Need a guideline in porting cpp to c

Thanks for your answers.
My aim is porting cpp code to asm.
Porting to c is an intermediate step.
I want to optimize the code and make it smaller, run faster and so on.
It would be better if I can convert it directly to asm.
But It looks little bit hard (for me) because of many injected codes by cpp compiler.
I think I need to understand the code first.
That's why I'm porting it to c.
But many features of cpp are hard to port to c.
I just wonder if there are any tips or guidances for doing that.