Winapi GetSystemTimes函数未填充lpIdleTime / lpKernelTime / lpUserTime

Question

I`m stuck with GetSystemTimes function. There is no any problem in c++ code, but with golang I'm getting three nils instead of expected values

My code:

package main

import (
    "log"
    "syscall"
    "unsafe"
)

var (
    modKernel32 = syscall.NewLazyDLL("kernel32.dll")
    procGetSystemTimes = modKernel32.NewProc("GetSystemTimes")
)

type SystemTimes struct {
    IdleTime   *syscall.Filetime
    KernelTime *syscall.Filetime
    UserTime   *syscall.Filetime
}

func main() {
    times, err := getSystemTimes()
    if err != nil {
        log.Fatal(err)
    }
    log.Printf("idle=%v, kernel=%v, user=%v", times.IdleTime, times.KernelTime, times.UserTime)
}

func getSystemTimes() (times SystemTimes, err error) {
    res, _, err1 := procGetSystemTimes.Call(uintptr(unsafe.Pointer(times.IdleTime)), uintptr(unsafe.Pointer(times.KernelTime)), uintptr(unsafe.Pointer(times.UserTime)))
    if res != 1 {
        return times, err1
    }
    return
}

It's super simple and very similar to syscall`s GetProcessTimes function from stdlib. And look, what my program prints:

idle=<nil>, kernel=<nil>, user=<nil>

Why? I expect error or result, why my fields are empty?

Confguration: win8 x64, go1.4.2 windows/amd64

Answer 1

You're passing the address of nil fields to the function.

Either make it point directly to the Filetime struct or initialize all 3 fields before passing them:

type SystemTimes struct {
    IdleTime   syscall.Filetime
    KernelTime syscall.Filetime
    UserTime   syscall.Filetime
}
.....
res, _, err1 := procGetSystemTimes.Call(uintptr(unsafe.Pointer(&times.IdleTime)), uintptr(unsafe.Pointer(&times.KernelTime)), uintptr(unsafe.Pointer(&times.UserTime)))

Output:

┌─ oneofone@Oa [/tmp]                                                                                                             
└──➜ env CC=i686-w64-mingw32-gcc CGO_ENABLED=1 GOOS=windows GOARCH=386 go build -a /tmp/syscall.go; and wine syscall.exe
2015/05/09 22:31:53 idle={1292275456 39}, kernel={1436840864 41}, user={3496565408 2}

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