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4377 :: Error with Glew

• DTxplorer (orginal) [2018-11-13T23:16:23+01:00] view original

  Sorry for the boring topic. I'm writing a side project for fun using Glew and Glfw. And I encounter an external compiler error.

  A test file who reproduces the error.

  const
      GLFW_CONTEXT_VERSION_MAJOR = 0x00022002
      GLFW_CONTEXT_VERSION_MINOR = 0x00022003
      GLFW_OPENGL_PROFILE = 0x00022008
      GLFW_OPENGL_CORE_PROFILE = 0x00032001
  
  proc glfwInit*():cint {.header: "GLFW/glfw3.h".}
  
  proc glfwCreateWindow*(width, height:int, title:cstring = "GLFW Window", monitor:pointer = nil,
      share:pointer = nil):pointer {.header: "GLFW/glfw3.h".}
  
  proc glfwMakeContextCurrent*(window:pointer) {.header: "GLFW/glfw3.h".}
  
  proc glfwSwapInterval*(interval:int) {.header: "GLFW/glfw3.h".}
  
  proc glfwSwapBuffers*(window:pointer) {.header: "GLFW/glfw3.h".}
  
  proc glfwPollEvents*() {.header: "GLFW/glfw3.h".}
  
  proc glfwWindowShouldClose*(window:pointer):cint {.header: "GLFW/glfw3.h".}
  
  proc glfwDestroyWindow*(window:pointer) {.header: "GLFW/glfw3.h".}
  
  proc glfwTerminate*() {.header: "GLFW/glfw3.h".}
  
  proc glfwWindowHint(hint:int, value:int) {.header: "GLFW/glfw3.h".}
  
  proc glewInit():char {.header:"GL/glew.h".}
  
  proc glewGetErrorString(err:char):cstring {.header:"GL/glew.h".}
  
  ###############################################################################
  
  
  var glfwErr = glfwInit()
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3)
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3)
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE)
  var winHandle = glfwCreateWindow(640, 480)
  glfwMakeContextCurrent(winHandle)
  
  var glewErr = glewInit()
  echo glewGetErrorString(glewErr)
  
  while bool(glfwWindowShouldClose(winHandle)) == false:
      glfwSwapBuffers(winHandle)
      glfwPollEvents()
  
  glfwDestroyWindow(winHandle)
  glfwTerminate()
  
  Run

  The command

  
  nim c --passL:'`pkg-config glew --static --cflags --libs`' --passL:'`pkg-config glfw3 --static --cflags --libs`'  test.nim
  
  Run

  The error

  
  Error: execution of an external compiler program 'gcc -c  -w -I ../Src/GlLoader/Glad  -I/home/drit0/Programmes/Nim/nim-0.19.0/lib -o /home/drit0/.cache/nim/test_d/test.c.o /home/drit0/.cache/nim/test_d/test.c' failed with exit code: 1
  
  In file included from /home/drit0/.cache/nim/test_d/test.c:12:
  /usr/include/GL/glew.h:85:2: error: #error gl.h included before glew.h
   #error gl.h included before glew.h
    ^~~~~
  /usr/include/GL/glew.h:97:2: error: #error glext.h included before glew.h
   #error glext.h included before glew.h
    ^~~~~
  
  Run

  How the hell it is possible to include gl twice here ? In glew there is a flag called "glewExperimental" and I would try to set it to true but I don't know how to import that in Nim.

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• treeform (orginal) [2018-11-13T23:55:22+01:00] view original

  I bet glfw3.h includes gl.h before you include glew.h. You could move the "glewInit" function first. Or create hacky {.emit.} and order the imports manually. This is all C crazyness nim is trying to get a way from.

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• DTxplorer (orginal) [2018-11-14T11:19:39+01:00] view original

  Thanks for the answer. I found a workaround by creating this c file who does the includes.

  #ifndef C_INCLUDES
  #	define C_INCLUDES
  
  #	include "GL/glew.h"
  #	include "GLFW/glfw3.h" //glfw3 must be the last include
  
  #endif
  Run

  I added this command before the nim command to create a library.

  
  gcc -Wall -c c_includes.c
  Run

  In the nim test file I added {.link: "c_includes.o".} and I replaced all the header pragmas by {.importc.} then I run the nim command as in my previous post.

  The program works as expected but I didn't compare the executable size with this solution because I'm not able to compile the first version of my test file. Feel free to answer if you don't like this workaround.

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• treeform (orginal) [2018-11-15T22:15:53+01:00] view original

  Yeah that is the right idea. I think you did it very complicated. I would just put:

  
  {.emit:"""
  #include "GL/glew.h"
  #include "GLFW/glfw3.h" //glfw3 must be the last include
  """.}
  Run

  At the top of your main file.

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