AC_CACHE_CHECK([for flag to ignore unused libraries],
[gl_cv_ignore_unused_libraries],
[gl_cv_ignore_unused_libraries=none
- AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [gl_ldd_output0=`(ldd conftest$ac_exeext) 2>/dev/null` ||
- gl_ldd_output0=])
- if test "$gl_ldd_output0"; then
- gl_saved_ldflags=$LDFLAGS
- gl_saved_libs=$LIBS
- LIBS="$LIBS -lm"
+ gl_saved_ldflags=$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 '-z ignore'.
+ # 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 \
+ '-Wl,--as-needed' \
+ '-Wl,-z,ignore' \
+ '-z ignore'
+ do
+ LDFLAGS="$gl_flags $LDFLAGS"
AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [gl_ldd_output1=`(ldd conftest$ac_exeext) 2>/dev/null` ||
- gl_ldd_output1=])
- if test "$gl_ldd_output1" && test "$gl_ldd_output0" != "$gl_ldd_output1"
- then
- for gl_flags in '-Xlinker -zignore' '-zignore'; do
- LDFLAGS="$gl_flags $LDFLAGS"
- AC_LINK_IFELSE([AC_LANG_PROGRAM()],
- [if gl_ldd_output2=`(ldd conftest$ac_exeext) 2>/dev/null` &&
- test "$gl_ldd_output0" = "$gl_ldd_output2"; then
- gl_cv_ignore_unused_libraries=$gl_flags
- fi])
- LDFLAGS=$gl_saved_ldflags
- test "gl_cv_ignore_unused_libraries" != none && break
- done
- fi
- LIBS=$gl_saved_LIBS
- fi])
+ [gl_cv_ignore_unused_libraries=$gl_flags])
+ LDFLAGS=$gl_saved_ldflags
+ test "$gl_cv_ignore_unused_libraries" != none && break
+ done
+ LIBS=$gl_saved_libs])
test "$gl_cv_ignore_unused_libraries" != none &&
LDFLAGS="$LDFLAGS $gl_cv_ignore_unused_libraries"