Re: PR13901

[Jack Howarth <howarth@bromo.med.uc.edu>]

On Mon, Apr 02, 2012 at 01:57:31PM +0200, Tristan Gingold wrote:
> 
> On Apr 2, 2012, at 12:44 PM, Tristan Gingold wrote:
> 
> > 
> > On Mar 30, 2012, at 3:42 PM, Jack Howarth wrote:
> > 
> >> Tristan,
> >>  Have you noticed that recent FSF gdb releases including 7.4 have been
> >> non-functional when built targeting i386-apple-darwin? The run-time failures
> >> have changed between 7.2 and 7.4. Currently the failure is exhibited as
> >> errors of the form...
> >> 
> >> (gdb) break main
> >> Breakpoint 1 at 0xd80: file himenoBMTxpa.c, line 71.
> >> (gdb) r
> >> Starting program: /Users/howarth/a.out 
> >> darwin_set_sstep: unknown flavour: 4
> >> Error calling thread_get_state for GP registers for thread 0x8451lxwarning:
> >> Mach error at "i386-darwin-nat.c:118" in function
> >> "i386_darwin_fetch_inferior_registers": (os/kern) invalid argument (0x4)
> >> 
> >> http://sourceware.org/bugzilla/show_bug.cgi?id=13901
> >> 
> >> Is this something that is trivial to fix? It would be nice if both MacPorts
> >> and fink could have a functional i386 build of FSF gdb. In fink, we currently
> >> have gdb restricted to x86_64 fink (although the x86_64-apple-darwin build
> >> can debug i386 binaries fine). MacPorts has left their gdb pacakge at 7.1
> >> (which I guess is that last version that worked for both i386-apple-darwin
> >> and x86_64-apple-darwin. Thanks in advance for any clarifications.
> > 
> > I now understand the issue:
> > 
> > gdb spawns bash to run the program, but the bash spawned is 64 bits, which is not understood by gdb...
> 
> Fixed by this patch (committed on trunk):
> 
> 2012-04-02  Tristan Gingold  <gingold@adacore.com>
> 
> 	PR gdb/13901
> 	* darwin-nat.c (darwin_execvp): Sey binary preference.
> 
> Index: darwin-nat.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/darwin-nat.c,v
> retrieving revision 1.31
> diff -c -r1.31 darwin-nat.c
> *** darwin-nat.c	14 Mar 2012 01:46:59 -0000	1.31
> --- darwin-nat.c	2 Apr 2012 11:55:36 -0000
> ***************
> *** 39,44 ****
> --- 39,45 ----
>   #include "value.h"
>   #include "arch-utils.h"
>   #include "bfd.h"
> + #include "bfd/mach-o.h"
>   
>   #include <sys/ptrace.h>
>   #include <sys/signal.h>
> ***************
> *** 1538,1543 ****
> --- 1539,1560 ----
>         return;
>       }
>   
> +   /* Specify the same binary preference to spawn the shell as the
> +      exec binary.  This avoids spawning a 64bit shell while debugging
> +      a 32bit program, which may confuse gdb.
> +      Also, this slightly breaks internal layers as we suppose the binary
> +      is Mach-O.  Doesn't harm in practice.  */
> +   if (exec_bfd != NULL)
> +     {
> +       cpu_type_t pref;
> +       size_t ocount;
> + 
> +       pref = bfd_mach_o_get_data (exec_bfd)->header.cputype;
> +       res = posix_spawnattr_setbinpref_np (&attr, 1, &pref, &ocount);
> +       if (res != 0 || ocount != 1)
> + 	fprintf_unfiltered (gdb_stderr, "Cannot set posix_spawn binpref\n");
> +     }
> + 
>     posix_spawnp (NULL, argv[0], NULL, &attr, argv, env);
>   }
>   

Tristan,
   This almost fixes the bug for the i386-apple-darwin10 build. However, while this
eliminates the failures when debugging i386 executables in the i386 darwin build of gdb 7.4,
it still results in the following failure when debugging x86_64 executables in the
same i386 darwin build of gdb...

% clang -arch x86_64 -g himenoBMTxpa.c
% file ./a.out
./a.out: Mach-O 64-bit executable x86_64
% fsf-gdb ./a.out
GNU gdb (GDB) 7.4
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i386-apple-darwin10.8.0".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...

warning: A handler for the OS ABI "Darwin" is not built into this configuration
of GDB.  Attempting to continue with the default i386:x86-64 settings.

Reading symbols from /Users/howarth/a.out...Reading symbols from
/Users/howarth/a.out.dSYM/Contents/Resources/DWARF/a.out...done.
done.
(gdb) break main
Breakpoint 1 at 0xd80: file himenoBMTxpa.c, line 71.
(gdb) r
Starting program: /Users/howarth/a.out 
darwin_set_sstep: unknown flavour: 4
Error calling thread_get_state for GP registers for thread 0x5379lxwarning:
Mach error at "i386-darwin-nat.c:118" in function
"i386_darwin_fetch_inferior_registers": (os/kern) invalid argument (0x4)
(gdb)

Thanks for your efforts in fixing this.
            Jack