Hung parent while reading stderr from child process through pipe in C++ - c++

Question

I fork a child process which in turn spawns a grand-child process and returns. If there are any errors in spawning that grand-child, the child writes to stderr using fprintf statements and exits.
I am trying to read stderr from the child process in the parent. But, the parent gets hung in the while loop reading from child process. When I look at ps -ef the child is <defunct>.
Following is the code I wrote to accomplish this. I am new to this and the search on web does not give enough information about why the parent is hung when the child is
int pipe_out[2];
// Create the pipe
if (pipe(pipe_out) < 0) {
perror("Failed pipe");
exit(1);
}
// Create the child process
int status;
pid_t pid = fork();
switch(pid) {
case -1:
perror("Failed fork");
exit(1);
case 0: { // Child
close(pipe_out[0]); // close read end
// Make stderr go to pipe write end
dup2(pipe_out[1], STDERR_FILENO);
close(pipe_out[1]);
// start my process
execvp(inp_args[0], inp_args);
_exit(EXIT_FAILURE);
break;
}
default: { // Parent
close(pipe_out[1]); // close write end
// read from child
while( read(pipe_out[0], buffer, sizeof(buffer)) )
log(stdout, "%s\n",buffer);
}
// wait for end then close other end of pipe
waitpid(pid, &status, 0);
if (WIFSIGNALED(status))
log(stdout, "killed by signal %d\n", WTERMSIG(status));
close(pipe_out[0]);
}
}