Re: [Qemu-devel] [PATCH 00/12] qemu-common.h/osdep.h refactoring

[Daniel P. Berrange]

On Wed, Jul 22, 2015 at 05:43:59PM +0100, Peter Maydell wrote:
> This series makes a start at cleaning up some of our headers
> to avoid the common problem of header files including qemu-common.h
> (which then in turn can lead to awkward circular includes).
> 
> One common cause of this is that we don't have any header
> which will include the basic things most header files require,
> except for qemu-common.h. This series fixes that by making
> 'osdep.h' that "common basic stuff" header. The idea is that:
>  * osdep.h can be included from anywhere, since it doesn't
>    include any other QEMU headers itself except a few very
>    restricted special purpose ones (config-host.h, compiler.h, etc)
>  * osdep.h provides:
>    + things everybody needs, like NULL, int32_t, container_of,
>      the CONFIG_* defines, etc
>    + things that will cause subtle problems if they're not
>      present everywhere (eg directly using system headers and
>      not getting the portability fixups will result in something
>      that builds on most but not all hosts)
> 
> So most places can just include osdep.h, not the full qemu-common.h.
> 
> (I initially thought about defining a new header for this
> purpose, "qemu/basics.h" or some such, but in fact osdep.h
> was already very close to what I wanted so it didn't really
> seem like it was very useful to switch everything over.)
> 
> The series has some minor cleanups, some shuffling around of
> things between qemu-common.h, osdep.h and compiler.h, and
> a couple of patches at the end that use osdep.h to allow
> dropping a qemu-common.h include from various header files,
> as a demonstration.
> 
> The real question here I guess is whether people like the
> direction I'm trying to go with this. If so, we can further
> reduce the number of qemu-common.h includes without too much
> difficulty with further patches.

I broadly like the direction of this change. I think it is
probably worth being strict about requiring #include of
osdep.h as the first header in every .c file. And validating
such a rule programmatically at make check time or equiv.

Regards,
Daniel
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