@elextr following your suggestion, it is working now. As you mentioned, GDB doesn't find the files, even after they are added to the search path with `dir`, until after the program starts running. But they're available after `(gdb) start` so that's fine.
Seems like this should be added to the documentation. Maybe something like
Because most of Geany is a library, in order to use GDB, you'll need to install the version of Geany you want to debug. You can install to a different directory in order to not overwrite an existing install with `./configure --prefix <a directory>`. You'll also need to tell GDB about where the source files are with GDB's `dir` command. Most source files won't be loaded until after Geany starts running, but you can run `(gdb) start` to break at the start of main and set breakpoints etc. from there.
in the GDB section of HACKING?