[PATCH] D14313: Add a libLTO diagnostic handler that supports lto_get_error_message API

[Rafael Espíndola via llvm-commits]

> I am actually not too satisfied with this patch myself, because I realize that the LTO client can call lto_codegen_set_diagnostic_handler() to set a new diagnostic handler, which however does not seem to change the handleLibLTODiagnostic() method installed by this patch here (the "IRLinker" member of the LTOCodeGenerator class does not provide a method to change its diagnostic handler).
>

Interesting.

Since we give access to the diagnostic handler, could we just
deprecate and eventually remove lto_get_error_message?

As for changing the diagnostic handler. It seems odd to support
changing it in the middle of the link. What I would suggest is
changing IRLinker to a std::unique_ptr that is constructed on first
use and documented that lto_codegen_set_diagnostic_handler cannot be
used once setModule or addModule has been called.

Cheers,
Rafael