The way we parse `DiagnosticOptions` is a bit involved.
`DiagnosticOptions` are parsed as part of the cc1-parsing function `CompilerInvocation::CreateFromArgs` which takes `DiagnosticsEngine` as an argument to be able to report errors in command-line arguments. But to create `DiagnosticsEngine`, `DiagnosticOptions` are needed. This is solved by exposing the `ParseDiagnosticArgs` to clients and making its `DiagnosticsEngine` argument optional, essentially breaking the dependency cycle.
The `ParseDiagnosticArgs` function takes `llvm::opt::ArgList &`, which each client needs to create from the command-line (typically represented as `std::vector<const char *>`). Creating this data structure in this context is somewhat particular. This code pattern is copy-pasted in some places across the upstream code base and also in downstream repos. To make things a bit more uniform, this patch extracts the code into a new reusable function: `CreateAndPopulateDiagOpts`.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D108918
555a817d1d