golang 为什么比较两个指向结构的变量表现不同？

Question

我创建了两个相同结构的实例，当我比较两个变量指向结构的实例时，对输出感到困惑。

package main

import "fmt"

type Person struct {
    name string
}

func main() {
   p1 := &Person{name: "guru"}
   p2 := &Person{name: "guru"}
   fmt.Println(p1 == p2) // false, compares by address?
   p3 := Person{name: "guru"}
   p4 := Person{name: "guru"}
   fmt.Println(p3 == p4) // true , why? compares by content?
}

== 运算符是否像重载运算符一样工作？

Answer 1

p1 == p2是指针比较，比较指针值(内存地址)。由于您使用了 2 个复合文字(并获取了它们的地址)，它们将指向 2 个不同的变量，因此地址将不同(因为 Person 的大小不为零)。 Spec: Composite literals:

Taking the address of a composite literal generates a pointer to a unique variable initialized with the literal's value.

p3 == p4 比较结构值，它逐个字段地比较它们，并且由于匹配的字段具有相等的值，比较结果将是 true。

比较规则在Spec: Comparison operators :

The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows:

• [...]
• Pointer values are comparable. Two pointer values are equal if they point to the same variable or if both have value nil. Pointers to distinct zero-size variables may or may not be equal.
• [...]
• Struct values are comparable if all their fields are comparable. Two struct values are equal if their corresponding non-blank fields are equal.