Don't discard -lgcc from `-lgcc -c -lgcc'

[Alexandre Oliva]

I've finally figured out why our duplicate-elimination is not as
outrageous as I had thought at first.  Marking libraries as
specialdeplibs is indeed a neat heuristics; see the comments in the
patch below.  Unfortunately, it doesn't catch the common case of the
libraries implicitly linked in by GCC, which affects our ability to
create correct C++ shared libraries with g++.  Fixed as follows.  Ok
to install?

Index: ChangeLog
from  Alexandre Oliva  <address@hidden>

        * ltmain.in: Mark duplicate libraries appearing in predeps and
        postdeps as specialdeplibs.  Explain the whole plan.

Index: ltmain.in
===================================================================
RCS file: /cvsroot/libtool/libtool/ltmain.in,v
retrieving revision 1.200.2.60
diff -u -p -r1.200.2.60 ltmain.in
--- ltmain.in 2001/04/08 10:03:52 1.200.2.60
+++ ltmain.in 2001/04/09 18:22:33
@@ -1630,6 +1630,18 @@ EOF
 
     if test $linkmode = lib; then
       libs="$predeps $libs $compiler_lib_search_path $postdeps"
+
+      # Compute libraries that are listed more than once in $predeps
+      # $postdeps and mark them as special (i.e., whose duplicates are
+      # not to be eliminated).
+      pre_post_deps=
+      for pre_post_dep in $predeps $postdeps; do
+        case "$pre_post_deps " in
+       *" $pre_post_dep "*) specialdeplibs="$specialdeplibs $pre_post_deps" ;;
+       esac
+       pre_post_deps="$pre_post_deps $pre_post_dep"
+      done
+      pre_post_deps=
     fi
 
     deplibs=
@@ -2373,6 +2385,20 @@ EOF
            case $deplib in
             -L*) new_libs="$deplib $new_libs" ;;
             *)
+             # And here is the reason: when a library appears more
+             # than once as an explicit dependence of a library, or
+             # is implicitly linked in more than once by the
+             # compiler, it is considered special, and multiple
+             # occurrences thereof are not removed.  Compare this
+             # with having the same library being listed as a
+             # dependency of multiple other libraries: in this case,
+             # we know (pedantically, we assume) the library does not
+             # need to be listed more than once, so we keep only the
+             # last copy.  This is not always right, but it is rare
+             # enough that we require users that really mean to play
+             # such unportable linking tricks to link the library
+             # using -Wl,-lname, so that libtool does not consider it
+             # for duplicate removal.
               case " $specialdeplibs " in
               *" $deplib "*) new_libs="$deplib $new_libs" ;;
               *)

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  address@hidden, redhat.com}
CS PhD student at IC-Unicamp        address@hidden, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me