C for high level programmers (slides)

If you want arrays of variables, you need pointers. It's not enough to know the value of an int (the first element of the array), but you need the pointer to an int (pointer to the first element of the array). Now you can increment the pointer to go to the next element. You couldn't do this with a simple value.

Also, suppose you want to pass a variable of a large data type, like an image, to a function. Instead of copying the entire variable, just pass the cheap pointer. The analogy is giving someone an URL vs the source code of the site for them to paste in the browser (You can't fit the latter onto a QR code, for instance, but you can the former).

This comes from a restriction of almost all existing computer architectures. You have a small amount (16 on amd64) of 'variables' called registers that you can directly work with. Additional variables have to be loaded from and stored in memory, which is slower and requires you to know that variables address (pointer) -- which is just an integer with special meaning. In C, variables you never take a pointer to might live exclusively in a register, and all local variables are stored at a fixed offset to a special 'stack pointer' which is kept in a dedicated register.

Some architectures try to have a more sophisticated approach and have some sort of 'fat pointer' in which pointer values have a special tag and are subject to special rules so they can only point to valid objects. The exact rules used and what constitutes 'valid' is specific to the architecture. Intel has introduced mpx on newer processors to check array bounds with such a scheme, and older processors such as LISP machines have much stronger (but less efficient) schemes.

If you don't have a copy of the value, you need someway to find it, right? That's a pointer, or a reference, or a handle. (These are all approximate synonyms for some way to "address" the data.) In the olden days, there was a fixed mapping from a number to a physical location in storage, but now there are many levels of indirection, such as virtual memory, pools, etc.

I think the problem with learning C is that you need to learn stuff like make, autoconf, how the compiler + preprocessors work (what do all those flags even mean!?), how making "cross-platform" stuff works, how to pull in and use "libraries", C-isms, how to test, etc. C itself is a very small and simple language, but the tooling and patterns are old and mysterious.

In college I learned how to program embedded systems with C (and ASM). Once I knew how to debug, build, and push it onto the device, it was surprisingly easy and beautiful. There's no confusing and magical abstractions, it's just you and the hardware. You pull up the microcontroller's manual, and as long as you have an idea of what the lingo means, you can make it dance to your will.

Something I disliked was that with both microcontrollers I used, there was dark magic involved in building and uploading your binary. One of the devices provided examples for a specific IDE, so I imported that example and used it as a base. I could keep modifying it and keep adding files, but I never managed to setup a "new" project. The other device was similar, but instead of using an IDE it provided a Makefile, which was nicer.

Does anyone know any good resources on learning and writing real-world C? I've looked at C projects here and there over the years, with the most interesting being GNU Coreutils... But even if I can eventually understand what some code does, how do I learn why it does it that way?

I'd love for a guide that showed things like: "do X and Y because of this and that", "test X and Y by running the following", "write tests using XYZ", "debug X using Tool A, and Y using Tool B", "pull in this library by copying these files into these places, and use it by adding the following lines to the following files", "generate docs by pulling in this tool and set it up by doing the following", etc.

In the web world there's a massive set of problems, but it tends to be easy to find "boilerplate" generators that will get you up and running. And after you've tried out a few of them, you can usually pick up how people are mixing and matching different tools.

EDIT: Another comment linked to "Learn C The Hard Way" [0], and after browsing through the chapters it seems to cover a lot of the topics I'm interested in.

[0] http://c.learncodethehardway.org/book/

I just wrote a comment [0] about my problems with learning C, would you say this book covers the issues that I raised and is worth reading?

EDIT: Well, I just looked over the chapters in this book and I'm now extremely excited to give it a read. It seems to cover most of the topics that I'm interested in, so thank you SO MUCH for sharing!

[0] https://news.ycombinator.com/item?id=9636122