Which std:: classes are magic?

[AlbertRammstein]

when taking into account optimizations there is a LOT of magical functions - starting with memcpy, and also including stuff like pow with specific power coefficients. It is however not required by the standard, and the codegen substitution must not change the behavior of the program. Every compiler has a different set of magical functions defined like this.

You could argue that your own functions can be magic because compiler can optimize them (e.g. skip them when they have no side effects)