[DragonFlyBSD - Bug #3329] (In Progress) WIFSIGNALED(x) should return false when child is continued by SIGCONT

[bugtracker-admin at leaf.dragonflybsd.org]

Issue #3329 has been updated by liweitianux.

Category set to Kernel
Status changed from New to In Progress

So I've searched the @WIFSIGNALED(x)@ macro in all BSDs,
and found OpenBSD and we don't exclude the @SIGCONT@ signal,
while FreeBSD and NetBSD do.

I'll update this macro later.  Thanks.

----------------------------------------
Bug #3329: WIFSIGNALED(x) should return false when child is continued by SIGCONT
http://bugs.dragonflybsd.org/issues/3329#change-14505

* Author: JunT
* Status: In Progress
* Priority: Normal
* Category: Kernel
* Target version: 6.4
* Start date: 2022-09-20
----------------------------------------
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:

<pre>
0x117f: stopped
0x0013: signaled: 19
0x0013: continued
0x0000: exited: 0
</pre>

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

On FreeBSD it gives:

<pre>
0x117f: stopped
0x0013: continued
0x0000: exited: 0
</pre>

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

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

<pre>
<code class="C">
#define WIFSIGNALED(x)  (_WSTATUS(x) != _WSTOPPED && _WSTATUS(x) != 0 && (x) != 0x13)
</code>
</pre>

I think DragonFly should use the same definition.

Jun


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

<pre>
<code class="C">
#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;
}
</code>
</pre>



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