Re: libc-mini.a or libmes-builtins.a should also include integer division algorithm ?

[Danny Milosavljevic]

> For comparison, GCC just emits a SIGFPE signal on division by zero (I've 
> tried).  That would mean that signal emission (or syscalls in general) would 
> have to be builtin, too.  But I guess that would be OK.

Some more details on what different compilers do:

http://www.keil.com/support/man/docs/armcc/armcc_chr1359124235078.htm ... wow, 
complicated.

>__rt_raise(SIGFPE, DIVBYZERO)

And another:

https://stackoverflow.com/questions/6744453/how-to-track-down-a-sigfpe-arithmetic-exception?rq=1

>    3 raise()  0x402720ac   
>    2 __aeabi_uldivmod()  0x400bb0b8    
>    1 __divsi3()  0x400b9880

>    Integer division-by-zero errors can be trapped and identified by 
> re-implementing the appropriate C library helper functions. The default 
> behavior when division by zero occurs is that when the signal function is 
> used, or __rt_raise() or __aeabi_idiv0() are re-implemented, __aeabi_idiv0() 
> is called. Otherwise, the division function returns zero. __aeabi_idiv0() 
> raises SIGFPE with an additional argument, DIVBYZERO.

And to raise we'd use in mes:

int
raise (int signum)
{
  return _sys_call2 (SYS_kill, (long) getpid(), (long) signum);
}

pid_t
getpid ()
{
  return _sys_call (SYS_getpid);
}

That's not so bad...

(lib/linux/getpid.c and lib/posix/raise.c)

But still, would be easier just not to implement a default div0 handler and 
have the user or libc supply one--at least at first.

pgpg9lQqTpvoV.pgp
Description: OpenPGP digital signature