How to change VCL code?

Question

I need (to make some quick and dirty tests) to modify the code of Variants and SysUtils.

What I need to do to \"compile\" the changes?

Answer 1

Delphi runtime DCUs are precompiled. It would be a waste of time to compile them at every build.

If the code you are trying to modify is a method of a built-in class, then a class helper may help:

http://docwiki.embarcadero.com/RADStudio/en/Class_and_Record_Helpers

So the question is which part of code do you want to modify in the runtime?