Allocating on the Stack

This post explains Go's compiler improvements for stack-based slice allocations to reduce heap pressure and garbage collection overhead.

• •Stack allocations are cheaper than heap allocations and produce no GC load, as they are reclaimed with the stack frame itself
• •In Go 1.24, only constant-sized slice backing stores (e.g., make([]task, 0, 10)) could be stack-allocated when they don't escape to the heap
• •Go 1.25 adds automatic small (32-byte) stack-allocated backing stores for variable-sized make calls, enabling zero heap allocations when the requested size fits
• •Go 1.26 extends this to append-allocated slices, using a stack buffer as the initial backing store before falling back to heap doubling
• •For escaping slices, Go 1.26 automatically applies a move2heap transformation, performing exactly one right-sized heap allocation only when needed at return