CODEWITHSUNDEEP
gopointersmemory-managementscope
demi
demi

Reputation: 5504

Return pointer to local struct

I see some code samples with constructs like this:

type point struct {
  x, y int
}

func newPoint() *point {
  return &point{10, 20}
}

I have C++ background and it seems like error for me. What are the semantic of such construct? Is new point allocated on the stack or heap?

Upvotes: 116

Views: 35632

Answers (2)

masebase
masebase

Reputation: 5175

The Golang "Documentation states that it's perfectly legal to return a pointer to local variable." As I read here

https://groups.google.com/forum/?fromgroups=#!topic/golang-nuts/EYUuead0LsY

I looks like the compiler sees you return the address and just makes it on the heap for you. This is a common idiom in Go.

Upvotes: 21

Lily Ballard
Lily Ballard

Reputation: 185681

Go performs pointer escape analysis. If the pointer escapes the local stack, which it does in this case, the object is allocated on the heap. If it doesn't escape the local function, the compiler is free to allocate it on the stack (although it makes no guarantees; it depends on whether the pointer escape analysis can prove that the pointer stays local to this function).

Upvotes: 138

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