Another problem though, project dependencies...

I built and ran and debugged Audacity. I made a change in add.c in libnyquist/nyqsrc. I built the solution. The libnyquist project recompiled, but apparently it was not linked. When I try to put a breakpoint in add.c, it’s disabled because my source is supposedly newer than the build. I changed the debugging options to allow that, and verified by examining variables that my change was not effective in my build.

What am I doing wrong? I don’t want to rebuild the whole project to guarantee that my change is linked!

RIght click on the Audacity project, Project Only, Link Only Audacity – seems to fix it, but I thought just rebuilding the solution should have done that.

I can’t be sure but you may have had the Nyquist project selected in the Solution Explorer thus when you clicked on build solution you may have only been building Nyquist. Then when you right-click on the Audacity Project it became the selected/current project and its solution contains all the other projects except maybe Help and Locale.