Re: Program crashes on stable/13 (but not on 12.3)

06.03.2022 2:26, Peter wrote:

Adding kib@ to CC: in case this is connected to recent commit by him.

> Hija,
> 
>  this program crashes SEGV on stable/13 after 135962 iterations,
> but continues to run on 12.3.
> 
> My stable/13 is still at 22ba2970766 - if You happen to be on a
> newer level, then please just try this out.
> 
> ------------------------------------------------------
> #include <unistd.h>
> #include <fcntl.h>
> #include <stdio.h>
> 
> main() {
>     char buf[] = "12345678901234567890123456789012345678901234567890";
>     int fd = open("/dev/null", O_RDONLY);
>     int i = 0;
> 
>     close(1);
>     dup2(fd, 1);
>     close(fd);
> 
>     while(1) {
>       fputs(buf, stdout);
>       fflush(stdout);
>       i++;
>       fprintf(stderr, "%d\n", i);
>     }
> }
> ------------------------------------------------------
> 
> I know that the code is bogus, but this is exactly what one of our
> ports does (and why it started to crash after upgrading to stable/13).
> 
> And I think it should not SEGV, anyway.
> 
> For the full story, read here:
> 
> https://forums.freebsd.org/threads/random-program-crashes-no-coredumps-and-error-94.84285/

fflush() in our libc recently got some change due to very old PR
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=76398

That change was merged to stable/13 after 13.0-RELEASE:
https://cgit.freebsd.org/src/commit/?id=afa9a1f5ec9974793a8744c55036ef5c4d08903d

I wonder if it could be connected to the problem in question,
so adding kib@ to CC: (I am sorry, Konstantin).