gcc -pipe -O2 -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I. -DLINUX -D_FORTIFY_SOURCE=2 -c -o lock.o lock.c
lock.c: In function 'do_lock':
lock.c:81:16: error: storage size of 'file_lock' isn't known
struct flock file_lock;
^
lock.c:83:22: error: 'F_WRLCK' undeclared (first use in this function)
file_lock.l_type = F_WRLCK;
^
lock.c:83:22: note: each undeclared identifier is reported only once for each function it appears in
lock.c:104:20: error: 'F_SETLKW' undeclared (first use in this function)
if (fcntl(f->fd, F_SETLKW, &file_lock) == 0)
^
lock.c:147:12: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result]
fgets(prompt, sizeof(prompt), stdin);
^
<builtin>: recipe for target 'lock.o' failed
make: *** [lock.o] Error 1
==> ERROR: A failure occurred in build().
Aborting...


Steps to reproduce:
sudo extra-x86_64-build