implicit declaration of function 'pipe2'

[bukepo]

commit: 88780da9141b6bb4476f476fdd736590328378e0
log:

ot-commissioner/repo/third_party/libevent/repo/evutil.c:2638:6: warning: implicit declaration of function 'pipe2' is invalid in C99 [-Wimplicit-function-declaration]
        if (pipe2(fd, O_NONBLOCK|O_CLOEXEC) == 0)
            ^
1 warning generated.

[wgtdkp]

notice that this warning comes from the third_party libevent. I tend to let it be.

FYI, we are not using the latest libevent to be compatible with Android.
There are more platform-specific libevent warnings from on my workstation:

☁  ot-commissioner [main] ⚡  cmake --build build
[67/180] Building C object third_party/libevent/repo/CMakeFiles/event_core_static.dir/evutil_rand.c.o
In file included from ../third_party/libevent/repo/./arc4random.c:64,
                 from ../third_party/libevent/repo/evutil_rand.c:134:
/usr/include/x86_64-linux-gnu/sys/sysctl.h:21:2: warning: #warning "The <sys/sysctl.h> header is deprecated and will be removed." [-Wcpp]
   21 | #warning "The <sys/sysctl.h> header is deprecated and will be removed."
      |  ^~~~~~~
In file included from ../third_party/libevent/repo/evutil_rand.c:134:
../third_party/libevent/repo/./arc4random.c: In function ‘arc4_seed_sysctl_linux’:
../third_party/libevent/repo/./arc4random.c:191:3: warning: ‘sysctl’ is deprecated [-Wdeprecated-declarations]
  191 |   if (0 != sysctl(mib, 3, &buf[len], &n, NULL, 0))
      |   ^~
In file included from ../third_party/libevent/repo/./arc4random.c:64,
                 from ../third_party/libevent/repo/evutil_rand.c:134:
/usr/include/x86_64-linux-gnu/sys/sysctl.h:70:12: note: declared here
   70 | extern int sysctl (int *__name, int __nlen, void *__oldval,
      |            ^~~~~~
[180/180] Linking CXX executable tests/commissioner-test

[bukepo]

Can _GNU_SOURCE suppress this warning?