C is my favorite language, but I have never worked with it professionally. I've completed "Learn C the Hard Way".
What's another challenging text for a professional developer who is a C dilettante?
I've got a few on my shelf I enjoy in that category:
Game Programming Patterns by Robert Nystrom discusses many patterns, including a number related to dynamic allocation and memory management, from a game development perspective. (Written mainly for C++, although you could take on the challenge of implementing the patterns in C!) Besides that, his comical, bantering style makes for a really fun read.
Hacker's Delight by Henry S. Warren contains a number of mind-bending algorithms that operate in C and Assembly.
Game Engine Architecture by Jason Gregory explores the myriad of challenges that game engine developers face, especially issues of performance and memory management. Again, this written primary for C++, but you can approach many of the problems from a C perspective as well.
The Art of Computer Programming by Donald Knuth. Okay, I don't own this one, but I really really want a copy! It's quite a challenge to wrap your head around his algorithms and patterns, many of which are fundamental to the field of computer science.
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