Re: [PATCH] selftests: proc: include fcntl.h in proc-pidns

[Amin Vakil <info@aminvakil.com>]

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On 6/18/26 6:54 PM, Shuah Khan wrote:
> On 6/18/26 09:14, Amin Vakil wrote:
>> proc-pidns.c uses open() and O_* flags, but does not include
>> <fcntl.h>. This breaks the proc selftests build with errors such as:
>>
>>    error: implicit declaration of function 'open'
>>    error: 'O_WRONLY' undeclared
>>    error: 'O_CREAT' undeclared
>>    error: 'O_RDONLY' undeclared
>>
>> Include <fcntl.h> to provide the declaration and flag definitions.
> 
> Did you install headers before compiling the test?

Sorry, no I hadn't.

But seems like problem is still relevant after make headers, I've tested 
now with these commands:

make -C tools/testing/selftests TARGETS=proc clean
make headers
make -C tools/testing/selftests TARGETS=proc
   CC       proc-pidns
proc-pidns.c: In function ‘touch’:
proc-pidns.c:34:18: error: implicit declaration of function ‘open’; did 
you mean ‘popen’? [-Wimplicit-function-declaration]
    34 |         int fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC, 0644);
       |                  ^~~~
       |                  popen
proc-pidns.c:34:29: error: ‘O_WRONLY’ undeclared (first use in this 
function)
    34 |         int fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC, 0644);
       |                             ^~~~~~~~
proc-pidns.c:34:29: note: each undeclared identifier is reported only 
once for each function it appears in
proc-pidns.c:34:38: error: ‘O_CREAT’ undeclared (first use in this function)
    34 |         int fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC, 0644);
       |                                      ^~~~~~~
proc-pidns.c: In function ‘ns_setup’:
proc-pidns.c:49:54: error: ‘O_RDONLY’ undeclared (first use in this 
function); did you mean ‘MS_RDONLY’?
    49 |         self->host_mntns = open("/proc/self/ns/mnt", 
O_RDONLY|O_CLOEXEC);
       |                                                      ^~~~~~~~
       |                                                      MS_RDONLY

After applying the patch I've sent, error is gone.

My environment if relevant:
$ gcc --version
gcc (GCC) 16.1.1 20260430
$ make --version
GNU Make 4.4.1
Built for x86_64-pc-linux-gnu
$ ldd --version
ldd (GNU libc) 2.43
$ getconf GNU_LIBC_VERSION
glibc 2.43
> 
>>
>> Fixes: 5554d820f71c ("selftests/proc: add tests for new pidns APIs")
>> Tested with:
>>    make -C tools/testing/selftests TARGETS=proc
>>
>> Signed-off-by: Amin Vakil <info@aminvakil.com>
>> ---
>>   tools/testing/selftests/proc/proc-pidns.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/testing/selftests/proc/proc-pidns.c b/tools/ 
>> testing/selftests/proc/proc-pidns.c
>> index 25b9a2933c45..6f7c10fe97b3 100644
>> --- a/tools/testing/selftests/proc/proc-pidns.c
>> +++ b/tools/testing/selftests/proc/proc-pidns.c
>> @@ -6,6 +6,7 @@
>>   #include <assert.h>
>>   #include <errno.h>
>> +#include <fcntl.h>
>>   #include <sched.h>
>>   #include <stdbool.h>
>>   #include <stdlib.h>
> 
> thanks,
> -- Shuah


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