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ccgargantua / repository
Super small, simple, and (almost) completely C89-compliant single-header arena "allocator".
Single-header arena allocator. C89 Compatible (in most cases).
arena.hArena allocators are a simple way to achieve easier, faster, and safer dynamic memory management by allowing multiple allocations to be freed as a group. This is done by allocating memory in large regions and then distributing portions of that memory as needed, reducing the amount of malloc calls (which are slow compared to simple pointer arithmetic).
When you destroy the arena you also free it and all of its contents, reducing the amount of free calls which are also slow. Going further, you can clear arenas by simply resetting their memory pointers to 0, allowing you to reuse them and eliminating the need for even more malloc's and free's.
You can learn more about arena/zone/region allocators by reading this fantastic article.
I'll keep this short. This is not completely C89 compliant due to representing pointers as integers, something that cannot be done if strictly following C89 due to lack of uintptr_t I am maintaining C89 compliance for fun, not because I use it. I personally am a C11 enjoyer. If you think C89 is the only way, well, good for you! But you're wrong.
Whenever I share this project with other programmers, one of the most common responses I receive is something along the lines of: You should NEVER put implementation/logic code in a header file! I take issue with this statement for three reasons...
It shows that an outdated and, by consequence, harmful construct is still being enforced in the education system, which is where said construct is usually introduced.
Very rarely does the person making this statement have an actual reason for believing it. Does this person ever think about why they should "NEVER put implementation/logic code in a header file"? Simply regurgitating what they've heard without any basis for why they chose to agree with it does not help me in any way, and this person should not expect me to just accept it as they have done.
The largest and most valid criticism of header-only/single-header libraries is that a change to the header requires re-compilation of all files that include it. In the case of my project, making changes to arena.h, even though the actual implementation is only contained in the translation unit that #define's the ARENA_IMPLEMENTATION macro, will result in the rebuild of all files that include it. The solution? Once arena.h is in the desired state, stop making changes!
Linking is sluggish and complicated. Many beginners often times struggle with learning the linking process, and they are also the biggest culprit when it comes to writing unsafe code. This alone is enough reason for me to make this arena allocator a header-only library. My code (in its current state) is very small, roughly 300 lines. Why would I make you build and link such a small implementation when you could simply #include it once and start using it out of the box? If you really have a problem with it, this allocator in the single-header format does not prevent you from following the source+header construct if you so desire. Heck, feel free to fork it and make it source+header, it's open source for a reason!
This does not implement a kernel-level allocator, but instead wraps malloc and free (standard library or custom, your choice).
While I do believe software should be open source, I don't believe it would ethical to require software that uses this library to also be open source. In the modern age of technology and the current state of the world, writing memory-safe code is more important than ever. For this reason, this software is licensed under the Apache License Version 2.0. You are strongly encouraged to read the LICENSE (included below, in arena.h, and its own file in this repo) if you are considering using the software, unless you believe you are 100% familiar with the terms and conditions.
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