[kvm-unit-tests PATCH] compiler: use __builtin_add_overflow_p for gcc >= 7.1.0

[kvm-unit-tests PATCH] compiler: use __builtin_add_overflow_p for gcc >= 7.1.0

[Po-Hsu Lin]

Compilation on Ubuntu Xenial 4.4.0-210-generic i386 with gcc version 5.4.0
20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.12) will fail with:
  lib/linux/compiler.h:37:34: error: implicit declaration of function
    ‘__builtin_add_overflow_p’ [-Werror=implicit-function-declaration]

From the GCC document[1] it looks like this built-in function was only
introduced since 7.1.0

This can be fixed by simply changing the version check from 5.1.0 to 7.1.0

[1] https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/Integer-Overflow-Builtins.html

Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
---
 lib/linux/compiler.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/linux/compiler.h b/lib/linux/compiler.h
index 745792a..5d9552a 100644
--- a/lib/linux/compiler.h
+++ b/lib/linux/compiler.h
@@ -30,7 +30,7 @@
 	__builtin_mul_overflow(a, b, &__d);		\
 })
 #endif
-#elif GCC_VERSION >= 50100
+#elif GCC_VERSION >= 70100
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #define check_add_overflow(a, b) __builtin_add_overflow_p(a, b, (typeof((a) + (b)))0)
 #define check_sub_overflow(a, b) __builtin_add_overflow_p(a, b, (typeof((a) - (b)))0)
-- 
2.25.1

Re: [kvm-unit-tests PATCH] compiler: use __builtin_add_overflow_p for gcc >= 7.1.0

[Andrew Jones]

On Wed, Jun 02, 2021 at 04:24:43PM +0800, Po-Hsu Lin wrote:
> Compilation on Ubuntu Xenial 4.4.0-210-generic i386 with gcc version 5.4.0
> 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.12) will fail with:
>   lib/linux/compiler.h:37:34: error: implicit declaration of function
>     ‘__builtin_add_overflow_p’ [-Werror=implicit-function-declaration]
> 
> From the GCC document[1] it looks like this built-in function was only
> introduced since 7.1.0
> 
> This can be fixed by simply changing the version check from 5.1.0 to 7.1.0
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/Integer-Overflow-Builtins.html
> 
> Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
> ---
>  lib/linux/compiler.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/linux/compiler.h b/lib/linux/compiler.h
> index 745792a..5d9552a 100644
> --- a/lib/linux/compiler.h
> +++ b/lib/linux/compiler.h
> @@ -30,7 +30,7 @@
>  	__builtin_mul_overflow(a, b, &__d);		\
>  })
>  #endif
> -#elif GCC_VERSION >= 50100
> +#elif GCC_VERSION >= 70100
>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>  #define check_add_overflow(a, b) __builtin_add_overflow_p(a, b, (typeof((a) + (b)))0)
>  #define check_sub_overflow(a, b) __builtin_add_overflow_p(a, b, (typeof((a) - (b)))0)
> -- 
> 2.25.1
>

Reviewed-by: Andrew Jones <drjones@redhat.com>