What happens to parent process, when a child process is created using vfork() and killed before calling exec

Question

When a process is created using vfork() child process is created and starts running in the parent process address space, until exit() or exec() is called.

What happens to the parent process, if some one kills the child process before calling the exit()/exec()?

Comments

This is what Wiki is saying -
The use of vfork for any purpose except as a prelude to an immediate call to a function from the exec family (and a select few other operations) gives rise to undefined behavior. In particular the Linux man page for vfork strongly discourages its use:

It is rather unfortunate that Linux revived this specter from the past. The BSD man page states: "This system call will be eliminated when proper system sharing mechanisms are implemented. Users should not depend on the memory sharing semantics of vfork() as it will, in that case, be made synonymous to fork."


So behavior may be undefined, waiting for others to comment.

Answer 1

According to the vfork man page:

vfork() differs from fork(2) in that the calling thread is suspended until the child terminates (either normally, by calling _exit(2), or abnormally, after delivery of a fatal signal), or it makes a call to execve(2). Until that point, the child shares all memory with its parent, including the stack. The child must not return from the current function or call exit(3), but may call _exit(2).

So I should imagine that when the child is killed, the parent resumes, and can call wait() and retrieve the child's exit status.

Answer 2

When a process is created using vfork() child process is created and starts running in the parent process address space, until exit() or exec() is called.

Wrong. The child runs in its own address space.

What happens to the parent process, if some one kills the child process before calling the exit()/exec()?

"Killing" a process means sending it a signal. If there is no signal handler (or the signal cannot be caught) the kernel phase of the process wraps up and informs the parent via a SIGCHLD signal. If the parent is dead, it informs process 1 (traditionally init, now systemd).
See signal(2) and _exit(2).

Comments

My apologies. I misread your question and described what happens with fork() rather than vfork().