[clang] Reuse configured VFS for chained includes

[jansvoboda11]

This PR propagates the already-configured VFS when handling chained includes, preventing unexpected use of the real FS and sandbox violations.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Jan Svoboda (jansvoboda11)

Changes

This PR propagates the already-configured VFS when handling chained includes, preventing unexpected use of the real FS and sandbox violations.

---

Full diff: https://github.com/llvm/llvm-project/pull/173288.diff

1 Files Affected:

• (modified) clang/lib/Frontend/ChainedIncludesSource.cpp (+1-1)

diff --git a/clang/lib/Frontend/ChainedIncludesSource.cpp b/clang/lib/Frontend/ChainedIncludesSource.cpp
index 049277c2df7a9..048ce03d09a3e 100644
--- a/clang/lib/Frontend/ChainedIncludesSource.cpp
+++ b/clang/lib/Frontend/ChainedIncludesSource.cpp
@@ -124,7 +124,7 @@ clang::createChainedIncludesSource(CompilerInstance &CI,
 
     auto Clang = std::make_unique<CompilerInstance>(
         std::move(CInvok), CI.getPCHContainerOperations());
-    Clang->createVirtualFileSystem();
+    Clang->setVirtualFileSystem(CI.getVirtualFileSystemPtr());
     Clang->setDiagnostics(Diags);
     Clang->setTarget(TargetInfo::CreateTargetInfo(
         Clang->getDiagnostics(), Clang->getInvocation().getTargetOpts()));

[cachemeifyoucan]

Is there an existing test case that catches this error?

[jansvoboda11]

Not a functional test, but this gets caught as sandbox violation by existing test cases.