[clang] [llvm] [llvm][clang] Sandbox filesystem reads (PR #165350)

[Ben Langmuir via llvm-commits]

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@@ -399,10 +422,14 @@ void RealFileSystem::printImpl(raw_ostream &OS, PrintType Type,
 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
   static IntrusiveRefCntPtr<FileSystem> FS =
       makeIntrusiveRefCnt<RealFileSystem>(true);
+  sys::sandbox::violationIfEnabled();
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benlangmuir wrote:

We should document that this and `createPhysicalFileSystem` can only be used outside the sandbox. I think it is a bit less obvious than for the low level operations.

https://github.com/llvm/llvm-project/pull/165350