lib/gc-pbkdf2-sha1.c: Remove comments from RFC 2898.

[gnulib.git] / m4 / lib-ignore.m4

diff --git a/m4/lib-ignore.m4 b/m4/lib-ignore.m4
index 319cf98..e518f81 100644 (file)
--- a/m4/lib-ignore.m4
+++ b/m4/lib-ignore.m4
@@ -12,31 +12,31 @@ AC_DEFUN([gl_IGNORE_UNUSED_LIBRARIES],
   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"