From: xu xin <xu.xin16@zte.com.cn>

When HOST CC = gcc (GCC) 4.8.5, we found that there is an error occurring:
Undefined __has_attribute as we built the whole kernel and tools.

To solve this, this patch is given to keep the compatibility with older
GCC versions.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Co-developed-by: wangyong <wang.yong12@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 tools/include/linux/compiler-gcc.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/include/linux/compiler-gcc.h b/tools/include/linux/compiler-gcc.h
index 8816f06fc6c7..333ed16b3b12 100644
--- a/tools/include/linux/compiler-gcc.h
+++ b/tools/include/linux/compiler-gcc.h
@@ -16,6 +16,10 @@
 # define __fallthrough __attribute__ ((fallthrough))
 #endif
 
+#ifndef __has_attribute
+# define __has_attribute(x) 0  /* Compatibility with GCC versions < 5.x */
+#endif
+
 #if __has_attribute(__error__)
 # define __compiletime_error(message) __attribute__((error(message)))
 #endif
-- 
2.25.1

From: cgel.zte@gmail.com
Date: Sun,  2 Jan 2022 12:02:01 +0000

> From: xu xin <xu.xin16@zte.com.cn>
> 
> When HOST CC = gcc (GCC) 4.8.5, we found that there is an error occurring:
                           ^^^^^

From [0]:

Program  Minimal version
GNU C    5.1

This applies to both HOSTCC and CC.

> Undefined __has_attribute as we built the whole kernel and tools.
> 
> To solve this, this patch is given to keep the compatibility with older
> GCC versions.
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Co-developed-by: wangyong <wang.yong12@zte.com.cn>
> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> ---
>  tools/include/linux/compiler-gcc.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/include/linux/compiler-gcc.h b/tools/include/linux/compiler-gcc.h
> index 8816f06fc6c7..333ed16b3b12 100644
> --- a/tools/include/linux/compiler-gcc.h
> +++ b/tools/include/linux/compiler-gcc.h
> @@ -16,6 +16,10 @@
>  # define __fallthrough __attribute__ ((fallthrough))
>  #endif
>  
> +#ifndef __has_attribute
> +# define __has_attribute(x) 0  /* Compatibility with GCC versions < 5.x */
> +#endif
> +
>  #if __has_attribute(__error__)
>  # define __compiletime_error(message) __attribute__((error(message)))
>  #endif
> -- 
> 2.25.1

[0] https://elixir.bootlin.com/linux/v5.16-rc8/source/Documentation/process/changes.rst#L32

Al

> GNU C    5.1

> This applies to both HOSTCC and CC.

> > Undefined __has_attribute as we built the whole kernel and tools.
> > 
> > To solve this, this patch is given to keep the compatibility with older
> > GCC versions.

Yes, but I think this error is a little unfriendly to users using a 
lower version of host GCC when cross compiling. 

Perhaps "#if gcc_version > = 51000" could be added to avoid the error 
'Undefined __has_attribute' 

or we can add `#error "hostcc don't support _has_attribute` to remind
the user of the cause of the error.

Or just use my previous patch.

I hope we can do something here to promote the situation as Nathan talked
before:

https://lore.kernel.org/all/91B93D4D-BEC8-4ACD-B71F-27C54D8B1B78@kernel.org/