[Bug target/47558] 163267 breaks exception traceback in xplor-nih

["iains at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47558

--- Comment #58 from Iain Sandoe <iains at gcc dot gnu.org> 2011-02-05 12:21:51 UTC ---
The response from Nick indicates that the documentation for -flat_namespace and
two-level namespaces is correct and up to date - so we should proceed with a
fix.

>From a general specs point of view, I don't think we should be including
libSystem in REAL_LIBGCC_SPEC, it kinda defeats the object of separating %G and
%L.  If we don't care about this, then let's just set one of those to "" to
avoid future confusion. 

* We also need to watch out for the fact that fortran and java both hijack *lib
to interpose their library lists.

Here is a patch that should achieve the same thing as
http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00274.html, but using the
LINK_GCC_C_SEQUENCE_SPEC (essentially a slightly more sophisticated version of
comment #17).

It is probably harmless to insert libSystem before libgcc_s on Darwin 9 - since
there are no unwinder symbols in Darwin 9's libSystem -- however, for the sake
of consistency with other tools, I've wrapped it specifically for Darwin >= 10.

(sometime I'd also like to split -no_compact_unwinder into its own macro - and
provide a user way to switch it off - although it's still needed by default, as
things stand).

In addition to the cases already posted; for fortran, I get a link order of:
 -lgfortran -lSystem -lgcc_ext.10.5 -lgcc -lquadmath -lm -lgcc_ext.10.5 -lgcc
-lSystem

(incidentally, the presence of the unfiltered -lm in that spec means an
effective additional -lSystem)

and with -mmacosx-version-min=10.5:
 -lgfortran -lgcc_s.10.5 -lgcc_ext.10.5 -lgcc -lquadmath -lm -lgcc_s.10.5
-lgcc_ext.10.5 -lgcc -lSystem 

for java 

-lSystem -lgcc_ext.10.5 -lgcc -lgcj /usr/lib/libiconv.dylib -lz
-allow_stack_execute -lgcc_ext.10.5 -lgcc -lSystem 

and with -mmacosx-version-min=10.5:
-lgcc_s.10.5 -lgcc_ext.10.5 -lgcc -lgcj /usr/lib/libiconv.dylib -lz
-allow_stack_execute -lgcc_s.10.5 -lgcc_ext.10.5 -lgcc -lSystem

====

- I can't test the xplor package tho' so Jack might wish to do so.

*** Note that, during looking at this, I discovered that libjava/libltdl has an
acinclude.m4 that uses several obsolete macros, including one that inserts
-flat_namespace in the sequence for undefined symbol handling - on at least
Darwin 9 and 10.  Needs addressing as a separate problem, of course.   A
temporary workaround for that is to set MACOSX_DEPLOYMENT_TARGET before
building java. ***

====

IMO, we still need to fix things such that (a) we don't need to link against
libgcc.a when doing shared linking (b) we change the name of our export lib
(e.g. to libgcc_ext.1.dylib) and only export the symbols we need. 


Index: gcc/config/darwin10.h
===================================================================
--- gcc/config/darwin10.h    (revision 169811)
+++ gcc/config/darwin10.h    (working copy)
@@ -1,5 +1,5 @@
 /* Target definitions for Darwin (Mac OS X) systems.
-   Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+   Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
    Contributed by Jack Howarth <howarth@bromo.med.uc.edu>.

 This file is part of GCC.
@@ -18,8 +18,16 @@ You should have received a copy of the GNU General
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */

+#undef LIB_SPEC
+#define LIB_SPEC "%{!static: -lSystem }"
+
 /* Fix PR41260 by passing -no_compact_unwind on darwin10 and later until
-unwinder in libSystem is fixed to digest new epilog unwinding notes. */
+   unwinder in libSystem is fixed to digest new epilog unwinding notes. */

-#undef LIB_SPEC
-#define LIB_SPEC "%{!static:-no_compact_unwind -lSystem}"
+/* FIXME: Work around PR47558 by linking against libSystem ahead of 
+   libgcc_ext. */
+#undef  LINK_GCC_C_SEQUENCE_SPEC
+#define LINK_GCC_C_SEQUENCE_SPEC \
+"%:version-compare(>= 10.6 mmacosx-version-min= -no_compact_unwind) \
+   %{!static:%{!static-libgcc: \
+      %:version-compare(>= 10.6 mmacosx-version-min= -lSystem) } } %G %L"