This reverts commit e2a885537f11f8d9ced1c80c2c90069ab5adeb1d. Build failures were fixed right away and reverting the original commit without the fixes breaks the build again.
The `DiagnosticOptions` class is currently intrusively
reference-counted, which makes reasoning about its lifetime very
difficult in some cases. For example, `CompilerInvocation` owns the
`DiagnosticOptions` instance (wrapped in `llvm::IntrusiveRefCntPtr`) and
only exposes an accessor returning `DiagnosticOptions &`. One would
think this gives `CompilerInvocation` exclusive ownership of the object,
but that's not the case:
```c++
void shareOwnership(CompilerInvocation &CI) {
llvm::IntrusiveRefCntPtr<DiagnosticOptions> CoOwner = &CI.getDiagnosticOptions();
// ...
}
```
This is a perfectly valid pattern that is being actually used in the
codebase.
I would like to ensure the ownership of `DiagnosticOptions` by
`CompilerInvocation` is guaranteed to be exclusive. This can be
leveraged for a copy-on-write optimization later on. This PR changes
usages of `DiagnosticOptions` across `clang`, `clang-tools-extra` and
`lldb` to not be intrusively reference-counted.
Starting with 41e3919ded78d8870f7c95e9181c7f7e29aa3cc4 DiagnosticsEngine
creation might perform IO. It was implicitly defaulting to
getRealFileSystem. This patch makes it explicit by pushing the decision
making to callers.
It uses ambient VFS if one is available, and keeps using
`getRealFileSystem` if there aren't any VFS.
Fix a couple of issues with the handling of the current working directory in ASTUnit:
- Use `createPhysicalFileSystem` instead of `getRealFileSystem` to avoid affecting the process' current working directory, and set it at the top of `ASTUnit::LoadFromCommandLine` such that the driver used for argument parsing and the ASTUnit share the same VFS. This ensures that '-working-directory' correctly sets the VFS working directory in addition to the FileManager working directory.
- Ensure we preserve the FileSystemOptions set on the FileManager when re-creating it (as `ASTUnit::Reparse` will clear the currently set FileManager).
rdar://110697657
Reviewed By: bnbarham, benlangmuir
Differential Revision: https://reviews.llvm.org/D154134
