*mix.Chunk.setVolume() fails on Windows 7

[ghost]

So I finally got everything compiling and running under Windows (Win 7 32 bit using MSYS and MinGW). However, one function call causes a cgo exception with the following output:

Exception 0xc0000005 0x0 0xc 0x6788777b
PC=0x6788777b
signal arrived during cgo execution

github.com/veandco/go-sdl2/sdl_mixer._Cfunc_Mix_VolumeChunk(0x0, 0x63, 0x0)
    C:/dev/golang/src/github.com/veandco/go-sdl2/sdl_mixer/:443 +0x3f
github.com/veandco/go-sdl2/sdl_mixer.(*Chunk).SetVolume(0x0, 0x63, 0x115cff24)
    C:/dev/golang/src/github.com/veandco/go-sdl2/sdl_mixer/sdl_mixer.go:270 +0x30
main.initAudio()
    C:/dev/01_hello_SDL/revenge-of-the-gopher/src/audio.go:27 +0x162
main.main()
    C:/dev/01_hello_SDL/revenge-of-the-gopher/src/main.go:35 +0xf7

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
    c:/go/src/runtime/asm_386.s:2287 +0x1
eax     0x0
ebx     0x0
ecx     0x5ab440
edx     0x63
edi     0x115d0000
esi     0x5a36c0
ebp     0x5a38e0
esp     0x12fe98
eip     0x6788777b
eflags  0x210206
cs      0x1b
fs      0x3b
gs      0x0
exit status 2

The offending function looks like this:

var gameAudio audio

type audio struct {
explode1, laser1, playerDeath *mix.Chunk
enemyHit, powerUp1Active      *mix.Chunk
intro, bgmusic                *mix.Music
}

func initAudio() {
mix.OpenAudio(22050, mix.DEFAULT_FORMAT, 2, 4096)

gameAudio = audio{
    explode1:       mix.LoadWAV("assets/SFX_Explosion_01.ogg"),
    laser1:         mix.LoadWAV("assets/Laser1.ogg"),
    playerDeath:    mix.LoadWAV("assets/player_death.ogg"),
    enemyHit:       mix.LoadWAV("assets/enemy_hit.ogg"),
    powerUp1Active: mix.LoadWAV("assets/powerup1_active.ogg"),

    bgmusic: mix.LoadMUS("assets/bgmusic1.ogg"),
    intro:   mix.LoadMUS("assets/bgmusic6.ogg"),
}

gameAudio.enemyHit.SetVolume(100)
gameAudio.laser1.SetVolume(20)
gameAudio.playerDeath.SetVolume(75)
}

Line 27 in audio.go refers to the line containing "gameAudio.enemyHit.SetVolume(100)".

The entire project is available here: https://github.com/Decker108/revenge-of-the-gopher/tree/060094c0d2140bf9dacd10a4485c97813b49134f

[akovaski]

Your LoadWAV calls are probably failing (at least it is for your project on my machine). Check that gameAudio.enemyHit et al. are not nil.

I suspect that your sdl_mixer installation is not built with ogg support.

That being said, perhaps some changes should be made to the sdl_mixer library:

• This is an unpleasant way to crash... a nil check in the Chunk methods might be a worthwhile investment

  • This version of SetVolume() would result in a nil-pointer panic instead of the somewhat cryptic panic it currently does

  func (chunk Chunk) SetVolume(volume int) int {
      _chunk := (*C.Mix_Chunk)(unsafe.Pointer(&chunk))
      _volume := (C.int)(volume)
      return (int)(C.Mix_VolumeChunk(_chunk, _volume))
  }

• It's hard to tell what's wrong with loading the file (can it not find the file? is the filetype not supported?) without Mix_GetError

  • What LoadWav() with error checking could look like

  func LoadWAV(file string) (c *Chunk, err error) {
      _file := C.CString(file)
      defer C.free(unsafe.Pointer(_file))
      _rb := C.CString("rb")
      defer C.free(unsafe.Pointer(_rb))
  
      rwFile := C.SDL_RWFromFile(_file, _rb)
      if rwFile == nil {
          return nil, errors.New(C.GoString(C.Mix_GetError()))
      }
  
      c = (*Chunk)(unsafe.Pointer(C.Mix_LoadWAV_RW(rwFile, 1)))
      if c == nil {
          return nil, errors.New(C.GoString(C.Mix_GetError()))
      }
      return c, nil
  }

Please try using this version of LoadWAV to see if your files are not being loaded. (the "errors" package must also be imported in sdl_mixer.go)

[ghost]

Sorry, I screwed up. I built the game with go run outside the game folder... and then it couldn't find the asset files and threw this exception.

More idiomatic error handling for sdl_mixer would be a nice thing though :)

I implemented your loadWav function and got this output:
2015/03/03 19:38:40 Couldn't open assets/SFX_Explosion_01.ogg
exit status 1

Which of course make sense since the application is run from outside the intended folder.

I'm closing this issue as "error exists between keyboard and chair".

[krux02]

actually I am writing at the moment more ideomatic error for the mixer. But it's a compatibility changing. Especially SetVolume is now called like the original function just Volume, because it's also the getter.