bug#52711: undefined reference to '__muloti4'

[Alan Third]

On Tue, Dec 21, 2021 at 10:17:22PM +0200, Eli Zaretskii wrote:
> > Date: Tue, 21 Dec 2021 20:12:07 +0000
> > From: Alan Third <alan@idiocy.org>
> > Cc: bug-gnu-emacs@gnu.org, Paul Eggert <eggert@cs.ucla.edu>
> > 
> > On Tue, Dec 21, 2021 at 09:47:49PM +0200, Eli Zaretskii wrote:
> > > > Date: Tue, 21 Dec 2021 19:30:42 +0000
> > > > From: Alan Third <alan@idiocy.org>
> > > > 
> > > > I no longer seem to be able to build the master branch. I'm getting
> > > > this error:
> > > > 
> > > >   CCLD     temacs
> > > > fileio.c:6261: error: undefined reference to '__muloti4'
> > > > clang: error: linker command failed with exit code 1 (use -v to see 
> > > > invocation)
> > > > make[2]: *** [Makefile:697: temacs] Error 1
> > > > 
> > > > I had a look but couldn't see where the problem comes from. I'm using
> > > > clang on Debian testing, if that matters.
> > > 
> > > Try using "nm -A fileio.o" to see what is that function and which code
> > > calls it.
> > > 
> > > If nothing else helps, try bisecting.  (But my crystal ball says it
> > > isn't Emacs that changed, it's something else on that system.)
> > 
> > Looks like it's gnulib:
> > 
> > f05a93e8232e6f56458ac16d733b03e96a63e930 is the first bad commit
> > commit f05a93e8232e6f56458ac16d733b03e96a63e930
> > Author: Paul Eggert <eggert@cs.ucla.edu>
> > Date:   Sat Dec 18 16:12:38 2021 -0800
> >     Update from gnulib
> > 
> > I think the actual call is deep within some nested macros.
> 
> If you do "nm -A libgnu.a", do you see this function in the library?
> If so, from what file does it come?

No, it's not listed in the output...

OK, so some searching shows it's a clang bug that was only just fixed
last month, so won't be in whatever version of clang I've got access
to.

https://bugs.llvm.org/show_bug.cgi?id=16404

As described in that thread, adding this to LDFLAGS sorts it:

    --rtlib=compiler-rt --unwindlib=libgcc
-- 
Alan Third