How Escape Analysis Works in Go

Escape analysis in Go determines at compile time whether a variable must be allocated on the heap or can remain on the stack. The compiler performs this analysis during the middle-end optimization phase in cmd/compile/internal/escape to minimize garbage collection overhead. You can inspect the compiler's decisions by running your build with the -m flag:

go build -m -gcflags="-m" main.go

This outputs lines like can inline or escaping to heap explaining why specific variables were promoted to the heap.

Escape analysis is a compiler check that decides if a piece of data lives on the fast stack or the slower heap. It matters because heap-allocated data requires garbage collection, which slows down your program. Think of it like a stage manager deciding if an actor stays on stage (stack) or needs to go to the dressing room (heap) based on how long they need to be in the scene.