Register pointers in gcc?

    I was looking at the disklabel(8) source today and found this in editit():

        if (pid == 0) {
                register char *ed;

                sigsetmask(omask);
                setgid(getgid());
                setuid(getuid());
                if ((ed = getenv("EDITOR")) == (char *)0)
                        ed = DEFEDITOR;
                execlp(ed, ed, tmpfil, 0);
                perror(ed);
                exit(1);
        }

    How come I can stuff anything into EDITOR and not cause disklabel to segfault? I've setenv EDITOR to 16K strings and it just complains that the argument list is too long, or that the editor does not exist. Where is it storing the contents of getenv("EDITOR")?

--
Brian Tao (BT300, taob@risc.org)
"Though this be madness, yet there is method in't"