sizeof in preprocessor command doesn't compile with error C1017

Question

I want to use preprocessor command to control code executive path. Because in this way can save runtime time.

#if (sizeof(T)==1 doesn\'t comple with error:

Answer 1

As @some-programmer-dude mentioned in the comment, sizeof is not part of the preprocessor.

you should use if constexpr if you want it to work in compile time.

if you don't care if it happens in compile time or run-time just use a regular if statment

keep in mind that if constexpr is a new feature in C++17!