netdev - Re: [PATCH net-next 1/2] tools lib bpf: suppress useless include

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Date:	Mon, 15 Aug 2016 11:20:39 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Eric Leblond <eric@...it.org>, <netdev@...r.kernel.org>
CC:	Alexei Starovoitov <ast@...com>
Subject: Re: [PATCH net-next 1/2] tools lib bpf: suppress useless include



On 2016/8/13 20:17, Eric Leblond wrote:
> The include of err.h is not explicitely needed in exported
> functions and it was causing include conflict with some existing
> code due to redefining some macros.
>
> Signed-off-by: Eric Leblond <eric@...it.org>
> ---
>   tools/lib/bpf/libbpf.c | 1 +
>   tools/lib/bpf/libbpf.h | 1 -
>   2 files changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b699aea..7872ff6 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -31,6 +31,7 @@
>   #include <linux/kernel.h>
>   #include <linux/bpf.h>
>   #include <linux/list.h>
> +#include <linux/err.h>
>   #include <libelf.h>
>   #include <gelf.h>
>   
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index dd7a513..a6c5cde 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -23,7 +23,6 @@
>   
>   #include <stdio.h>
>   #include <stdbool.h>
> -#include <linux/err.h>
>   

Functions declared in this header require PTR_ERR
to decode error number. Logically speaking, this
header depends linux/err.h, so this include is
required. If not, there must have another way for
caller to decode error numbers.

I know the problem you try to solve. Please have a look at thread

https://lkml.org/lkml/2015/12/17/20

At that time I think we should create a wrapper in libbpf.h like this:

#ifdef USE_LINUX_ERR
#include <linux/err.h>
#endif
...
int libbpf_ptr_err(void *ptr);
...

It is acceptable but ugly. Can you find a better method?

Thank you.

>   enum libbpf_errno {
>   	__LIBBPF_ERRNO__START = 4000,