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From: Markus Armbruster <armbru@redhat.com>
References: <1485879287-12548-1-git-send-email-peter.maydell@linaro.org>
Date: Tue, 31 Jan 2017 18:40:13 +0100
In-Reply-To: <1485879287-12548-1-git-send-email-peter.maydell@linaro.org>
	(Peter Maydell's message of "Tue, 31 Jan 2017 16:14:47 +0000")
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Subject: Re: [Qemu-devel] [PATCH] Drop QEMU_GNUC_PREREQ() checks for gcc
 older than 4.1
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, qemu-trivial@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, patches@linaro.org

Peter Maydell <peter.maydell@linaro.org> writes:

> We already require gcc 4.1 or newer (for the atomic
> support), so the fallback codepaths for older gcc
> versions than that are now dead code and we can
> just delete them.
>
> NB: clang reports itself as gcc 4.2 (regardless of
> clang version), so clang won't be using the fallbacks
> either.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> For compatibility with clang we should probably try to avoid
> using QEMU_GNUC_PREREQ() and instead have something in
> compiler.h that abstracts away whether the test for "does
> the compiler support feature foo" is via a GCC version
> check or a clang __has_feature or whatever.

Yes, testing for feature is better than testing a version.

This patch reduces use of QEMU_GNUC_PREREQ roughly by half.  Good.

>
>
>  include/qemu/compiler.h   |   8 ---
>  include/qemu/host-utils.h | 121 ----------------------------------------------
>  tcg/arm/tcg-target.h      |   7 ---
>  3 files changed, 136 deletions(-)
>
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index 157698b..fc12e49 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -24,17 +24,9 @@
>  
>  #define QEMU_NORETURN __attribute__ ((__noreturn__))
>  
> -#if QEMU_GNUC_PREREQ(3, 4)
>  #define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
> -#else
> -#define QEMU_WARN_UNUSED_RESULT
> -#endif

Should we inline this macro?

>  
> -#if QEMU_GNUC_PREREQ(4, 0)
>  #define QEMU_SENTINEL __attribute__((sentinel))
> -#else
> -#define QEMU_SENTINEL
> -#endif

Likewise.

>  
>  #if QEMU_GNUC_PREREQ(4, 3)
>  #define QEMU_ARTIFICIAL __attribute__((always_inline, artificial))
[Nothing to say on the rest...]

Regardless of my question:
Reviewed-by: Markus Armbruster <armbru@redhat.com>