Versus the garbage collector

The big discussion about the garbage collector repeatedly comes up. This page tries to provide a summary.

Why GC is bad

• Unpredictable pauses which stop the world
• Current implementation sucks

Why GC is good

• Safe by default and non-leaking memory management
• Acceptable performance for many cases
• Supports immutable types

Common Ground

• We want something, which is safe by default

Proposals

Compiler-supported Reference Counting

Compiler generates reference counting for all references

• Pro: More predictable
• Pro: No manual rewriting necessary
• Contra: Cycles would leak
• Contra: Overhead due to inc/dec operations
• Open question: Does ARC guarantee memory safety?

Library Reference Counting

Use std.typecons.RefCounted

• Pro: Garbage collector still provides safety
• Contra: Lots of manual work
• Contra: Overhead due to inc/dec operations

DIP18: nogc attribute

• Pro: Compile-time checked
• Pro: Selective usage
• Contra: Attribute creep

Implement Certain Interface

• Cannot find original thread

External links

• The "no gc" crowd
• draft proposal for ref counting in D
• (About the Boehm GC, but generally interesting)
• The Space Cost of Lazy Reference Counting (technical report)
• Jon Harrop's answer to: Computer Programming: How do reference counting and garbage collection compare?