[U-Boot] run_command() / do_run() fails in standalone application

Hi,

i'm using the standalone application to run the command's using do_run() / run_command function available in /common/mani.c. i followed the steps mentioned in README.standalone file. there is no compilation error or warnings. when i tftp that application to 0x40000 to Power PC evaluation board then i start executing go 40004 command its not doing any thing. i suppose to the get help command info after executing this application. why its not running that command? code is as follows

char *p = getenv ("help") run_command (p, 0); do_run(NULL,0,1,"help");

Thanks Rudresh