X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Flib-ignore.m4;h=0236cb545265cd880e2d577f33d394c9d4d893a4;hb=fc80165c92e8b92da6e88e4fdb9c472125124fa0;hp=319cf987a2b3ff4307501390ceb3a912ed57e201;hpb=14bf04a59fbfa9ae7a9b55f7885ed96a5f0341ac;p=gnulib.git

diff --git a/m4/lib-ignore.m4 b/m4/lib-ignore.m4
index 319cf987a..0236cb545 100644
--- a/m4/lib-ignore.m4
+++ b/m4/lib-ignore.m4
@@ -1,6 +1,6 @@
 # If possible, ignore libraries that are not depended on.
 
-dnl Copyright (C) 2006 Free Software Foundation, Inc.
+dnl Copyright (C) 2006, 2009-2010 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.
@@ -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"