Re: Errors cross-compiling gdbserver with glibc-2.34

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 08/09/2021 21:10, Chris Packham via Libc-help wrote:
> 
> On 9/08/21 9:46 pm, Florian Weimer wrote:
> > * Chris Packham via Libc-help:
> >
> >> I'm looking at updating crosstool-ng to add glibc-2.34. I can generate a
> >> toolchain fine but when I try to build gdbserver (which can be enabled
> >> as part of the crosstool-ng build) I get some odd gnulib build errors.
> >>
> >> https://github.com/crosstool-ng/crosstool-ng/pull/1570#issuecomment-893784531
> >>
> >> I can disable building gdbserver as part of crosstool-ng and
> >> successfully generate a toolchain. But when I use that toolchain to
> >> manually build gdbserver I get the same error (included below as it has
> >> a bit more useful output than on the link above).
> >>
> >>     CXX    amd64-linux-siginfo.o
> >> In file included from
> >> /home/ctng/x-tools/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/sysroot/usr/include/bits/sigstksz.h:24,
> >>                    from
> >> /home/ctng/x-tools/x86_64-unknown-linux-gnu/x86_64-unknown-linux-gnu/sysroot/usr/include/signal.h:328,
> >>                    from build-gnulib-gdbserver/import/signal.h:52,
> >>                    from
> >> ../../../gdb-9.2/gdb/gdbserver/../nat/amd64-linux-siginfo.c:20:
> >> build-gnulib-gdbserver/import/unistd.h:135:3: error: #error "Please
> >> include config.h first."
> > gnulib apparently overrides <unistd.h> with an incompatible header.
> > There is nothing that glibc can do about this.
> 
> Yes I came to the same conclusion after I send my initial email.

what makes gnulib want to override unistd.h?
(usually there is some portability check that fails)

i think you should look at that. (it may affect more
than just old gdb builds)

> 
> As of glibc commit 6c57d32048 ("sysconf: Add 
> _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305]") there is a new include chain 
> from signal.h to unistd.h. There's nothing wrong with that it just 
> happens that unistd.h is one of the headers that the gnulib bundled with 
> gdb overrides.
> 
> It's likely that I'll end up needing to patch gdb to fix this (currently 
> no idea what the patch would look like). I haven't attempted to compile 
> a newer gdb so I don't know if this is something already dealt with 
> (there is a source code re-arrangement in gdb-10 that requires some 
> changes in crosstool-ng that I haven't got round to). If anyone that 
> works with gnulib and/or gdb is on this list I'd like to know if you've 
> already encountered this.
> 
> Hopefully this is at least a breadcrumb for future web searchers to follow.
> 
> > Thanks,
> > Florian