[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, 5 insertions, 4 deletions

diff --git a/clang/unittests/Frontend/UtilsTest.cpp b/clang/unittests/Frontend/UtilsTest.cpp
index 47ca321..cf385a5 100644
--- a/clang/unittests/Frontend/UtilsTest.cpp
+++ b/clang/unittests/Frontend/UtilsTest.cpp
@@ -26,11 +26,12 @@ TEST(BuildCompilerInvocationTest, RecoverMultipleJobs) {
   std::vector<const char *> Args = {"clang", "--target=macho", "-arch",  "i386",
                                     "-arch", "x86_64",         "foo.cpp"};
   clang::IgnoringDiagConsumer D;
+  clang::DiagnosticOptions DiagOpts;
   CreateInvocationOptions Opts;
   Opts.RecoverOnError = true;
   Opts.VFS = new llvm::vfs::InMemoryFileSystem();
-  Opts.Diags = clang::CompilerInstance::createDiagnostics(
-      *Opts.VFS, new DiagnosticOptions, &D, false);
+  Opts.Diags = clang::CompilerInstance::createDiagnostics(*Opts.VFS, DiagOpts,
+                                                          &D, false);
   std::unique_ptr<CompilerInvocation> CI = createInvocation(Args, Opts);
   ASSERT_TRUE(CI);
   EXPECT_THAT(CI->getTargetOpts().Triple, testing::StartsWith("i386-"));
@@ -45,9 +46,9 @@ TEST(BuildCompilerInvocationTest, ProbePrecompiled) {
   FS->addFile("foo.h.pch", 0, llvm::MemoryBuffer::getMemBuffer(""));
 
   clang::IgnoringDiagConsumer D;
+  clang::DiagnosticOptions DiagOpts;
   llvm::IntrusiveRefCntPtr<DiagnosticsEngine> CommandLineDiagsEngine =
-      clang::CompilerInstance::createDiagnostics(*FS, new DiagnosticOptions, &D,
-                                                 false);
+      clang::CompilerInstance::createDiagnostics(*FS, DiagOpts, &D, false);
   // Default: ProbePrecompiled=false
   CreateInvocationOptions CIOpts;
   CIOpts.Diags = CommandLineDiagsEngine;