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RE: [PATCH] btrace: support 32-bit inferior on 64-bit host


> -----Original Message-----
> From: Pedro Alves [mailto:palves@redhat.com]
> Sent: Monday, March 2, 2015 11:08 PM
> To: Metzger, Markus T
> Cc: gdb-patches@sourceware.org; Jan Kratochvil
> Subject: Re: [PATCH] btrace: support 32-bit inferior on 64-bit host


> > Use the machine field in struct utsname provided by a uname call to
> > determine whether we are running on a 64-bit host.
> 
> Does this correctly handle the case of 32-bit GDB on 64-bit system
> debugging _32-bit_ inferior?  Based on e.g..
> 
>  $ uname -m
>  x86_64
>  $ i386 uname -m
>  i686
> 
> I'd guess "no".

The man page of i386 (setarch) says:

      "This utility currently only affects the output of uname -m.  For  example,  on  an
       AMD64  system,  running  'setarch i386 program' will cause 'program' to see i686 (or other
       relevant arch) instead of x86_64 as machine type."

When I compile GDB on a 32-bit system and then run it on a 64-bit system, the uname
call reports "x86_64".

When I run GDB under i386, this changes to "i686" - no matter where I built GDB.

I'd say it is working for our purpose.

Regards,
Markus.

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