Re: [PING2] : [RFC/RFA] PING: skip __main

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> Date: Thu, 5 Jun 2008 16:26:40 -0400
> From: Daniel Jacobowitz <drow@false.org>
> 
> On Sat, May 31, 2008 at 08:46:25AM +0200, Pierre Muller wrote:
> >   Should I use the 32bit typecast strategy:
> > 
> > unsigned int32 pc_after = pc + 5; 
> > unsigned int32 depl = extract_unsigned_integer (buf, 4);
> >    
> > unsigned int32 dest = pc_after - depl;
> > pc = dest;
> > 
> > I don't know the checks done in C,
> > are there any overflow checks in code like this,
> > or is it safe to assume that it will work,
> > even on machine that perform their operations
> > on more than 32 bits?
> 
> If you use uint32_t, then you are guaranteed wrapping at 32 bits.
> So that is probably the best thing to do.  See the patch I just posted
> to make stdint.h available everywhere.

The diff should use extract_signed_integer().

I'm not sure if the wrapping is actually necessary.  Does the
assembler/linker actually depend on it?  Or does it error out on such
large jumps?  If so, alternatively you could explicity truncate the
generated address to 32 bits using & 0xffffffffU.