e23c0f87f273..f43c7f70183fd 100644
--- a/clang/include/clang/DependencyScanning/DependencyScannerImpl.h
+++ b/clang/include/clang/DependencyScanning/DependencyScannerImpl.h
@@ -98,7 +98,8 @@ std::unique_ptr<CompilerInvocation>
 createCompilerInvocation(ArrayRef<std::string> CommandLine,
                          DiagnosticsEngine &Diags);
 
-std::pair<IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::vector<std::string>>
+std::pair<IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem>,
+          std::vector<std::string>>
 initVFSForTUBufferScanning(IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
                            ArrayRef<std::string> CommandLine,
                            StringRef WorkingDirectory,
diff --git a/clang/lib/DependencyScanning/DependencyScannerImpl.cpp b/clang/lib/DependencyScanning/DependencyScannerImpl.cpp
index 191ffabeea4f2..201230d7d6a8e 100644
--- a/clang/lib/DependencyScanning/DependencyScannerImpl.cpp
+++ b/clang/lib/DependencyScanning/DependencyScannerImpl.cpp
@@ -430,7 +430,8 @@ dependencies::createCompilerInvocation(ArrayRef<std::string> CommandLine,
   return Invocation;
 }
 
-std::pair<IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::vector<std::string>>
+std::pair<IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem>,
+          std::vector<std::string>>
 dependencies::initVFSForTUBufferScanning(
     IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
     ArrayRef<std::string> CommandLine, StringRef WorkingDirectory,
@@ -438,7 +439,6 @@ dependencies::initVFSForTUBufferScanning(
   // Reset what might have been modified in the previous worker invocation.
   BaseFS->setCurrentWorkingDirectory(WorkingDirectory);
 
-  IntrusiveRefCntPtr<llvm::vfs::FileSystem> ModifiedFS;
   auto OverlayFS =
       llvm::makeIntrusiveRefCnt<llvm::vfs::OverlayFileSystem>(BaseFS);
   auto InMemoryFS = llvm::makeIntrusiveRefCnt<llvm::vfs::InMemoryFileSystem>();
@@ -449,11 +449,10 @@ dependencies::initVFSForTUBufferScanning(
   IntrusiveRefCntPtr<llvm::vfs::FileSystem> InMemoryOverlay = InMemoryFS;
 
   OverlayFS->pushOverlay(InMemoryOverlay);
-  ModifiedFS = OverlayFS;
   std::vector<std::string> ModifiedCommandLine(CommandLine);
   ModifiedCommandLine.emplace_back(InputPath);
 
-  return std::make_pair(ModifiedFS, ModifiedCommandLine);
+  return std::make_pair(OverlayFS, ModifiedCommandLine);
 }
 
 std::pair<IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem>,