Re: MinGW build on master fails with Error 127

[Eli Zaretskii <eliz@gnu.org>]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: emacs-devel@gnu.org
> Date: Sat, 24 Dec 2022 18:08:10 +0100
> 
> > And as long as I have your attention: what about the switch to UCRT64?
> > Does Emacs need something in its Makefile's to specify linking against
> > MSVCRT, even though UCRT64 is the default?  The information at
> >
> >   https://www.msys2.org/news/#2022-10-29-changing-the-default-environment-from-mingw64-to-ucrt64
> >
> > doesn't provide any details about that.
> 
> See
> 
> https://github.com/msys2/MINGW-packages/tree/master/mingw-w64-emacs

There's nothing there regarding the runtime against which Emacs is
being linked.  How does GCC/ld know which runtime to link against?  Up
until now GCC would call the linker with the -lmsvcrt switch, so does
it now use some other switch?  And what can users do to force MinGW64
to link against MSVCRT, if they so wish?

> There is a patch specific for UCRT support. It's quite simple although
> the workaround for close_stream doesn't inspire confidence, hints that
> there might be subtle differences on the behavior of C runtime
> functions.

It's a beginning of a very long journey, to learn about UCRT what
we've invested decades to learn about MSVCRT.  And the patch indeed is
not really acceptable, as it disables useful behavior without a
reasonable explanation.

Are the sources of UCRT available somewhere (as MSVCRT sources were)?