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

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

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"

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