I have started learning engine development and have decided to use GLAD and SDL2 for my project. I have followed various tutorials and have successfully linked both SDL2 and GLAD to my project. But I have encountered a very strange problem.
I tried to use the glGenBuffers() function but Visual Studio told me glGenBuffers is undefined. So I went into the glad.h and searched for glGenBuffers and found it inside of #ifndef GL_VERSION_1_5. (I could not use any other functions as well.)
So I tried to comment out the #ifndef and #endif for that part and now it worked! I could use glGenBuffers. And beacuse I know I have version 4.6 of opengl I don't have to worry about the versions.
The problem here is that this feels like I am not doing it like it's supposed to, and that this might introduce problems in the future. So what I did was I put the #ifndef and #endif back into it's place. But now the glad.h was absolutely littered with multiple errors of these types:
this declaration has no storage class or type specifier
the #if for this directive is missing
the #endif for this directive is missing
The document was exactly the same as when I got it, but what was even more strange was that now every other function worked as well. Even those not in the #ifndef GL_VERSION_1_5 but for example #ifndef GL_VERSION_3_0.
And the code in the main.cpp still compiled and ran fine. When I collapse the #ifndef GL_VERSION_1_5 it now says "Active Preprocessor Block" as well, wheras the others say "Inactive Preprocessor Block".
I tried replacing the document with another copy and now I am back to the old problem of it stating glGenBuffers is undefined. It's worth noting gladLoadGLLoader(( GLADloadproc )SDL_GL_GetProcAddress) works fine at runtime so it's not a problem with GLAD itself.
Anyone know what might be causing this and how I should go about solving this problem?
The includes I'm currently using:
#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>
#include <glad/glad.h>
Compile log:
Build started...
1>------ Build started: Project: GrubEngineC++, Configuration: Debug x64 ------
1>GrubEngineC++.cpp
1>C:\Users\Arbeit\Desktop\C++ Engine\GEC\GrubEngineC++\include\glad\glad.h(873,1): warning C4005: 'GL_INVALID_INDEX': macro redefinition
1>C:\Users\Arbeit\Desktop\C++ Engine\GEC\SDL2\include\SDL_opengl_glext.h(1651): message : see previous definition of 'GL_INVALID_INDEX'
1>C:\Users\Arbeit\Desktop\C++ Engine\GEC\GrubEngineC++\include\glad\glad.h(915,1): warning C4005: 'GL_TIMEOUT_IGNORED': macro redefinition
1>C:\Users\Arbeit\Desktop\C++ Engine\GEC\SDL2\include\SDL_opengl_glext.h(1726): message : see previous definition of 'GL_TIMEOUT_IGNORED'
1>C:\Users\Arbeit\Desktop\C++ Engine\GEC\GrubEngineC++\GrubEngineC++.cpp(15,5): error C3861: 'glGenBuffers': identifier not found
1>Done building project "GrubEngineC++.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
The problem is the include order for the OpenGL definitions. As can be seen in the compile log, there are also other definitions like GL_INVALID_INDEX that are already defined when glad is included.
The SDL_opengl.h is the OpenGL header for SDL and already contains the definitions for a lot of the OpenGL related symbols and conflicts with the use of glad.h. You either have to include it after glad.h or not all (which is better, unless you need methods from SDL_opengl.h.