Question about new warning system

[DJ Delorie]

> Is that behaviour documented somewhere I missed?

Sadly, no.  Actually, none of the diagnostic calls are documented.
The prototypes are even in toplev.h instead of diagnostic.h, between
"fatal_insn_not_found() and "rest_of_decl_compilation()".  It's quite
haphazard.

The diagnostic_info structure does have this comment:

  /* Which OPT_* directly controls this diagnostic.  */
  int option_index;

The word "controls" implies, well, control.  But I don't think that
counts as the kind of documentation you're thinking about.