by marius@vastech.co.za:

I have found a strange problem where the format in which a number constant is declared
causes 
deadlock. The same program runs fine with:

const nUM_SERVERS = 10 // works

but crashes with:

const nUM_SERVERS = 1e1 // causes deadlock

The same happens for numbers of any size, even for:

const nUM_SERVERS = 1e0 // causes deadlock

and 

const nUM_SERVERS = 1e6 // causes deadlock

This const is used in only place in the program:

var svrCh [nUM_SERVERS]chan int

The same problem occurs when the relevant literals are used in the var declaration.

The full test program is attached below. 

> hg identify
7a249afa5ed3 tip

GOARCH=amd64
GOOS=darwin

To reproduce the problem:

Comment the nUM_SERVERS declaration at the top of the program as follows:

/*const nUM_SERVERS = 10 // works*/
const nUM_SERVERS = 1e1 // causes deadlock

Compile and run:
6g tstGo.go; 6l tstGo.6; ./6.out

I expect something like the following output:

start of output>

setup complete in  0.000111 s
1000 msgs sent in  0.004202 s

<end of output

The output above was generated by the following constant declaration configuration:

const nUM_SERVERS = 10 // works
/*const nUM_SERVERS = 1e1 // causes deadlock*/

Instead the following output is generated:

setup complete in  4.3e-05 s
throw: all goroutines are asleep - deadlock!

panic PC=0x2c5068
throw+0x3e /Users/marius/local/go/src/pkg/runtime/runtime.c:74
    throw(0x52cc3, 0x0)
nextgandunlock+0x15a /Users/marius/local/go/src/pkg/runtime/proc.c:344
    nextgandunlock()
scheduler+0xe0 /Users/marius/local/go/src/pkg/runtime/proc.c:509
    scheduler()
mstart+0x47 /Users/marius/local/go/src/pkg/runtime/proc.c:400
    mstart()
bsdthread_start+0x14 /Users/marius/local/go/src/pkg/runtime/darwin/amd64/sys.s:148
    bsdthread_start()

goroutine 2 [4]:
gosched+0x4e /Users/marius/local/go/src/pkg/runtime/proc.c:530
    gosched()
runtime.selectgo+0x3d0 /Users/marius/local/go/src/pkg/runtime/chan.c:792
    runtime.selectgo(0x29e400, 0x0)
main.bank+0xee /Users/marius/nextPrj/gotest/tstGo.go:70
    main.bank(0x2a3180, 0x0, 0x2a31e0, 0x0)
goexit /Users/marius/local/go/src/pkg/runtime/proc.c:140
    goexit()
0x2a3180 unknown pc

goroutine 1 [4]:
gosched+0x4e /Users/marius/local/go/src/pkg/runtime/proc.c:530
    gosched()
chanrecv+0x39b /Users/marius/local/go/src/pkg/runtime/chan.c:326
    chanrecv(0x2a3240, 0x0, 0x2a5f10, 0x0, 0x0, ...)
runtime.chanrecv1+0x50 /Users/marius/local/go/src/pkg/runtime/chan.c:423
    runtime.chanrecv1(0x2a3240, 0x0)
main.spray+0x7f /Users/marius/nextPrj/gotest/tstGo.go:35
    main.spray(0x2a3240, 0x0)
main.main+0x270 /Users/marius/nextPrj/gotest/tstGo.go:26
    main.main()
mainstart+0xf /Users/marius/local/go/src/pkg/runtime/amd64/asm.s:54
    mainstart()
goexit /Users/marius/local/go/src/pkg/runtime/proc.c:140
    goexit()


The full test program follows:
tstGo.go:
-------------------------------

package main

import(
    "fmt"
    "time"
)

/*const nUM_SERVERS = 10 // works*/
const nUM_SERVERS = 1e1 // causes deadlock

const nUM_MSGS = 1e3
const cREDIT = 30
var svrCh [nUM_SERVERS]chan int

func main() {
    startTime := time.Nanoseconds()
    bankReqCh := make(chan *reqCredit)
    bankRelCh := make(chan int)
    go bank(bankReqCh, bankRelCh)
    respCh := make(chan int)
    for i := 0; i < len(svrCh); i++ {
        svrCh[i] = make(chan int)
        go svr(i, svrCh[i], respCh, bankReqCh, bankRelCh)
    }
    fmt.Println("setup complete in ", float64(time.Nanoseconds()-startTime)/1.0e9, "s")
    spray(respCh)
}

func spray(respCh chan int) {
    startTime := time.Nanoseconds()
    for i := 0; i < len(svrCh); i++ {
        svrCh[i] <- 1
    }
    for numMsgs := 0; numMsgs < nUM_MSGS; {
        svr := <- respCh
        numMsgs++
        svrCh[svr] <- 1
    }
    fmt.Println(nUM_MSGS, "msgs sent in ", float64(time.Nanoseconds()-startTime)/1.0e9, "s")
}

func svr(id int, clientReq chan int, clientRsp chan int, bankReq chan *reqCredit,
bankRel chan int) 
{
    reply := make(chan int)
    req := reqCredit{reply, 1}

    for {
        <- clientReq
        bankReq <- &req
        credit := <- reply
        bankRel <- credit
        clientRsp <- id
    }
}

type reqCredit struct {
    replyTo chan int
    credit  int
}

func bank(request chan *reqCredit, release chan int) {
    credit := cREDIT
    for {
        if credit > 0 {
            select {
                case req := <- request:
                    credit -= req.credit
                    req.replyTo <- req.credit
                case c := <- release:
                    credit += c
            }
        }else{
            c := <- release
            credit += c
        }
    }
}