Allow -x c++ to work

[vchuravy]

No description provided.

[vchuravy]

Attempt at fixing #430 (comment)

[vchuravy]

Struggles still with:

/// Severity of a diagnostic.
enum MlirDiagnosticSeverity {
  MlirDiagnosticError,
  MlirDiagnosticWarning,
  MlirDiagnosticNote,
  MlirDiagnosticRemark
};
typedef enum MlirDiagnosticSeverity MlirDiagnosticSeverity;

[vchuravy]

Motivating PR in MLIR.jl JuliaLLVM/MLIR.jl#10, but of course kinda ugly since we suddenly have to deal with new things...

[Gnimuc]

Allowing -x c++ is not enough for generic C++ support, we need to add C++ standard library and system headers like what has been done in ClangCompiler.jl: https://github.com/Gnimuc/ClangCompiler.jl/blob/master/src/platform/system.jl

[Gnimuc]

Struggles still with:

/// Severity of a diagnostic.
enum MlirDiagnosticSeverity {
  MlirDiagnosticError,
  MlirDiagnosticWarning,
  MlirDiagnosticNote,
  MlirDiagnosticRemark
};
typedef enum MlirDiagnosticSeverity MlirDiagnosticSeverity;

Is this problem caused by the audit step?

I added an option no_audit in this PR which might be helpful...

[vchuravy]

is not enough for generic C++ support, we need to add C++ standard library and system headers like what has been done in ClangCompiler.jl

Yeah I don't need generic C++ support, more C headers written by C++ people... E.g. MLIR headers contain some C++-ism

[vchuravy]

Is this problem caused by the audit step?

No the issue is that C++ mode changes the representation of some of the Clang nodes.
I needed #435 to sucesfully parse the MLIR headers.