setup_environment: code shrink

run_shell: mark as NORETURN
setup_environment, run_shell: add usage comments
login: add FIXME :(

function                                             old     new   delta
UNSPEC_print                                          64      66      +2
sulogin_main                                         509     506      -3
mkfs_minix_main                                     3070    3067      -3
login_main                                          1615    1612      -3
su_main                                              461     448     -13
setup_environment                                    261     206     -55
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/5 up/down: 2/-77)             Total: -75 bytes
   text    data     bss     dec     hex filename
 772578    1051   10724  784353   bf7e1 busybox_old
 772502    1051   10724  784277   bf795 busybox_unstripped

1 files changed, 12 insertions, 13 deletions

diff --git a/libbb/setup_environment.c b/libbb/setup_environment.c
index a6f44f7f0..19a2c6db5 100644
--- a/libbb/setup_environment.c
+++ b/libbb/setup_environment.c
@@ -36,36 +36,35 @@ void setup_environment(const char *shell, int loginshell, int changeenv, const s
                 const char *term;
 
                 /* Change the current working directory to be the home directory
-                 * of the user.  It is a fatal error for this process to be unable
-                 * to change to that directory.  There is no "default" home
-                 * directory.
-                 * Some systems default to HOME=/
-                 */
+                 * of the user */
                 if (chdir(pw->pw_dir)) {
                         xchdir("/");
                         fputs("warning: cannot change to home directory\n", stderr);
                 }
 
-                /* Leave TERM unchanged.  Set HOME, SHELL, USER, LOGNAME, PATH.
+                /* Leave TERM unchanged. Set HOME, SHELL, USER, LOGNAME, PATH.
                    Unset all other environment variables.  */
                 term = getenv("TERM");
                 clearenv();
                 if (term)
                         xsetenv("TERM", term);
-                xsetenv("HOME",    pw->pw_dir);
-                xsetenv("SHELL",   shell);
-                xsetenv("USER",    pw->pw_name);
-                xsetenv("LOGNAME", pw->pw_name);
-                xsetenv("PATH",   (pw->pw_uid ? bb_default_path : bb_default_root_path));
+                xsetenv("PATH", (pw->pw_uid ? bb_default_path : bb_default_root_path));
+                goto shortcut;
+                // No, gcc (4.2.1) is not clever enougn to do it itself.
+                //xsetenv("USER",    pw->pw_name);
+                //xsetenv("LOGNAME", pw->pw_name);
+                //xsetenv("HOME",    pw->pw_dir);
+                //xsetenv("SHELL",   shell);
         }
         else if (changeenv) {
                 /* Set HOME, SHELL, and if not becoming a super-user,
                    USER and LOGNAME.  */
-                xsetenv("HOME",  pw->pw_dir);
-                xsetenv("SHELL", shell);
                 if (pw->pw_uid) {
+ shortcut:
                         xsetenv("USER",    pw->pw_name);
                         xsetenv("LOGNAME", pw->pw_name);
                 }
+                xsetenv("HOME",    pw->pw_dir);
+                xsetenv("SHELL",   shell);
         }
 }