[FFmpeg-devel] [PATCH] configure: improve check for POSIX ioctl

[James Almer]

On 8/29/2024 2:18 PM, Ramiro Polla wrote:
> On Thu, Aug 29, 2024 at 7:10 PM James Almer <jamrial at gmail.com> wrote:
>> On 8/29/2024 10:40 AM, Ramiro Polla wrote:
>>> Instead of relying on system #ifdefs which may or may not be correct,
>>> detect the POSIX ioctl signature at configure time.
>>> ---
>>>    configure          | 2 ++
>>>    libavdevice/v4l2.c | 2 +-
>>>    2 files changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/configure b/configure
>>> index 63f0429b02..ebbec49993 100755
>>> --- a/configure
>>> +++ b/configure
>>> @@ -2524,6 +2524,7 @@ HAVE_LIST="
>>>        opencl_videotoolbox
>>>        perl
>>>        pod2man
>>> +    posix_ioctl
>>>        texi2html
>>>        xmllint
>>>        zlib_gzip
>>> @@ -7158,6 +7159,7 @@ xmllint --version  > /dev/null 2>&1 && enable xmllint   || disable xmllint
>>>    check_headers linux/fb.h
>>>    check_headers linux/videodev2.h
>>>    test_code cc linux/videodev2.h "struct v4l2_frmsizeenum vfse; vfse.discrete.width = 0;" && enable_sanitized struct_v4l2_frmivalenum_discrete
>>> +test_code cc sys/ioctl.h "int ioctl(int, int, ...);" && enable posix_ioctl
>>
>> Is this check going to fail for the targets where ioctl_f has request as
>> an unsigned long int?
> 
> Yes. This is from config.log:
> 
> /tmp/ffconf.S7gHklXc/test.c: In function 'main':
> /tmp/ffconf.S7gHklXc/test.c:2:22: error: conflicting types for
> 'ioctl'; have 'int(int,  int, ...)'
>      2 | int main(void) { int ioctl(int, int, ...);; return 0; }
>        |                      ^~~~~
> In file included from /tmp/ffconf.S7gHklXc/test.c:1:
> /usr/include/x86_64-linux-gnu/sys/ioctl.h:42:12: note: previous
> declaration of 'ioctl' with type 'int(int,  long unsigned int, ...)'
>     42 | extern int ioctl (int __fd, unsigned long int __request, ...) __THROW;
>        |            ^~~~~

Cool. Should be ok then. Just remove the colon at the end of the check 
since test_code() will add one. Some compiler settings like -pedantic 
may complain about it, so better safe than sorry.