# If possible, ignore libraries that are not depended on.

dnl Copyright (C) 2006, 2009-2014 Free Software Foundation, Inc.

dnl This file is free software; the Free Software Foundation

dnl gives unlimited permission to copy and/or distribute it,

dnl with or without modifications, as long as this notice is preserved.

dnl Written by Paul Eggert.

# gl_IGNORE_UNUSED_LIBRARIES

# --------------------------

# Determines the option to be passed to the C/C++/Fortran compiler, so that it

# omits unused libraries.

# Example (on Solaris):

# $ cc foo.c -lnsl; ldd ./a.out

#         libnsl.so.1 =>   /lib/libnsl.so.1

#         libc.so.1 =>     /lib/libc.so.1

#         libmp.so.2 =>    /lib/libmp.so.2

#         libmd.so.1 =>    /lib/libmd.so.1

#         libscf.so.1 =>   /lib/libscf.so.1

#         libdoor.so.1 =>  /lib/libdoor.so.1

#         libuutil.so.1 =>         /lib/libuutil.so.1

#         libgen.so.1 =>   /lib/libgen.so.1

#         libm.so.2 =>     /lib/libm.so.2

# $ cc foo.c -lnsl -Wl,-z,ignore; ldd ./a.out

#         libc.so.1 =>     /lib/libc.so.1

#         libm.so.2 =>     /lib/libm.so.2

#

# Note that the option works only for the C compiler, not for the C++

# compiler:

# - Sun C likes '-Wl,-z,ignore'.

#   '-Qoption ld -z,ignore' is not accepted.

#   '-z ignore' is accepted but has no effect.

# - Sun C++ and Sun Fortran like '-Qoption ld -z,ignore'.

#   '-Wl,-z,ignore' is not accepted.

#   '-z ignore' is accepted but has no effect.

#

# Sets and substitutes a variable that depends on the current language:

# - IGNORE_UNUSED_LIBRARIES_CFLAGS    for C

# - IGNORE_UNUSED_LIBRARIES_CXXFLAGS  for C++

# - IGNORE_UNUSED_LIBRARIES_FFLAGS    for Fortran

#

# Note that the option works only for direct invocation of the compiler, not

# through libtool: 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.

#

AC_DEFUN([gl_IGNORE_UNUSED_LIBRARIES],

[

  AC_CACHE_CHECK([for []_AC_LANG[] compiler flag to ignore unused libraries],

    [gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries],

    [gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries=none

     gl_saved_ldflags=$LDFLAGS

     gl_saved_libs=$LIBS

     # Link with -lm to detect binutils 2.16 bug with --as-needed; see

     # <http://lists.gnu.org/archive/html/bug-gnulib/2006-06/msg00131.html>.

     LIBS="$LIBS -lm"

     # Use long option sequences like '-z ignore' to test for the feature,

     # to forestall problems with linkers that have -z, -i, -g, -n, etc. flags.

     # GCC + binutils likes '-Wl,--as-needed'.

     # GCC + Solaris ld likes '-Wl,-z,ignore'.

     # Sun C likes '-Wl,-z,ignore'. '-z ignore' is accepted but has no effect.

     # Don't try bare '--as-needed'; nothing likes it and the HP-UX 11.11

     # native cc issues annoying warnings and then ignores it,

     # which would cause us to incorrectly conclude that it worked.

     for gl_flags in _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS

     do

       LDFLAGS="$gl_flags $LDFLAGS"

       AC_LINK_IFELSE([AC_LANG_PROGRAM()],

         [gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries=$gl_flags])

       LDFLAGS=$gl_saved_ldflags

       test "$gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries" != none &&

         break

     done

     LIBS=$gl_saved_libs

    ])

  IGNORE_UNUSED_LIBRARIES_[]_AC_LANG_PREFIX[]FLAGS=

  if test "$gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries" != none; then

    IGNORE_UNUSED_LIBRARIES_[]_AC_LANG_PREFIX[]FLAGS="$gl_cv_prog_[]_AC_LANG_ABBREV[]_ignore_unused_libraries"

  fi

  AC_SUBST([IGNORE_UNUSED_LIBRARIES_]_AC_LANG_PREFIX[FLAGS])

])

# _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS

# -----------------------------------

# Expands to the language dependent options to be tried.

AC_DEFUN([_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS],

[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])

# _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(C)

# --------------------------------------

m4_define([_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(C)],

[ '-Wl,--as-needed' \

  '-Wl,-z,ignore' \

  '-z ignore'

])

# _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(C++)

# ----------------------------------------

m4_define([_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(C++)],

[ '-Wl,--as-needed' \

  '-Qoption ld -z,ignore' \

  '-Wl,-z,ignore' \

  '-z ignore'

])

# _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(Fortran 77)

# -----------------------------------------------

m4_copy([_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(C++)],

        [_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(Fortran 77)])

# _gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(Fortran)

# --------------------------------------------

m4_copy([_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(Fortran 77)],

        [_gl_IGNORE_UNUSED_LIBRARIES_OPTIONS(Fortran)])