[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, 6 insertions, 6 deletions

diff --git a/clang/unittests/Frontend/OutputStreamTest.cpp b/clang/unittests/Frontend/OutputStreamTest.cpp
index 0eda3a1..dfb5a54 100644
--- a/clang/unittests/Frontend/OutputStreamTest.cpp
+++ b/clang/unittests/Frontend/OutputStreamTest.cpp
@@ -61,10 +61,10 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamShared) {
   raw_string_ostream VerboseStream(VerboseBuffer);
 
   Compiler.setOutputStream(std::make_unique<raw_null_ostream>());
-  IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
-  Compiler.createDiagnostics(
-      *llvm::vfs::getRealFileSystem(),
-      new TextDiagnosticPrinter(llvm::nulls(), &*DiagOpts), true);
+  DiagnosticOptions DiagOpts;
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem(),
+                             new TextDiagnosticPrinter(llvm::nulls(), DiagOpts),
+                             true);
   Compiler.setVerboseOutputStream(VerboseStream);
 
   bool Success = ExecuteCompilerInvocation(&Compiler);
@@ -91,10 +91,10 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamOwned) {
         std::make_unique<raw_string_ostream>(VerboseBuffer);
 
     Compiler.setOutputStream(std::make_unique<raw_null_ostream>());
-    IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
+    DiagnosticOptions DiagOpts;
     Compiler.createDiagnostics(
         *llvm::vfs::getRealFileSystem(),
-        new TextDiagnosticPrinter(llvm::nulls(), &*DiagOpts), true);
+        new TextDiagnosticPrinter(llvm::nulls(), DiagOpts), true);
     Compiler.setVerboseOutputStream(std::move(VerboseStream));
 
     Success = ExecuteCompilerInvocation(&Compiler);