Need a guideline in porting cpp to c

How are you doing?
I'm trying to port cpp code to c. It's not a huge code.
But I'm kind of an old style guy so I feel dizzy. I'm studying cpp syntax again cause I forgot it almost.
Anyway, is there any guidance fot this subject? If so please let me know.
I googled the net but with no succeed.
By the way I found Comeau C/C++ compiler can convert cpp source to c.
Does anybody have tried it before? Is it reliable?
Thanks for reading.