Lex, thank you for your helpful reply. I did find that my distro also has a geany-devel package which I downloaded. I then deleted the source code for geany and geany-plugins I had downloaded from github and subsequently built the helloworld.c example without any problems.

All good, now my plan is to take the classbuilder.c source code, rename it to symfony.c and tweak this code to do what I would like it to do. I quickly tried to run the same gcc command I used for helloworld.c for this symfony.c (renamed from classbuilder.c) but it failed to compile. The first error referred to PACKAGE_VERSION being undefined. It is probably defined in some other header file that I will search for later.