| commit | 9e306ad4600c4d3392c194a8be88919ee758425c | [log] [tgz] |
|---|---|---|
| author | Jan Svoboda <jan_svoboda@apple.com> | Thu May 22 12:33:52 2025 -0700 |
| committer | GitHub <noreply@github.com> | Thu May 22 12:33:52 2025 -0700 |
| tree | f8b15171e92d056e9006bcbe36d534a9d73155d9 | |
| parent | 2b8bff6f66fd90ac658d0ae0d7f9a83ffadfd77f [diff] |
[clang] Remove intrusive reference count from `DiagnosticOptions` (#139584)
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.
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