Re: Ping: [patch] general updates and improvements to QNX NTO support

[Kris Warkentin <kewarken at qnx dot com>]

Mark Kettenis wrote:

> Ah, OK.  Sorry, I misread that.
>
>

No problem...kind of a funny looking diff.

>   I also changed the macro defines so that I can assign and test.  ie.
>
>   old:
>   define nto_regset_fill(regset, data) 
(*current_nto_target.nto_regset_fill) (regset, data)
>
>   new:
>   #define nto_regset_fill (current_nto_target.nto_regset_fill)
>
>   That way I can easily switch targets in code.
>
> Hmm.  In that case wouldn't it be better to turn current_nto_target
> into a pointer, and having a `struct nto_target_ops' for each target
> such that you can switch targets by simply doing a pointer assignment?
> That would probably get rid of all the macros.
>
>

That's a good idea and I actually do something very similar in our 
remote support (which I haven't submitted yet)  As it stands, rather 
than just switching a pointer, I initialize all the members in 
init_i386nto_ops.  I have similar init functions for arm, sh, mips and 
ppc.  I'm not sure how I'd get rid of the macros though....it's still 
convenient to have a generic nto_regset_fill function macro rather than 
having to dereference.  Plus, it's handy to be able to check for 
validity before using a function like in nto_elf_osabi_sniffer.  I'm 
just thinking that if gdb were truly multi-arched, there could be a 
situation where my nto_target_ops haven't been initialized and something 
like a sniffer could crash.  I could be wrong about that though.

>   I am defining current_nto_target in nto-tdep.h as being extern but 
I   don't declare it there.  Is having a global verboten?  I has assumed 
it   was okay since we have many precedents like inferior_ptid and 
current_target and such.
>
> Declaring variables as `extern' in a header file is fine, although you
> should avoid globals if as much as possible.
>

I did it that way to be consistent with the current_target idea within 
gdb.  We actually have five targets so it makes it easier to switch 
things around.  I'd welcome any ideas for improvement though.  Not much 
originality on all this - I pretty much tried to do things exactly the 
way target.h does.  I hope I don't lose marks for plaigarism... ;-)

cheers,

Kris