[build2] How to detect and configure #define macros?

[Boris Kolpackov]

Joshua Olson <0joshua.olson1 at gmail.com> writes:

> That sounds like a good way to do it. Or simply a list of macro definitions
> the compiler detects and where they were detected.

Now I am completely lost: "list of macro definitions the compiler detects
and where they were detected" -- what does this even mean? I've never heard
of compilers (I presume C++ compilers) detecting macros.

Boris