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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 13 Nov 2018 18:07:58 +0000
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Subject: Re: [Qemu-devel] [PATCH 02/13] target: arm: Remove unused headers
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To: =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= <philmd@redhat.com>
Cc: Samuel Ortiz <sameo@linux.intel.com>, QEMU Developers <qemu-devel@nongnu.org>, Richard Henderson <richard.henderson@linaro.org>, qemu-arm <qemu-arm@nongnu.org>

On 13 November 2018 at 18:02, Philippe Mathieu-Daud=C3=A9 <philmd@redhat.co=
m> wrote:
> On 13/11/18 18:01, Peter Maydell wrote:
>>
>> On 13 November 2018 at 16:52, Samuel Ortiz <sameo@linux.intel.com> wrote=
:

>>> --- a/target/arm/helper.c
>>> +++ b/target/arm/helper.c
>>> @@ -12,13 +12,10 @@
>>>   #include "internals.h"
>>>   #include "exec/gdbstub.h"
>>>   #include "exec/helper-proto.h"
>>> -#include "qemu/host-utils.h"
>>
>>
>> This is for muldiv64().
>
>
> But it is already included by "cpu.h" -> "exec/cpu-defs.h"

> So they are not "unused" but "unnecessary".
>
> I thought this would be better to clean this once, before Samuel split.

Generally I think that if a .c file directly uses function X declared in
header Y it should #include Y, even if it happens that it already includes
other header Z that includes Y. Otherwise if we refactor Z later such
that it no longer needs to include Y, it will break compilation of the .c
file. (That is, Z including Y is a detail of the implementation of Z,
not a guarantee made by Z to its users.)

The exception here is where the header guarantees that it's going
to include certain other things (which is the case for eg our osdep.h).

thanks
-- PMM