英文:
Why a constant escapes to heap in golang?
问题
这是我用Golang编写的将键C设置为值1的Redis代码。
它使用第三方代码连接到Redis。
package main
import (
"github.com/garyburd/redigo/redis"
)
func main() {
c, err := redis.Dial("tcp", ":6379")
_, err = c.Do("SET", "C", 1)
if err != nil {
panic(err)
}
}
在执行go build -gcflags "-m -m"时，报告如下：
./del.go:41: 1逃逸到堆上
./del.go:41: 从c.Do("SET", "C", 1)（间接调用的参数）到./del.go:41
为什么1会逃逸到堆上？它只是一个简单的常量，在编译时完全知道其完整信息，并且在64位系统上只占用64位。为什么它需要存储在堆内存中？
英文:
Here is my golang code to set a key C to value 1 in redis
It uses third party code in order to connect to redis.
package main
import (
"github.com/garyburd/redigo/redis"
)
func main() {
c, err := redis.Dial("tcp", ":6379")
_, err = c.Do("SET", "C", 1)
if err != nil {
panic(err)
}
}
On doing go build -gcflags "-m -m", it reports
> ./del.go:41: 1 escapes to heap
>
> ./del.go:41: from c.Do("SET", "C", 1) (parameter to indirect call) at
> ./del.go:41
Why does 1 escape to the heap ? It is a simple constant whose complete information is known at compile time and it takes just 64bits on a 64bit system. Why should it be stored in heap memory?
答案1
得分: 13
Do的签名是：
Do(commandName string, args ...interface{}) (reply interface{}, err error)
因为args是一个可变参数（interface{}的切片），它在堆上分配内存。
我相信在未来的Go版本中，对于像这样的简单情况可能会有一些优化措施：https://github.com/golang/go/issues/15528
英文:
The signature of Do is:
Do(commandName string, args ...interface{}) (reply interface{}, err error)
Because args is a variadic (slice of) interface{} it's heap allocated.
I believe there could be some optimisations in the pipeline for simple cases like this in future versions of Go: https://github.com/golang/go/issues/15528
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