Re: dangers of current NEED_CPU_H, CONFIG_SOFTMMU, CONFIG_USER_ONLY

[Claudio Fontana]

On 12/17/20 11:49 PM, Peter Maydell wrote:
> On Thu, 17 Dec 2020 at 22:45, Claudio Fontana <cfontana@suse.de> wrote:
>>
>> On 12/17/20 9:15 PM, Peter Maydell wrote:
>>> On Thu, 17 Dec 2020 at 19:46, Claudio Fontana <cfontana@suse.de> wrote:
>>> Yeah, don't try to ifdef out struct fields in common-compiled code...
>>
>> or should I? Using
>>
>> #ifdef NEED_CPU_H
>> #ifdef CONFIG_SOFTMMU
>>
>> seems to do what I expect. Is it wrong?
> 
> I think that gives you two versions of the struct:
> - one seen by compiled-once files and by compiled-per-target softmmu files
> - one seen by compiled-per-target user-only files
> 
> Since the user-only target executables link both compiled-per-target
> and compiled-once files I think they end up with different C files
> thinking the same struct has a different layout/size which seems
> like it's going to cause problems.
> 
> thanks
> -- PMM
> 

It doesn't with

#ifdef NEED_CPU_H
#ifdef CONFIG_SOFTMMU

just double checked the pointers from both files compiled per target and 
"common"; also all tests are ok.

It immediately breaks if I replace those two defines with #ifndef 
CONFIG_USER_ONLY and recompile.

I thought it was by design, but I guess this is just a "lucky" accident?

Ciao,

Claudio