[CentOS] How get a spec preprocesed with all macros expanded.

Hi,

I need to get a spec file with all macro exanded, so i can extract info 
of some tags, that my be consitional based on macros, i know that some 
rpm utils need to make this to figure out dependencies and so on.

I don't know if is posible to get a preprocesed spec file with actual 
Centos & rpm tools, if this is on librpm, i can make a simple tool to 
make this.

Regards.