[hackers] [scroll] fix race condition between sigwinch and sigchld || Jan Klemkow

[git]

commit 1dbf2dce08892df710645ddbd2ce12759ec95078
Author:     Jan Klemkow <j.klem...@wemelug.de>
AuthorDate: Thu Apr 30 22:12:50 2020 +0200
Commit:     Jan Klemkow <j.klem...@wemelug.de>
CommitDate: Thu Apr 30 22:12:50 2020 +0200

    fix race condition between sigwinch and sigchld
    
    sigwinch died if it tries to set the window size
    to a file descriptor of an exited child.  Thus,
    we just ignore this error in that situation.

diff --git a/scroll.c b/scroll.c
index 9242936..28cd653 100644
--- a/scroll.c
+++ b/scroll.c
@@ -96,8 +96,11 @@ sigwinch(int sig)
 
        if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1)
                die("ioctl:");
-       if (ioctl(mfd, TIOCSWINSZ, &ws) == -1)
+       if (ioctl(mfd, TIOCSWINSZ, &ws) == -1) {
+               if (errno == EBADF)     /* child already exited */
+                       return;
                die("ioctl:");
+       }
        kill(-child, SIGWINCH);
        doredraw = true;
 }