Re: [PATCH v2 01/13] compiler.h: replace QEMU_GNUC_PREREQ macro

[Peter Maydell]

On Thu, 26 Nov 2020 at 11:29, <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Replace it with glib G_GNUC_CHECK_VERSION.
>
> Available since 2.42, the macro received a small correction in
> 2.55.1 (glib d44afbadda8a "macros: make G_GNUC_CHECK_VERSION()
> portable" which was apparently harmless).
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  include/qemu/atomic.h      |  2 +-
>  include/qemu/compiler.h    | 15 +++------------
>  scripts/cocci-macro-file.h |  1 -
>  accel/tcg/cpu-exec.c       |  2 +-
>  4 files changed, 5 insertions(+), 15 deletions(-)
>
> diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
> index c1d211a351..c409257c11 100644
> --- a/include/qemu/atomic.h
> +++ b/include/qemu/atomic.h
> @@ -248,7 +248,7 @@
>   * 4.3 (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36793).
>   */
>  #if defined(__i386__) || defined(__x86_64__)
> -#if !QEMU_GNUC_PREREQ(4, 4)
> +#if !G_GNUC_CHECK_VERSION(4, 4)
>  #if defined __x86_64__
>  #define smp_mb()    ({ asm volatile("mfence" ::: "memory"); (void)0; })
>  #else
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index c76281f354..cf044bab4a 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -7,21 +7,12 @@
>  #ifndef COMPILER_H
>  #define COMPILER_H
>
> +#include "glib-compat.h"

osdep.h already includes glib-compat.h, so if it's safe to
include it this early we should just move that #include line
in osdep.h up above compiler.h. But I don't think it's going
to be quite that simple, because some parts of osdep.h
need to happen before we include any system headers, and
glib-compat.h includes some system headers. As it stands
this fragment will pull in glib-compat.h too early.

You probably need to rearrange osdep.h so it is
 * config-host.h
 * poison.h
 * bits that must go before any standard headers
 * pure system includes
 * glib-compat.h
 * compiler.h
(and hopefully none of the above needed stuff set up by compiler.h !)

Or if this tangle of bits depending on each other seems too
messy, we could just leave QEMU_GNUC_PREREQ the way it is :-)

thanks
-- PMM