Re: [Qemu-devel] [PATCH] HACKING: document #include order

[Eric Blake]

On 11/15/2016 02:29 PM, Stefan Hajnoczi wrote:
> It was not obvious to me why "qemu/osdep.h" must be the first #include.
> This documents the rationale and the overall #include order.
> 
> Cc: Fam Zheng <address@hidden>
> Cc: Markus Armbruster <address@hidden>
> Cc: Eric Blake <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  HACKING | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 

> +1.2. Include directives
> +
> +Order include directives as follows:
> +
> +#include "qemu/osdep.h"  /* Always first... */
> +#include <...>           /* then system headers... */
> +#include "..."           /* and finally QEMU headers. */
> +
> +The "qemu/osdep.h" header contains preprocessor macros that affect the 
> behavior
> +of core system headers like <stdint.h>.  It must be the first include so that
> +core system headers included by external libraries get the preprocessor 
> macros
> +that QEMU depends on.

Might be worth mentioning that only .c files include osdep.h (.h files
do not need to, because they can only be included by a .c file that has
already included osdep.h first).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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