arenalloc

A simple arena allocator in C, arenalloc started off in the Squid-lang codebase, but has become a stanalone single file library. Current version is 1.1.3.

Goal

arenalloc aims to be simple and decently fast and versatile to be used in small and medium size-sized projects. Memory safety is also an importatnt concern (it's an allocator after all), and currently no bugs or memory leaks are known (tested with example.c, UBSan and ASan).

Documentation

Documentation can be found inside arenalloc.h. The following is an excerpt from the top of the file:

/*   Arena allocator - commissions memory blocks from the OS and uses them to
 * allocate memory for the program. Freed blocks are not returned to the OS
 * until they are also decommited and can thus be reused by the arena.
 *
 *  Every allocation allocates a contiguous memory range, and thus all
 * allocations must be smaller the block size. This implementation also supports
 * variable block sizes that guarrantee 1 block/allocation (so it becomes a
 * linked list allocator). In general you should either use the variable mode,
 * or have a block size significantly larger than that of individual allocations
 * . Arena block sizes can be changed at any time by setting `arena.blk_size`.
 *
 *   In general, you can only free an entire block at a time, but this
 * implementation also supports freeing the last N allocated bytes in an arena.
 *
 *   This implementation does not rely on a specific memory allocator (such as
 * malloc), but instead, each arena has a pointer to an allocator function which
 * is used to commission blocks. That being said, I've only tested it with the
 * malloc implementations provided by Clang and GCC on x64 Linux.
 *
 *  arenalloc is modular and easily extendable if more features are desired down
 * the road. Also, have I mentioned it has a print function?!
 *
 * Macro config:
 *	 ARENALLOC_ASSERT - controls the `assert` function used (`assert` by def)
 *	 ARENALLOC_STATS - keep allocation statistics per arena (undef by default)
 *	 ARENALLOC_DEF_ARENA - declare a static arena and macro function wrappers
 * to use it wihthout havin to pass it around yourself. (undefined by default)
*/

For more informations (especially about arena stats) see the definition of arena_t and the implementation of different functions (basically just read the code - it's not that complicated).

Future features under consideration

• thread safety
• proper testing
• block data allignment options
• better support for different backends (or even a native one with syscalls)
• defragmentation system (block splitting/merging, 1 head/block)

Compiling

All you need to do in compile arenalloc.c with a compiler that supports gnu89. An example compile command can be found at the top of example.c.

Licensing

arenalloc is destributed under the MIT license. See LICENSE.