Re: [Qemu-devel] [PATCH 03/15] hw/ssi: Remove SSIBus from "qemu/typedefs.h"

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 15/01/19 13:28, Markus Armbruster wrote:
>>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>> ---
>>>  hw/arm/strongarm.h      | 1 +
>>>  include/hw/arm/pxa.h    | 1 +
>>>  include/hw/ssi/pl022.h  | 1 +
>>>  include/hw/ssi/ssi.h    | 1 +
>>>  include/qemu/typedefs.h | 1 -
>>>  5 files changed, 4 insertions(+), 1 deletion(-)
>> When typedefs.h changes, we recompile the world, but it pretty much only
>> ever changes when new typedefs are added.  Thus, *keeping* a typedef
>> there is therefore pretty cheap.
>> 
>> Nevertheless, we shouldn't keep typedefs there without a real reason.
>> Being able to move one away without having to add any new #include
>> directives is a strong sign for "no real reason".  I like patches doing
>> that.
>> 
>> What I don't like is adding #include directives just so you can move
>> typedefs out of typedefs.h: it slows down the build.  Granted, the four
>
> (three - one added line is the typedef).

Correct.

>> added by this patch are a drop in the bucket.  The point I'm trying to
>> make is typedefs.h's purpose: it's for avoiding #include directives.
>> Circular ones in particular, but others, too.
>
> In this case, adding ssi.h inclusions to SSI controllers seems to be a
> feature, not a bug.

Adding #include can be a necessity.  It can't be a feature any more than
"slowing down your compiles" could be one :)

I'm particularly wary of unnecessary #include in headers.