[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 #23 from Iain Sandoe <iains at gcc dot gnu.org> 2011-02-01 17:28:36 UTC ---
(In reply to comment #22)
> My only comment is that the likely users of FSF gcc are also likely builders of
> ported unix code. So gcc 4.6 needs a big fat warning that existing ported unix
> code will have to be vetted for the use of flat-namespace and the linkages
> manually adjusted. Otherwise will users of gcc 4.6 will unknowingly miscompile
> lots of existing unix code. Since we don't link this way in gcc 4.5, I don't
> see why we can't just revert the behavior and postpone this change until gcc
> 4.7 when it can be more carefully done.

I am concerned that we push the balloon in one place and it pops out in
another.
We have made a lot of effort to avoid libSystem linkage before the ext to avoid
other reported issues with unwinding and Java IIRC.  I am not too keen simply
to go round in circles (we need proper fixes, of course).

This might be a reasonable compromise until the proper fixes are forthcoming:


Index: gcc/config/darwin.h
===================================================================
--- gcc/config/darwin.h    (revision 169490)
+++ gcc/config/darwin.h    (working copy)
@@ -327,12 +331,16 @@ extern GTY(()) int darwin_ms_struct;
    "%{static-libgcc|static: -lgcc_eh -lgcc;                   \
       shared-libgcc|fexceptions|fgnu-runtime:                   \
        %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_s.10.4)       \
-       %:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5)   \
+       %{flat_namespace:                           \
+         %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5)       \
+        :%:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5)}\
        %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_ext.10.4)       \
        %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_ext.10.5)       \
        -lgcc ;                                   \
       :%:version-compare(>< 10.3.9 10.5 mmacosx-version-min= -lgcc_s.10.4) \
-       %:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5)   \
+       %{flat_namespace:                           \
+         %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5)       \
+        :%:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5)}\
        %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_ext.10.4)       \
        %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_ext.10.5)       \
        -lgcc }"