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Bug #3329

open

WIFSIGNALED(x) should return false when child is continued by SIGCONT

Added by JunT 3 months ago. Updated 3 months ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
-
Target version:
Start date:
09/20/2022
Due date:
% Done:

0%

Estimated time:

Description

The macro WIFSIGNALED(status) gives true even when the child process is
continued by a signal SIGCONT. I think it should be true ONLY IF the
child is terminated by a signal, as described in wait(2) man page.

On DragonFly 6.2, an example C program (see the end of this post) gives:

0x117f: stopped
0x0013: signaled: 19
0x0013: continued
0x0000: exited: 0

The two lines with status=0x0013 shows that both WIFSIGNALED(status) and
WIFCONTINUED(status) are true for this status.

On FreeBSD it gives:

0x117f: stopped
0x0013: continued
0x0000: exited: 0

The line 'signaled' is not output also on Linux and macOS.

On FreeBSD the macro is defined (in sys/wait.h) as follows:

#define WIFSIGNALED(x)  (_WSTATUS(x) != _WSTOPPED && _WSTATUS(x) != 0 && (x) != 0x13)

I think DragonFly should use the same definition.

Jun

/*==== an example C program ======*/

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>

pid_t child;
int done = 0;

void handler(int sig)
{
int status;
while(waitpid(child, &status, WNOHANG|WUNTRACED|WCONTINUED) == child) {
if (WIFEXITED(status)) {
printf("0x%04x: exited: %d\n", status, WEXITSTATUS(status));
done = 1;
}
if (WIFSIGNALED(status))
printf("0x%04x: signaled: %d\n", status, WTERMSIG(status));
if (WIFCONTINUED(status))
printf("0x%04x: continued\n", status);
if (WIFSTOPPED(status))
printf("0x%04x: stopped\n", status);
}
}

int main(void)
{
signal(SIGCHLD, handler);

if ((child = fork()) > 0) {
kill(child, SIGSTOP);
sleep(1);
kill(child, SIGCONT);
/* explicitly call handler() since we will not receive SIGCHLD */
handler(SIGCHLD);
while(!done) {
sleep(1);   /* wait for child to exit */
}
}
else { /* child */
sleep(1);
}
return 0;
}

Actions #1

Updated by tuxillo 3 months ago

  • Description updated (diff)
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