Multithreading is an extremely advanced topic. Make sure you first understand how STL template library works, how debugging applies to Debug & Release modes.

Also look for naming conventions. CamelCase is commonly used for functions (and sometimes variables, sometimes theyStartWithLowerCase but still camel case) and ALL_CAPS for macro definitions.

But mixing CamelCase with CamelCase_undercored_spaces is very weird and will confuse/annoy most coworkers you will encounter throughout your life.

Because you rebuilt everything. Meaning you updated object files that may not have been properly updated when they should have been.

Now every object file is “on the same page”.

L. Spiro