C++ set stack pointer

In my C++ / C project I want to set the stack pointer equal to the base pointer... Intuitively I would use something like this:

asm volatile(
    "movl %%ebp %%esp"
);

However, when I execute this, I get this error message:

Error: bad register name `%%ebp %%esp'

I use gcc / g++ version 4.9.1 compiler.

I dont know whether I need to set specific g++ or gcc flag though... There should be a way to manipulate the esp and ebp registers but I just don't know the right way to do it.

Doe anybody know how to manipulate these two registers in c++? Maybe I should do it with hexed OP codes?