The general argument isn't so much about "testing" vs "macros", because #ifdef LIBRARY_VERSION is also a test of a macro's value, but what type of thing should

The general argument isn't so much about "testing" vs "macros", because #ifdef LIBRARY_VERSION is also a test of a macro's value, but what type of thing should be tested. Whether to test the functionality or the labels of it, whether to test the things that the computer runs or something that is part of a comment, whether you test the signifier or the signified. In this context, testing functionality would mean compiling a test program and observing the results. A macro or the existence of MUSL_LOCPATH would both be testing the labels and not the actual code.