[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.

1 files changed, 4 insertions, 4 deletions

diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index 4b407a0..84feff8 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -95,9 +95,9 @@ CreateCI(const llvm::opt::ArgStringList &Argv) {
 
   // Buffer diagnostics from argument parsing so that we can output them using
   // a well formed diagnostic object.
-  IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
+  DiagnosticOptions DiagOpts;
   TextDiagnosticBuffer *DiagsBuffer = new TextDiagnosticBuffer;
-  DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagsBuffer);
+  DiagnosticsEngine Diags(DiagID, DiagOpts, DiagsBuffer);
   bool Success = CompilerInvocation::CreateFromArgs(
       Clang->getInvocation(), llvm::ArrayRef(Argv.begin(), Argv.size()), Diags);
 
@@ -173,10 +173,10 @@ IncrementalCompilerBuilder::create(std::string TT,
   // Buffer diagnostics from argument parsing so that we can output them using a
   // well formed diagnostic object.
   IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
-  IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts =
+  std::unique_ptr<DiagnosticOptions> DiagOpts =
       CreateAndPopulateDiagOpts(ClangArgv);
   TextDiagnosticBuffer *DiagsBuffer = new TextDiagnosticBuffer;
-  DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagsBuffer);
+  DiagnosticsEngine Diags(DiagID, *DiagOpts, DiagsBuffer);
 
   driver::Driver Driver(/*MainBinaryName=*/ClangArgv[0], TT, Diags);
   Driver.setCheckInputsExist(false); // the input comes from mem buffers