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/* Test of flock() function.
Copyright (C) 2008-2023 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include <sys/file.h>
#include "signature.h"
SIGNATURE_CHECK (flock, int, (int, int));
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include "macros.h"
static void
test_shared (const char *file, int fd)
{
/* Should be able to acquire several shared locks on a file, through
* different file table entries.
*/
int fd2, r;
ASSERT (flock (fd, LOCK_SH) == 0);
fd2 = open (file, O_RDWR, 0644);
ASSERT (fd2 >= 0);
r = flock (fd2, LOCK_SH | LOCK_NB);
ASSERT (r == 0); /* Was able to acquire a second shared lock. */
ASSERT (flock (fd, LOCK_UN) == 0);
ASSERT (close (fd2) == 0);
}
static void
test_exclusive (const char *file, int fd)
{
/* Should not be able to acquire more than one exclusive lock on a file. */
int fd2, r;
ASSERT (flock (fd, LOCK_EX) == 0);
fd2 = open (file, O_RDWR, 0644);
ASSERT (fd2 >= 0);
r = flock (fd2, LOCK_EX | LOCK_NB);
ASSERT (r == -1); /* Was unable to acquire a second exclusive lock. */
#if 0
/* The Linux manual page of flock(2) says:
"A process may only hold one type of lock (shared or exclusive) on a
file. Subsequent flock() calls on an already locked file will convert
an existing lock to the new lock mode."
So, the call below should convert the exclusive lock for fd to a shared
and thus succeeds. The fact that it doesn't but instead fails is
apparently a bug. */
/* The Solaris manual page of flock(2) says:
"More than one process may hold a shared lock for a file at any given
time, but multiple exclusive, or both shared and exclusive, locks may
not exist simultaneously on a file. ...
Requesting a lock on an object that is already locked normally causes
the caller to block until the lock may be acquired. If LOCK_NB is
included in operation, then this will not happen; instead, the call
will fail and the error EWOULDBLOCK will be returned."
So, the call below should fail and set errno to EWOULDBLOCK. The fact
that it succeeds is apparently a bug. */
r = flock (fd2, LOCK_SH | LOCK_NB);
ASSERT (r == -1);
#endif
ASSERT (flock (fd, LOCK_UN) == 0);
ASSERT (close (fd2) == 0);
}
int
main (int argc, char *argv[])
{
int fd;
const char *file = "test-flock.txt";
/* Open a non-empty file for testing. */
fd = open (file, O_RDWR | O_CREAT | O_TRUNC, 0644);
ASSERT (fd >= 0);
ASSERT (write (fd, "hello", 5) == 5);
#if defined __linux__ || defined __ANDROID__
/* Invalid operation codes are rejected by the Linux implementation and by
the gnulib replacement, but not by the Mac OS X implementation. */
ASSERT (flock (fd, LOCK_SH | LOCK_EX) == -1);
ASSERT (errno == EINVAL);
ASSERT (flock (fd, LOCK_SH | LOCK_UN) == -1);
ASSERT (errno == EINVAL);
ASSERT (flock (fd, LOCK_EX | LOCK_UN) == -1);
ASSERT (errno == EINVAL);
ASSERT (flock (fd, 0) == -1);
ASSERT (errno == EINVAL);
#endif
test_shared (file, fd);
test_exclusive (file, fd);
/* Close and remove the test file. */
ASSERT (close (fd) == 0);
ASSERT (unlink (file) == 0);
return 0;
}
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