I am a scientist who has semi-frequently written code in C (and other compiled languages like Fortran). When it comes time to compile, I typically tape together a Makefile from past projects and hope for the best, but even then I spend more time than I'd like to admit trying to figure out why my project is not being compiled or linked correctly. I've had a hard time finding any resources that aren't extremely surface level, or else are not behind some type of paywall. Can anyone recommend me some reading so that I can confidently write Makefiles and compile programs and actually understand what the different flags and commands are doing? I don't need extreme "under the hood" information as I don't intend to do things like write my own compiler, I just want to understand the process a little better. Help a scientist out!

I've recently built a brainfuck just-in-time compiler and I'm looking for my next project. I think compiling a more complicated (and more easily written) language would build on what I've learned so far. Rather than design my own language from the ground up, I'd prefer to work with a toy language that already has existing programs and a spec. This would both save me some work and give me more solid ground to build upon.