isgasho / rust-malloc

A pure Rust memory allocator

Rust malloc

A pure-Rust proof-of-concept implementation of malloc/free for x86-64 Linux. It is very, very basic: a linked list of allocations (traversed on every malloc call!), first-fit strategy and all allocations come directly from the brk syscall. As such, it is very slow, not-threadsafe and generally bad. There is little-to-no error checking.

Uses a modified version of zero.rs and a tiny syscall wrapper. Requires a recent rustc from master.

There is an example of a custom version of ~T using this allocator at the bottom of malloc.rs.

Test with:

make
./malloc

To enable the debugging asserts:

make debug
./malloc-debug

Code map:

• malloc.rs contains malloc, free, etc, as well as main and some tests/examples.
• types.rs contains the allocation header (Header, surprisingly) as well some newtype structs around raw pointers (Box and Data; in theory these have no runtime cost over using *mut Header and *mut u8 directly) which make the implementation relatively type-safe.
• util.rs & diag.rs contain utilities and tools for printing diagnostics about the current allocation state.

Only useful for segfaulting and generally making programs incorrect.

TODO

• Use mmap.
• Return memory to the OS.
• Merge adjacent free cells better.

Wishlist

• Make it fast.
• Support other platforms/operating systems.