Bug#731806: debian-installer: FTBFS on sparc: genisoimage errors

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Patrick Baggett:
> Could you explain the context around this code? Perhaps the source is
> not really "alignment safe" and could use some patching upstream? I'd
> be happy to provide advice or code samples.

The context was misposted to bug report 731806 as message #87:
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=731806#87
(but not with Cc to debian-sparc list).

Upstream is myself. :))
The code in question is by my unreachable libburn predecessors, though.

It belongs to the preparation of a thread start for one of five
occasions in libburn. SIGBUS happens at
  http://libburnia-project.org/browser/libburn/trunk/libburn/async.c#L149

The caller has a local struct (i.e. on stack) like (#L592, #L692):

   struct write_opts write;
   ...
   add_worker(Burnworker_type_writE, d,
                   (WorkerFunc) write_disc_worker_func, &o);

The called function gets its address as parameter "data" (#L135):

  static void add_worker(int w_type, struct burn_drive *d,
                         WorkerFunc f, void *data)

has a struct on heap (#L102, #L138, #L146):

   struct w_list{
       ...
       union w_list_data
       {
           ...
           struct write_opts write;
           ...
       } u;
   }
   ...
   struct w_list *a;
   ...
   a = calloc(1, sizeof(struct w_list));

The gesture which causes the SIGBUS is (#L149)

   a->u = *(union w_list_data *)data;

which is not what i personally would use, but should be fully legal
nevertheless.

The SIGBUS vanishes if i compile without gcc -O2, or if i replace
the "a->u =" gesture by

   memcpy(&(a->u), data, sizeof(union w_list_data));

which i deem equivalent (and more my personal style).


Have a nice day :)

Thomas