Re: tidying up osdep.h

[Markus Armbruster]

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 4/14/21 9:17 PM, Peter Maydell wrote:
>> (cc'ing people related to the recent 'extern "C"' patches and also
>> randomly Markus as somebody who's had opinions on header cleanups
>> in the past...)
>> 
>> osdep.h as it stands today is a mix of two things:
>>  (1) it has the "must be included by everybody" items:
>>    (a) config-host.h, poison.h, compiler.h
>>    (b) things which must be done before any system header is included
>>        (like defining __STDC_CONSTANT_MACROS or WIN32_LEAN_AND_MEAN)
>>    (c) includes of system headers which we need to then fix up for
>>        portability issues (eg redefining assert on mingw, defining
>>        fallback versions of missing macros)
>>  (2) it has declarations for a library of QEMU functions, some of which
>>      typically wrap and abstract away OS specifics (like qemu_create(),
>>      qemu_unlink()), and some of which seem to have just been dumped
>>      in here for convenience (like qemu_hw_version())
>> 
>> Every file needs (1), which is why we mandate osdep.h as the first
>> include; most files don't need a lot of the things in (2) (for instance
>> qemu_hw_version() is used in just half a dozen .c files). Is it worth
>> trying to split some of the type (2) items out into their own header files?
>> 
>> I suspect that the advantages would be primarily just making osdep.h
>> a bit clearer to read and less of an "attractive nuisance" for new
>> additions; I imagine the bulk of the extra compilation time represented
>> by osdep.h is going to be because it pulls in dozens of system
>> headers, most of which are going to be required under heading (1).
>
> What about:
>
> - extract qemu_hw_version() to "qemu/legacy_api.h"?
>
> - extract (1) from osdep.h as osinc.h (because described as
>   "OS includes and handling of OS dependencies")?
>   Or KISS as "qemu-first-include.h"...

For what it's worth, the autoconf convention is to call it "config.h".

> - osdep.h now contains the declarations for osdep.c
>
> Regards,
>
> Phil.