Re: [PATCH v3 1/1] include: Don't include qemu/osdep.h

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jan 12, 2023 at 08:51:32AM -0500, Michael S. Tsirkin wrote:
> On Thu, Jan 12, 2023 at 12:50:05PM +0100, Markus Armbruster wrote:
> > docs/devel/style.rst mandates:
> > 
> >     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.
> > 
> >     Do not include "qemu/osdep.h" from header files since the .c file
> >     will have already included it.
> > 
> > A few violations have crept in.  Fix them.
> > 
> > Signed-off-by: Markus Armbruster <armbru@redhat.com>
> > Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
> > Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
> > Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> 
> With my awesome grep skillz I found one more:
> $ grep -r --include='*.h' qemu/osdep.h
> include/block/graph-lock.h:#include "qemu/osdep.h"

Also:
$ grep -r --include='*.inc' qemu/osdep.h
ui/vnc-enc-zrle.c.inc:#include "qemu/osdep.h"
crypto/akcipher-nettle.c.inc:#include "qemu/osdep.h"
crypto/akcipher-gcrypt.c.inc:#include "qemu/osdep.h"
crypto/rsakey-nettle.c.inc:#include "qemu/osdep.h"
crypto/cipher-gnutls.c.inc:#include "qemu/osdep.h"
target/xtensa/core-dc233c/xtensa-modules.c.inc:#include "qemu/osdep.h"
target/xtensa/core-sample_controller/xtensa-modules.c.inc:#include "qemu/osdep.h"
target/xtensa/core-de212/xtensa-modules.c.inc:#include "qemu/osdep.h"
target/xtensa/core-dc232b/xtensa-modules.c.inc:#include "qemu/osdep.h"
target/xtensa/core-fsf/xtensa-modules.c.inc:#include "qemu/osdep.h"
target/cris/translate_v10.c.inc:#include "qemu/osdep.h"



> Looks like all C files must include qemu/osdep.h, no?
> How about
> 
> 1- add -include qemu/osdep.h on compile command line
>    drop #include "qemu/osdep.h" from C files
> 2- drop double include guards, replace with a warning.
> 
> following patch implements part 2:
> 
> 
> qemu/osdep: don't include it from headers
> 
> doing so will lead to trouble eventually - instead of
> working around such cases make it more likely it will fail.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> ---
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 7d059ad526..e4a60f911c 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -24,7 +24,12 @@
>   * This work is licensed under the terms of the GNU GPL, version 2 or later.
>   * See the COPYING file in the top-level directory.
>   */
> -#ifndef QEMU_OSDEP_H
> +#ifdef QEMU_OSDEP_H
> +#warning "Never include qemu/osdep.h from a header!"
> +#endif
> +
> +static inline void qemu_osdep_never_include_from_header(void) {}
> +
>  #define QEMU_OSDEP_H
>  
>  #include "config-host.h"
> @@ -714,5 +719,3 @@ static inline int platform_does_not_support_system(const char *command)
>  #ifdef __cplusplus
>  }
>  #endif
> -
> -#endif