readline on MacOS X

gistfile1.txt

OS X does not come with readline, rather, it comes with libedit which is touted as being a readline-compatible replacement.
This may be true for basic usage, but advanced usage will run into compabitily problems.

For example, trying to build https://github.com/ulfalizer/readline-and-ncurses on Mac will complain about not finding some variables exported by readline.

Solution: brew install readline

Brew will not override OS X's readline (which is really libedit). Its output helpfully states:

--------------------
readline is keg-only, which means it was not symlinked into /opt/homebrew,
because macOS provides BSD libedit.

For compilers to find readline you may need to set:
  export LDFLAGS="-L/opt/homebrew/opt/readline/lib"
  export CPPFLAGS="-I/opt/homebrew/opt/readline/include"
--------------------

Adding the above compile and linker flags into the Makefile solved the problem.