Re: [Pgubook-readers] (no subject)

[Bryn M. Reeves]

On 05/20/2013 07:42 AM, Kanish Katariya wrote:
>      I am reading programmin ground up book on assembly langauge and I
> have a doubt,which I am unable to pass.
> The first program in chapter 3 in which we just exit, I found that
> inserting tha max 32bit value in the %ebx register and it is replying
> 255 instead of the maximum value(4294967296), when I enter the 'echo $?'
> Command in terminal. Plz clear my doubt why it is repliying different
> number.

The definition of the POSIX wait(2) function limits the size of the 
return code portion of the status field to 8-bits:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/wait.html

WEXITSTATUS(stat_val)

    If the value of WIFEXITED(stat_val) is non-zero, this macro 
evaluates to the low-order 8 bits of the status argument that the child 
process passed to _exit() or exit(), or the value the child process 
returned from main().

So what you're seeing here is truncation of the value passed by the 
program (to fit in the low order 8-bit field of the status word).

In effect all POSIX exit status are (value % 256).

Regards,
Bryn.