This is a modern refactoring of the simple "storage allocator" found in the classic K&R TCPL book.
It retains the simplicity and efficiency of the original, adding a few improvements :
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Localised, encapsulated state :
The K&R allocator uses a global freelist, so there is one global allocator. Instead, we load/store the freelist and other state in
struct allocators, so there may be any number of independent, scope-bound allocator objects. -
Custom memory pools :
Where the original obtains memory from the OS through a syscall, here the user adds memory region(s) to an allocator object via
allocator_add(). -
Safe, correct & portable :
This allocator is thread-safe using lightweight syncronisation techniques - spinlocks composed of C11 atomics.
It also checks for integer overflow and treats this as an allocation error and handles alignment in a machine-independant way. In fact, the library is virtually freestanding.
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Queryable :
Like most modern allocators, this one too can query the real size of an allocation, with
allocator_allocsz(). It also allows for querying each block's size in the freelist usingallocator_for_blocks(). The K&R allocator is, in contrast, entirely opaque.