Heads up: Recent status: emacs24/25 FTBFS since a long time on GNU/Hurd

[Svante Signell]

Hello bug-hurd ML,

Since a long time emacs FTBFS due to unknown reasons. The latest version
building was Debian 24.5+1-5, from 28 Nov 2015.

Even before successful builds were by pure luck. One suspicious issue is that
emacs use sbrk() for memory allocation, right? Notably sbrk() is not fool-proof
as implemented for Hurd in glibc: Is it or is it not?
Use of sbrk is found in files alloc.c, unexelf.c and gmalloc.c, which are
all compiled. Avoiding compilation of ralloc.c with 0001-Default-REL_ALLOC-to-
no.patch did not improve the situation.

First time I compiled emacs 25.1 from upstream it passed, second time not.
Compiling Debian versions always fails now (almost always a year ago, see
below). Mostly the build fails with temacs failing to execute: Killed or dumping
core depending on crsh server settings. In my oponion it's a real loss not to
gave a modern version of emacs25 available for use in GNU/Hurd (not everybody
use vi).

As written on IRC yesterday:
(23:17:22) srs: braunr: I'd like to add a few facts about emacs building on
GNU/Hurd: Latest successful build was 24.1+1-5 on 28 Nov 2015.
(23:17:22) srs: Installed then was: glibc-2.19-22, hurd-0.7-1, gnumach-1.6-1.
Trying to build that version now fails miserably,
(23:17:22) srs: (I just did that as well as on Nov 11 2016) so it is not only
not yet supported causing the build failure :(
(23:17:22) srs: The missing functions were not implemented  a year ago either.

And here is the latest gdb trace using the core file:
(unfortunately the rpctrace output is too large to include here)

emacs25-25.1+1/debian/build-x$ gdb ./src/bootstrap-emacs -c lisp/core
...
warning: core file may not match specified executable file.
[New process 24043]
[New process 1]

warning: Unexpected size of section `.reg2/24043' in core file.
Core was generated by `../src/bootstrap-emacs -batch --no-site-lisp --no-site-
file --eval (setq max-lis'.
Program terminated with signal SIGSEGV, Segmentation fault.

warning: Unexpected size of section `.reg2/24043' in core file.
#0  0x081a5c32 in backtrace_top () at eval.c:184
184     eval.c: No such file or directory.
[Current thread is 1 (process 24043)]
(gdb) info thre
  Id   Target Id         Frame 
* 1    process 24043     0x081a5c32 in backtrace_top () at eval.c:184
  2    process 1         warning: Unexpected size of section `.reg2/1' in core
file.
0x0520c9ac in ?? ()
(gdb) thread apply all bt full

Thread 2 (process 1):
#0  0x0520c9ac in ?? ()
No symbol table info available.

Thread 1 (process 24043):
#0  0x081a5c32 in backtrace_top () at eval.c:184
        pdl = 0x358d78
#1  near_C_stack_top () at eval.c:202
No locals.
#2  0x0814aaed in stack_overflow (siginfo=0x84d573c <sigsegv_stack+40924>)
    at sysdep.c:1659
        addr = 0x8d31cd8 <error: Cannot access memory at address 0x8d31cd8>
        bot = 0x98128c7 ""
        top = <optimized out>
#3  handle_sigsegv (sig=11, siginfo=0x84d573c <sigsegv_stack+40924>, 
    arg=0x84d5548 <sigsegv_stack+40424>) at sysdep.c:1691
        fatal = false
#4  0x0522da72 in ?? ()
No symbol table info available.
#5  0x0000000b in ?? ()
No symbol table info available.
#6  0x084d573c in sigsegv_stack ()
No symbol table info available.
#7  0x084d5548 in sigsegv_stack ()
No symbol table info available.
#8  0x05257600 in ?? ()
No symbol table info available.
#9  0x0522da76 in ?? ()
No symbol table info available.
#10 0x084d5460 in sigsegv_stack ()
No symbol table info available.
#11 0x00000001 in ?? ()
No symbol table info available.
#12 0x00000000 in ?? ()
No symbol table info available.
#0  0x0520c9ac in ?? ()
  Id   Target Id         Frame 
  1    process 24043     0x081a5c32 in backtrace_top () at eval.c:184
* 2    process 1         0x0520c9ac in ?? ()