(2.6.12) is there any reason for alarm() call to add 1 to the returned value?

[Jacky Malcles <Jacky.Malcles@bull.net>]

I've:
Linux version 2.6.12-rc6
LSB_VERSION="1.3"
Red Hat Enterprise Linux AS release 4 (Nahant)
Gnu C    gcc (GCC)     3.4.3 20041212 (Red Hat 3.4.3-9.EL4)
Gnu make               3.80
util-linux             2.12a
mount                  2.12a
modutils               3.1-pre5
e2fsprogs              1.35
pcmcia-cs              3.2.7
PPP                    2.4.2
isdn4k-utils           3.3
Linux C Library        2.3.4
Dynamic linker (ldd)   2.3.4

this behavior is new:
       alarm() does not return the number of seconds  remaining  until  any
      previously  scheduled  alarm was due to be delivered
 but
        it returns (the number of seconds  remaining + 1)
(with 2.6.10 and previous, 1 was not added to the returned value)


----------------------------------------------------------------------------------
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <signal.h>

int almreceived = 0;            /* flag to indicate SIGALRM received or not */

void setup();                   /* Main setup function of test */
void sigproc(int sig);          /* signal catching function */

int
main(int ac, char **av)
{
        int time_sec1 = 10;     /* time for which 1st alarm is set */
        int time_sec2 = 5;      /* time for which 2st alarm is set */
        int ret_val1, ret_val2; /* return values for alarm() calls */
        int ret_val3;
        int sleep_time1 = 3;    /* waiting time for the signal */
        int sleep_time2 = 6;    /* waiting time for the signal */

        /* Perform global setup for test */
        setup();

                /*
                 * Call First alarm() with non-zero time parameter
                 * 'time_sec1' to send SIGALRM to the calling process.
                 */
                ret_val1 = (alarm(time_sec1));

                /* Wait for signal SIGALARM */
                sleep(sleep_time1);

                /*
                 * Call Second alarm() with non-zero time parameter
                 * 'time_sec2' to send SIGALRM to the calling process.
                 */
                ret_val2 = (alarm(time_sec2));

                /* Wait for signal SIGALRM */
                sleep(sleep_time2);

                /*
                 * Check whether the second alarm() call returned
                 * the amount of time previously remaining in the
                 * alarm clock of the calling process, and
                 * sigproc() executed when SIGALRM received by the
                 * process, the variable almreceived is set.
                 */
                printf("ret_val2 returned = %d \n",ret_val2);
                printf("ret_val2 expected = %d\n",time_sec1 - sleep_time1);
                if ((almreceived == 1) &&
                    (ret_val2 == (time_sec1 - sleep_time1))) {

                        /*
                         *  Make sure the system cleaned up the alarm
                         *  after it delivered it.
                         */
                        ret_val3 = (alarm(0));

                        if (ret_val3 != 0) {
                                printf("System did not "
                                       "clean up delivered "
                                       "alarm");
                        } else {
                                printf("Functionality of "
                                       "alarm(%u) successful",
                                        time_sec2);
                        }
                } else {
                        printf("alarm(%u) fails, returned %d, "
                               "almreceived:%d",
                               time_sec2, ret_val2, almreceived);
                }

        return 0;
        /*NOTREACHED*/
}
/*
 * sigproc(int) - This function defines the action that has to be taken
 *                when the SIGALRM signal is caught.
 *   It also sets the variable which is used to check whether the
 *   alarm system call was successful.
 */
void
sigproc(int sig)
{
        almreceived = almreceived + 1;
}

/*
 * setup() - performs all ONE TIME setup for this test.
 *  Setup the signal handler to catch SIGALRM.
 */
void
setup()
{
        if (signal(SIGALRM, sigproc) == SIG_ERR) {
                      printf("signal() fails to catch SIGALARM, errno=%d",
                         errno);
        }
}
-----------------------------------------------------------
result:
------
ret_val2 returned = 8
ret_val2 expected = 7

I'm interested knowing what is the expected behavior ...

many thanks,



--
 Jacky Malcles    	     B1-403   Email : Jacky.Malcles@bull.net
 Bull SA, 1 rue de Provence, B.P 208, 38432 Echirolles CEDEX, FRANCE
 Tel : 04.76.29.73.14
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/