Re: lib-ignore: link error with Sun C++ compiler

[Ralf Wildenhues]

Hi Bruno,

* Bruno Haible wrote on Sat, Mar 20, 2010 at 11:52:25PM CET:
>       lib-ignore: Determine different options for different compilers.
>       * m4/lib-ignore.m4 (gl_IGNORE_UNUSED_LIBRARIES): Set a variable which
>       depends on the current language (C/C++/Fortran). Don't set LDFLAGS.
>       Add comments.
>       (_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS): New macro.
>       * NEWS: Mention the change.

This patch looks good to me, except that I didn't think of another
complication: when libtool is used to create a shared library, it
will honor and translate '-Wl,-z,ignore' to '-Qoption ld -z -Qoption ld
ignore' if needed, but it will drop a '-Qoption ld -z,ignore' on the
command line.  This only concerns library creation, not program
creation.  This is arguably a limitation in libtool; I'm not sure
whether it is the best idea to fix libtool, but that could be done.
WDYT?

The other very minor nit that I can think of is that the $wl issue is
more general than just only for lib-ignore.m4 -- it basically concerns
all linker flags that you ever need.  One generalization could be to
require libtool or config.rpath, and use information from that.

Autoconf does not document either of
  _AC_LANG_ABBREV
  _AC_LANG_PREFIX
  _AC_LANG
  _AC_LANG_DISPATCH

all of which are needed in order to write a patch like this.
We could add a section about low-level language flags in autoconf.texi
(when and if we're ready to commit to semantics).

Thank you,
Ralf