[PATCH bpf-next v2] tools/bpf: make libbpf _GNU_SOURCE friendly

[PATCH bpf-next v2] tools/bpf: make libbpf _GNU_SOURCE friendly

[Yonghong Song]

During porting libbpf to bcc, I got some warnings like below:
  ...
  [  2%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf.c.o
  /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf.c:12:0:
  warning: "_GNU_SOURCE" redefined [enabled by default]
   #define _GNU_SOURCE
  ...
  [  3%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf_errno.c.o
  /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c: In function ‘libbpf_strerror’:
  /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c:45:7:
  warning: assignment makes integer from pointer without a cast [enabled by default]
     ret = strerror_r(err, buf, size);
  ...

bcc is built with _GNU_SOURCE defined and this caused the above warning.
This patch intends to make libpf _GNU_SOURCE friendly by
  . define _GNU_SOURCE in libbpf.c unless it is not defined
  . undefine _GNU_SOURCE as non-gnu version of strerror_r is expected.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/lib/bpf/libbpf.c       | 2 ++
 tools/lib/bpf/libbpf_errno.c | 1 +
 2 files changed, 3 insertions(+)

Changelog:
 v1 -> v2:
   . undef _GNU_SOURCE instead of multiversioning strerror_r,
     suggested by Jakub.

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ed4212a4c5f9..59b748ebd15f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9,7 +9,9 @@
  * Copyright (C) 2017 Nicira, Inc.
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c
index d83b17f8435c..4343e40588c6 100644
--- a/tools/lib/bpf/libbpf_errno.c
+++ b/tools/lib/bpf/libbpf_errno.c
@@ -7,6 +7,7 @@
  * Copyright (C) 2017 Nicira, Inc.
  */
 
+#undef _GNU_SOURCE
 #include <stdio.h>
 #include <string.h>
 
-- 
2.17.1

Re: [PATCH bpf-next v2] tools/bpf: make libbpf _GNU_SOURCE friendly

[Jakub Kicinski]

On Thu, 29 Nov 2018 15:31:45 -0800, Yonghong Song wrote:
> During porting libbpf to bcc, I got some warnings like below:
>   ...
>   [  2%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf.c.o
>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf.c:12:0:
>   warning: "_GNU_SOURCE" redefined [enabled by default]
>    #define _GNU_SOURCE
>   ...
>   [  3%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf_errno.c.o
>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c: In function ‘libbpf_strerror’:
>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c:45:7:
>   warning: assignment makes integer from pointer without a cast [enabled by default]
>      ret = strerror_r(err, buf, size);
>   ...
> 
> bcc is built with _GNU_SOURCE defined and this caused the above warning.
> This patch intends to make libpf _GNU_SOURCE friendly by
>   . define _GNU_SOURCE in libbpf.c unless it is not defined
>   . undefine _GNU_SOURCE as non-gnu version of strerror_r is expected.
> 
> Signed-off-by: Yonghong Song <yhs@fb.com>

Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>

FWIW :)

Re: [PATCH bpf-next v2] tools/bpf: make libbpf _GNU_SOURCE friendly

[Daniel Borkmann]

On 11/30/2018 12:47 AM, Jakub Kicinski wrote:
> On Thu, 29 Nov 2018 15:31:45 -0800, Yonghong Song wrote:
>> During porting libbpf to bcc, I got some warnings like below:
>>   ...
>>   [  2%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf.c.o
>>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf.c:12:0:
>>   warning: "_GNU_SOURCE" redefined [enabled by default]
>>    #define _GNU_SOURCE
>>   ...
>>   [  3%] Building C object src/cc/CMakeFiles/bpf-shared.dir/libbpf/src/libbpf_errno.c.o
>>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c: In function ‘libbpf_strerror’:
>>   /home/yhs/work/bcc2/src/cc/libbpf/src/libbpf_errno.c:45:7:
>>   warning: assignment makes integer from pointer without a cast [enabled by default]
>>      ret = strerror_r(err, buf, size);
>>   ...
>>
>> bcc is built with _GNU_SOURCE defined and this caused the above warning.
>> This patch intends to make libpf _GNU_SOURCE friendly by
>>   . define _GNU_SOURCE in libbpf.c unless it is not defined
>>   . undefine _GNU_SOURCE as non-gnu version of strerror_r is expected.
>>
>> Signed-off-by: Yonghong Song <yhs@fb.com>
> 
> Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> 
> FWIW :)
> 

Applied, thanks.