Re: building i386 world on amd64 host: failed _at_svn

On Jul 28, 2013, at 15:15, Dmitry Morozovsky <marck_at_rinet.ru> wrote:
...
> on my builder I have consistent error:
> 
> /usr/obj/i386.i386/FreeBSD/pristine/src.current/usr.bin/svn/svn/../lib/libsvn_subr/libsvn_subr.a(named_atomic.o): 
> In function `svn_named_atomic__cmpxchg':
> named_atomic.c:(.text+0xed): undefined reference to 
> `__sync_val_compare_and_swap_8'
> /usr/obj/i386.i386/FreeBSD/pristine/src.current/usr.bin/svn/svn/../lib/libsvn_subr/libsvn_subr.a(named_atomic.o): 
> In function `svn_named_atomic__add':
> named_atomic.c:(.text+0x193): undefined reference to `__sync_add_and_fetch_8'
> /usr/obj/i386.i386/FreeBSD/pristine/src.current/usr.bin/svn/svn/../lib/libsvn_subr/libsvn_subr.a(named_atomic.o): 
> In function `svn_named_atomic__write':
> named_atomic.c:(.text+0x1f3): undefined reference to 
> `__sync_lock_test_and_set_8'

After a bit of private conversation with Dmitry, it turned out he was
building using WITHOUT_CLANG, e.g. gcc is used for everything.  Now,
this is *not* a problem specific to cross-building: head will not build
on i386 with gcc at all!  It results in exactly the same error shown
above.

This is because Subversion has a few wrapper routines for atomic
operations, and these are implemented in terms of the __sync_xxx
compiler builtins, since usr.bin/svn/svn_private_config.h has
SVN_HAS_ATOMIC_BUILTINS defined.  On i386, gcc apparently cannot inline
the 64 bit versions of these builtins, so it inserts a call to an
external function instead, leading to a link error.

Eventually, we could put such functions in libc, but for now it might be
better to turn off the SVN_HAS_ATOMIC_BUILTINS define in case of !clang
&& i386, e.g.:

Index: usr.bin/svn/svn_private_config.h
===================================================================
--- usr.bin/svn/svn_private_config.h    (revision 254300)
+++ usr.bin/svn/svn_private_config.h    (working copy)
_at__at_ -153,7 +153,9 _at__at_
 #define SVN_FS_WANT_DB_PATCH 14

 /* Define if compiler provides atomic builtins */
+#if defined(__i386__) && !defined(__clang__)
 #define SVN_HAS_ATOMIC_BUILTINS 1
+#endif

 /* Is GNOME Keyring support enabled? */
 /* #undef SVN_HAVE_GNOME_KEYRING */

Alternatively, we could attempt to figure out why gcc doesn't want to
inline those 64 bit builtins on FreeBSD.  It seems to have no problem
doing so on the first Linux box I tried...

-Dimitry