manmem.md 1.4KB
Summarise Contribution & Motivation
- There are lots of safe programming languages
- People don't use them
- Garbage collection is the source of inefficiency in unsafe languages
- Safe manual memory management is a potential solution to this.
- Simply add a delete operator to free memory, and an exception if that memory is then dereferenced
Methodology
- Programming model changes
- Replace GC heap with manually managed heap allocated from new keyword
- New delete operator
- Guarantee memory safety with new exception
- Does not impact on the compiler or programmer too much, no restriction on aliasing
- Delete semantics are intentionally weak for performance reasons, but maintain safety from use-after-free bugs
- Uses 64 bit hardware to assign each object new virtual addresses without reusing one until safe to do so
- The processors MMU will then detect violations as objects are unmapped from the applications address space
- Other operations allocate objects on new virtual pages as virtual operations are only allowed on pages
- Included an allocator in .NET toolchain
Critical Assessment
- Good solution that builds on other works shortcomings
- Still places burden on programmer unlikely to make changes
- Using hardware to detect violations is good idea to keep overhead low
- Somewhat non-deterministic, but this doesn't matter as the original program also was and they address this(extensive testing + debug option)