Re: libsigsegv questions

[Bruno Haible]

[switching to bug-gnulib]

Eric Blake wrote in
<http://lists.gnu.org/archive/html/bug-gnu-utils/2008-06/msg00006.html>:
> When I get around to dumping m4's own stackovf.c and
> replacing it with libsigsegv when available, and gnulib's c-stack when the
> external library is not present, I will stick with the external dependency
> (and not distribute libsigsegv as a subproject).

When you are doing that, it would be useful to move the "c-stack or libsigsegv"
alternative code into gnulib. Reason: c-stack nowadays only supports one-third
of the available platforms:
  Linux, HP-UX, OSF/1, Solaris
whereas libsigsegv also supports the platforms
  MacOS X, FreeBSD, OpenBSD, NetBSD, AIX, IRIX, Cygwin, mingw, BeOS.
I think every package which uses c-stack would profit from being able to
use libsigsegv if it's already installed.

This would mean
  1) Putting the sigsegv.m4 macro from GNU clisp into gnulib, incorporating
     it into the c-stack module.
  2) Ensure that when c-stack compiles but does not work (yes, there are such
     systems, e.g. badly maintained arm-linux ports or similar, and broken
     sigaltstack implementations), libsigsegv is used when available.
  3) Finding a common API, bridging over c-stack and libsigsegv.

> | For your information, attached you find the libsigsegv detection macro from
> | GNU clisp.
> 
> That used AC_LIB_PREPARE_PREFIX, AC_LIB_RPATH, AC_LIB_LINKFLAGS_BODY, and
> AC_LIB_APPENDTOVAR, all in the autoconf namespace, but none of them
> provided by autoconf (yet).  Where are they defined, and are they worth
> pushing into autoconf proper (for 2.63 or later) as useful macros?

These macros are defined in the gnulib 'havelib' module. Yes the autoconf
maintainers already asked me to propose a patch for inclusion in autoconf,
3 years ago, but I didn't get around to making it perfect so far. I would love
it if I could send in a less perfect patch and have someone help me to
"make it fit for autoconf".

Bruno