Some common C language function for atmega32

I have a problem with c language function of float numbers to string conversion.
I have used sprintf, vfprintf. In atmega32, I am converting a float number into string so that I may print it in LCD. These commands compiles with out error but converts only ' ? '.
plz help me out. :-s

attach ur code and circuit and we can work out the problem.

Now the problem is solved.
There was some setting in makefile of project.
I had to include some wordings in linking properties.
Thanks
:-)