如何使用gdb调试golang代码查看通道内部内容？

Question

i have this code for example

http://play.golang.org/p/9U22NfrXeq

// A concurrent prime sieve

package main

// Send the sequence 2, 3, 4, ... to channel 'ch'.
func Generate(ch chan<- int) {
    for i := 2; ; i++ {
        ch <- i // Send 'i' to channel 'ch'.
    }
}

// Copy the values from channel 'in' to channel 'out',
// removing those divisible by 'prime'.
func Filter(in <-chan int, out chan<- int, prime int) {
    for {
        i := <-in // Receive value from 'in'.
        if i%prime != 0 {
            out <- i // Send 'i' to 'out'.
        }
    }
}

// The prime sieve: Daisy-chain Filter processes.
func main() {
    ch := make(chan int) // Create a new channel.
    go Generate(ch)      // Launch Generate goroutine.
    for i := 0; i < 10; i++ {
        prime := <-ch
        print(prime, "
")
        ch1 := make(chan int)
        go Filter(ch, ch1, prime)
        ch = ch1
    }
}

How to see what's inside channel? For example I want to debug this line:

prime := <-ch

By typing 'p ch' in gdb only prints address of the channel. How can I get contents?

Answer 1

You just have to dereference ch. With a very small program:

package main

func main() {
    ch := make(chan int, 10)
    ch <- 1
    ch <- 2
    ch <- 4
    <-ch
}

Debugging:

(gdb) p *ch
$1 = struct hchan<int> = {1, 2, 4}