Re: AC_LIB_HAVE_LINKFLAGS is broken for cross building

[Bruno Haible]

Hi,

Jan Nieuwenhuizen wrote:
> AC_LIB_HAVE_LINKFLAGS is broken for cross building, it looks
> in $prefix/lib, which is usually /usr/lib/, which is usually
> right.
> 
> When cross building using a cross compiler for a different
> host root, say /home/janneke/vc/gub/target/mingw/root, things
> go horribly wrong.

The issue is not with cross building or not (test "$cross_compiling" = yes),
but with using a DESTDIR = /home/janneke/vc/gub/target/mingw/root.

See:

  - In native compiles without DESTDIR, looking up libraries in $prefix/lib
    is desired: The user expects the configuration to find programs that
    he has installed earlier with the same --prefix.

  - In cross-compiles without DESTDIR (oh yes, that exists: I have done
    cross-compiles with --prefix=/cross/sparc64-linux and similar),
    looking up libraries in $prefix/lib is desired as well.

  - In native compiles with DESTDIR - this mode is typically used by
    package distributors that want to make a clear distinction between
    the build machine and the end-user's machine, even if the $host is
    the same -, looking up libraries in $prefix/lib is undesired.

  - In cross-compiles with DESTDIR - your situation - it is undesired
    as well.

So, when there is a DESTDIR, looking up libraries in $prefix/lib is
undesired. There is a set of configure option for this:
--without-libxyz-prefix, one for each library libxyz.

For example, gettext's "configure --help" contains:

  --without-libpth-prefix     don't search for PACKLIBS in includedir and libdir
  --without-libiconv-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libintl-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libglib-2.0-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libcroco-0.6-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libunistring-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libxml2-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libncurses-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libtermcap-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libxcurses-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libcurses-prefix     don't search for PACKLIBS in includedir and 
libdir
  --without-libexpat-prefix     don't search for PACKLIBS in includedir and 
libdir

> suggestion to revert back to AC_CHECK_LIB

This would disable the search in $prefix/lib and $prefix/include for all users,
not only the compilations with DESTDIR. It would be seen as a regression by
the majority of the users.

Whereas for the users in your situation - a minority of the users -, the
desired behaviour is attainable through configure options.

Bruno
--
In memoriam Ilan Ramon <http://en.wikipedia.org/wiki/Ilan_Ramon>