11.8

--- tiny.origin.c	2021-02-25 07:26:33.302592754 +0000
+++ tiny.8.c	2021-02-25 07:26:33.302592754 +0000
@@ -12,6 +12,7 @@
 void serve_dynamic(int fd, char *filename, char *cgiargs);
 void clienterror(int fd, char *cause, char *errnum,
     char *shortmsg, char *longmsg);
+void sigchild_handler(int sig);
 
 int main(int argc, char **argv)
 {
@@ -26,6 +27,9 @@
     exit(1);
   }
 
+  if (Signal(SIGCHLD, sigchild_handler) == SIG_ERR)
+    unix_error("signal child handler error");
+
   listenfd = Open_listenfd(argv[1]);
   while (1) {
     clientlen = sizeof(clientaddr);
@@ -38,6 +42,15 @@
   }
 }
 
+void sigchild_handler(int sig) {
+  int old_errno = errno;
+  int status;
+  pid_t pid;
+  while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
+  }
+  errno = old_errno;
+}
+
 /*
  * doit - handle one HTTP request/response transaction
  */
@@ -196,7 +209,6 @@
     Dup2(fd, STDOUT_FILENO);         /* Redirect stdout to client */ //line:netp:servedynamic:dup2
     Execve(filename, emptylist, environ); /* Run CGI program */ //line:netp:servedynamic:execve
   }
-  Wait(NULL); /* Parent waits for and reaps child */ //line:netp:servedynamic:wait
 }
 
 /*