Xlib: extension "XFree86-DRI" missing on display "0:0"

I wrote a simple glut test code on RedHat9.0, linked good with
$gcc test.c -L/usr/X11R6/lib -lGL -lGLU -lglut -lXi -lXmu

but

$./a.out
XLib: extension"XFree86-DRI" missing on display "0:0"

please tell me what is wrong, and how to.

[zen]

The problem probably is that you haven't configured X correctly and the DRI extension is not loaded. Check your configuration, however this is done on RedHat.
Before that you might want to remove -lXi -lXmu from your command line. It shouldn't be needed and it might cause some sort of trouble.