开始：了解字符串

Question

I got slightly confused this morning when the following code worked.

// s points to an empty string in memory
s := new(string)

// assign 1000 byte string to that address
b := make([]byte, 0, 1000)
for i := 0; i < 1000; i++ {
    if i%100 == 0 {
        b = append(b, '
')
    } else {
        b = append(b, 'x')
    }
}
*s = string(b)

// how is there room for it there?
print(*s)

http://play.golang.org/p/dAvKLChapd

I feel like I'm missing something obvious here. Some insight would be appreciated.

Answer 1

I hope I understood the question...

An entity of type string is implemented by a run time struct, roughly

type rt_string struct {
        ptr *byte // first byte of the string
        len int   // number of bytes in the string
}

The line

*s = string(b)

sets a new value (of type rt_string) at *s. Its size is constant, so there's "room" for it.

More details in rsc's paper.