What is the best way to get a 64bit c++11 capable compiler?

Hello,

I recently got an Ultra 45 to test my code better and have already
been able to fix a couple things thanks to the ease of getting a
modern OS working quickly.

Unfortunately though I am having some trouble with some of my
c++ code.  Compilers are crashing when they need more than
4 GB RAM. I have tried gcc-8.3.0p4 and clang 8.0.1 but neither
work. Are these packages 32 bit ?!  What is the best way for me to
get a working 64 bit c++11 compiler?

I'm running OpenBSD 6.6 but am open to upgrading. If there are
no 64 bit packages for what I need any tips for compiling a 64 bit
compiler from a 32 bit compiler would be great.

Thanks,
Eric