gdb print /x always big endian order?

gdb print /x always big endian order?

[J K]

 Hello,

 I've used a simple code to examine the storage
 of a short on a big and little endian machine.

 It seems in GNU gdb Red Hat Linux (5.1-1) when
 I do a print /x the order is Big Endian regardless
 of the host architecture. Just wondering if this
 is expected, I didn't see anything in the docs.

    short short_val = 31415;
    unsigned char buff[8];
    memcpy(buff,&short_val,2);
    printf("Short bytes 0x%x 0x%x\n",buff[0],buff[1]);
  
 on Little Endian machine:
    Short bytes 0xb7 0x7a  

 on Big Endian machine: 
    Short bytes 0x7a 0xb7  

  On the Little Endian machine in gdb:
(gdb) p short_val
$18 = 31415
(gdb) p /x short_val
$19 = 0x7ab7           <- not what I expected.
(gdb) x/2xb &short_val
0xbffff82a:     0xb7    0x7a
(gdb) x/2ub &short_val
0xbffff82a:     183     122 
  
  Memory is in the order I would expect but the
  print /x shows the order as Big Endian.
  
  Thanks,
  J.K.

   





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Re: gdb print /x always big endian order?

[Daniel Jacobowitz]

On Thu, Feb 05, 2004 at 10:00:42AM -0800, J K wrote:
> 
>  Hello,
> 
>  I've used a simple code to examine the storage
>  of a short on a big and little endian machine.
> 
>  It seems in GNU gdb Red Hat Linux (5.1-1) when
>  I do a print /x the order is Big Endian regardless
>  of the host architecture. Just wondering if this
>  is expected, I didn't see anything in the docs.

Yes, this is expected.  Consider:

>     short short_val = 31415;

What would C do if you said short_val = 0x7ab7?

>  on Little Endian machine:
>     Short bytes 0xb7 0x7a  

Precisely the same thing :)

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Re: gdb print /x always big endian order?

[Andreas Schwab]

J K <ellips@yahoo.com> writes:

>  It seems in GNU gdb Red Hat Linux (5.1-1) when
>  I do a print /x the order is Big Endian regardless
>  of the host architecture.

The print command just prints a value, and values don't have endianess.
Only memory contents have.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: gdb print /x always big endian order?

[Bill Gatliff]

JK: 


Indeed.  If you want to see endianness, use 'x' instead, and ask it for a 
string of hex bytes.  :^) 


b.g. 


Andreas Schwab writes: 

> J K <ellips@yahoo.com> writes: 
> 
>>  It seems in GNU gdb Red Hat Linux (5.1-1) when
>>  I do a print /x the order is Big Endian regardless
>>  of the host architecture.
> 
> The print command just prints a value, and values don't have endianess.
> Only memory contents have. 
> 
> Andreas. 
> 
> -- 
> Andreas Schwab, SuSE Labs, schwab@suse.de
> SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
> Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."
 


 --
Bill Gatliff
Embedded GNU, Linux training and development.
bgat@billgatliff.com