Re: [Qemu-devel] [PATCH] target_posix_types.h

[Thayne Harbaugh]

On Wed, 2007-11-14 at 19:32 +0100, Fabrice Bellard wrote:
> Thayne Harbaugh wrote:
> > This patch, 44_target_posix_types.patch provides target specific posix
> > types.  These types improve target structure creation, code similarity
> > to kernel code and improve type casting for assignment between target
> > and host.
> 
> Why is it needed ?


It's not *necessary*, but it makes code more readable and it simplifies
having to always check for what a typedef on a target might map to.  It
makes target structures more comparable to their structures in the
kernel.

A simple example:

struct target_timeval {
    abi_long tv_sec;
    abi_long tv_usec;
};

vs.

struct target_timeval {
    target_time_t tv_sec;
    target_suseconds_t tv_usec;
};


It also makes type conversion between target and host more obvious.

It also means that more code can be shared rather than #ifdef'ed when
targets differ on their base definitions.

It's just another level of abstraction, we can always stick with
abi_long, abi_ulong, etc..  I've just noticed that size and sign
handling when converting between target and host are a common source of
errors and this simplifies things.  We use it in all our patches and it
has helped simplify and fix errors.