On Tue, 4 Oct 2022 at 19:05, Jonathan Wakely wrote:
>
> On Tue, 4 Oct 2022 at 17:51, Jonathan Wakely via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
> >
> > Does anybody see any issues with generating the list of error numbers at
> > build time?
> >
> >
> > -- >8 --
> >
> > Instead of having several very similar target-specific headers with
> > slightly different sets of enumerators, generate the error_constants.h
> > file as part of the build. This ensures that all enumerators are always
> > defined, with the value from the corresponding errno macro if present,
> > or a libstdc++-specific alternative value.
> >
> > The libstdc++-specific values will be values greater than the positive
> > integer _GLIBCXX_ERRC_ORIGIN, which defaults to 9999 but can be set in
> > os_defines.h if a more suitable value exists for the OS (e.g. ELAST
> > could be used for BSD targets).
> ...
> > +${CXXCPP} -P -D_POSIX_C_SOURCE=200809L -x c++ "$constants_h" \
> > +  | sed -e '1,/^GLIBCXX ERROR CONSTANTS BELOW HERE$/d' \
> > +  >> "$output_h" || exit $?
>
> Gah, this is the wrong version of the script! It's supposed to replace
> unexpanded EXXX tokens with __LINE__ (which is why #line is used to
> set the origin) but I seem to have committed the wrong version.
>
> Let me dig that out of my git reflog ...

I was looking on the wrong machine. Here's the working patch that
expands undefined EXXX constants to __LINE__, which has been offset by
the _GLIBCXX_ERRC_ORIGIN value.