Analysis of the mechanism of memory usage of formal parameters in Go language

Go language formal parameters allocate memory on the function stack: value transfer mechanism: the formal parameter is a copy of the source value, and the original value will not be modified. Memory allocation: The memory size allocated by formal parameters depends on the data type, for example: Basic data type: predefined size Pointer type: 8 bytes Structure type: sum of member variable memory Slice type: 24 bytes (length, capacity and pointer Underlying array) map type: 8 bytes (pointing to the underlying hash table)

Mechanism analysis of formal parameter memory occupation in Go language

Introduction

Formal parameters in Go language allocate memory during function execution. Understanding the memory usage of formal parameters is important to writing efficient code. This article will delve into the mechanism of formal parameter memory usage and illustrate it through a practical case.

Pass by value vs Pass by reference

The Go language uses the pass by value mechanism, which means that the formal parameters passed to the function are copies of the source values. The original value is not modified unless the copy is explicitly modified.

Formal parameter memory usage

Formal parameters allocate memory in the function stack. The stack is a first-in, last-out data structure. The stack is used to manage local variables when a function is executed. The size of memory allocated for a formal parameter depends on its data type.

• Basic data types (such as int, float64) occupy a predefined memory size.
• Pointer types (such as *int) occupy 8 bytes of memory because Go language pointers are always 8 bytes.
• The structure type occupies the sum of the memory of its member variables.
• The slice type occupies 24 bytes of memory: 8 bytes for length, 8 bytes for capacity, and 8 bytes for pointing to the underlying array.
• The map type occupies 8 bytes of memory to point to the underlying hash table.

Practical case

Consider the following code:

func add(x, y int) {
  x += y
}

func main() {
  a, b := 10, 5
  add(a, b)
}

In this case, add formal parameters of the function x and y are allocated on the function stack. They occupy 4 bytes and 4 bytes of memory respectively. During function execution, modifications to x only affect the copy within the function and will not affect the original value a in the main function.

Conclusion

Understanding the mechanism of parameter memory usage is crucial to writing efficient Go language code. The Go language provides effective control over memory management by using passing by value and allocating memory on the function stack.

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