Why is the C++ program killed by OS

Inside the Hurd FAQ you can find some information about this case:

?? What is the login shell?

{MB} The Hurd has the concept of a not-logged in user. This user has neither user ids nor groups ids. This stems from the fact that the Hurd supports uid and gid sets and one possibility is, of course, the empty set. Rather than deny access in this case, filesystems in the Hurd offer a fourth permission triplet (i.e. rwx) which is used to determine the privileges for users with no credentials. This, however, needs to be enabled on a file by file basis. By default, the `other' permission triplet is used.

The Hurd login shell is a shell running with neither uids nor gids. To restrict access to your files, either enable and change the fourth permission triplet or change the login shell of the 'login' user in the password file to '/bin/loginpr' which implements the standard login prompt.

And remember, Hurd is not UNIX. Its a replacement for the UNIX kernel, using the Match Microkernel, so, many of the concepts from UNIX are not applicable to Hurd.

Mach is a micro-kernel, written at Carnegie Mellon University. A more descriptive term might be a greatest-common-factor kernel, since it provides facilities common to all ``real'' operating systems, such as memory management, inter-process communication, processes, and a bunch of other stuff. Unfortunately, the system calls used to access these facilities are only vaguely related to the familiar and cherished Unix system calls. There are no "fork", "wait", or "sleep" system-calls, no SIGHUPs, nothing like that. All this makes it rather difficult to, say, port GNU Emacs to a Mach box.

References:

• GNU Hurd FAQ inlined
• GNU Hurd Documentation - Authentication