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896 :: Passing NULL pointers to a C library function?

• kragil (orginal) [2015-02-19T18:20:43+01:00] view original

  I made quite a lot of progress today, but now I have reached a roadblock. I am probably too thick and newb, but how do I use queryTexture from the SDL2 Wrapper:

  proc queryTexture*(texture: TexturePtr; format: ptr uint32; access, w, h: ptr cint): SDL_Return {.discardable, importc: "SDL_QueryTexture".}

  How do I pass NULL? The compiler won't allow anything. I tried: sdl2.queryTexture(pTexture, NULL ,NULL, castcint, castcint)

  PS. I also tried {.extern: NULL} and I casting unit32 to pointer and some even more stupid stuff, but nothing works. Yeah and I read the tutorials and the manual and Nim for C programmers, but I did not find an answer.

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• andrea (orginal) [2015-02-19T18:24:43+01:00] view original

  Have you tried nil?

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• kragil (orginal) [2015-02-19T18:57:51+01:00] view original

  Yeah, not working.

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• OderWat (orginal) [2015-02-19T19:02:47+01:00] view original

  Tried: castWhatCompilerWants

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• def (orginal) [2015-02-19T19:57:10+01:00] view original

  Works fine for me:

  import sdl2
  
  var
    texture: TexturePtr
    width: cint = 10
    height: cint = 20
  
  queryTexture(texture, nil, nil, addr width, addr height)
  Run

  Note the cint and addr.

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• kragil (orginal) [2015-02-19T20:18:40+01:00] view original

  I didn't know about addr! So that was the problem. Thanks! (Maybe the pointer/memory handling should get its own doc article)

  Thanks again.

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