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Memory Layout of Go Closures
Unlike closures in some other languages, Go closures are straightforward heap-allocated structures. They enable functions to capture and retain access to variables defined in enclosing scopes.
Consider the following Go closure:
<code class="go">type M int func (m *M) Adder(amount int) func() { return func() { *m = *m + amount } }</code>
Memory Allocation for Closures
When a closure is created, two memory allocations occur:
In this example, the closure captures the pointer m and an amount variable. Memory allocation for the closure would look as follows:
struct { F uintptr b [8]byte } [8]byte
Memory Footprint of Returned Function
The returned function is itself a thin wrapper that simply calls the closure structure's function pointer. It occupies a negligible amount of memory, typically just the size of a function pointer on the underlying architecture.
Additional Memory Considerations
When multiple closures share the same captured variables, they allocate the memory block only once, even if the closures are defined in different functions. This optimization reduces memory overhead.
In Go, closures promote the discipline of using the heap for long-lived values, ensuring proper memory management and garbage collection.
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