Re: gl_IGNORE_UNUSED_LIBRARIES sets --as-needed on HP-UX but should not

[Paul Eggert]

address@hidden (Bob Proulx) writes:

> While building coreutils on HP-UX 11.11 using the native hp c compiler
> I noticed that gnulib's gl_IGNORE_UNUSED_LIBRARIES causes --as-needed
> to be inadvertently used where it is not a valid option there.  It
> does not actually break the coreutils build and is why the warnings it
> produced went undetected.

Thanks for mentioning that.  I installed the following to fix this,
and to detect the problem Ralf noted.

2006-06-19  Paul Eggert  <address@hidden>

        * m4/lib-ignore.m4 (gl_IGNORE_UNUSED_LIBRARIES):
        Use -Wl,--as-needed, not bare --as-needed, since HP-UX 11.11
        cc merely issues a bunch of annoying warnings for --as-needed
        (this problem was reported by Bob Proulx).  Also, try linking with
        -lm to detect a bug in binutils 2.16 (this problem was reported
        by Ralf Wildenhues).

--- m4/lib-ignore.m4    19 Jun 2006 07:19:00 -0000      1.4
+++ m4/lib-ignore.m4    20 Jun 2006 05:57:05 -0000
@@ -13,12 +13,21 @@ AC_DEFUN([gl_IGNORE_UNUSED_LIBRARIES],
     [gl_cv_ignore_unused_libraries],
     [gl_cv_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="$LIBS -lm"
      # Use long option sequences like '-z ignore' to test for the feature,
      # to forestall problems with linkers that have -z, -i, -g, -n, etc. flags.
+     # GCC + binutils likes '-Wl,--as-needed'.
+     # GCC + Solaris ld likes '-Wl,-z,ignore'.
+     # Sun C likes '-z ignore'.
+     # Don't try bare '--as-needed'; nothing likes it and the HP-UX 11.11
+     # native cc issues annoying warnings and then ignores it,
+     # which would cause us to incorrectly conclude that it worked.
      for gl_flags in \
        '-Wl,--as-needed' \
        '-Wl,-z,ignore' \
-       '--as-needed' \
        '-z ignore'
      do
        LDFLAGS="$gl_flags $LDFLAGS"
@@ -26,7 +35,8 @@ AC_DEFUN([gl_IGNORE_UNUSED_LIBRARIES],
         [gl_cv_ignore_unused_libraries=$gl_flags])
        LDFLAGS=$gl_saved_ldflags
        test "$gl_cv_ignore_unused_libraries" != none && break
-     done])
+     done
+     LIBS=$gl_saved_libs])
 
   test "$gl_cv_ignore_unused_libraries" != none &&
     LDFLAGS="$LDFLAGS $gl_cv_ignore_unused_libraries"