Error imgui GLSL 4.40

[Zukhruf]

Version: 1.69
Branch: master

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_opengl3.cpp + imgui_impl_sdl.cpp
Compiler: Visual Studio, C++ 11
Operating System: windows 10

My Issue/Question:

I Try to add GUI on my animation engine program. But when adding ImGui for opengl3 sdl2, I always have error at glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);, and the error says, Access violation executing location 0x0000000000000000. Before adding imgui, my program works fine. I search some solution on the internet, but none of those are works.

Screenshots/Video

Standalone, minimal, complete and verifiable example:

bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
{
    // Backup GL state
    GLint last_texture, last_array_buffer;
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer); <-- Error at this line
#ifndef IMGUI_IMPL_OPENGL_ES2
    GLint last_vertex_array;
    glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
#endif 
}

[ocornut]

You have probably not initialized the GL functions pointers of the GL function loaders that is used by imgui_impl_opengl3.cpp (by default we use gl3w)

[ocornut]

I made a few changes to imgui_impl_opengl3.cpp to help users understand what they have made this mistake of not initializing the GL function loader.

Please refer to the examples/ main.cpp files for a working application.

[Jaumeavinyo]

Hi! have a similar problem with gladLoadGL() wich now i sopose it is called gladLoadGLLoader() as I can see in glad.c. My problem is a access violation with the variable "last_active_texture". the thing is that after adding gladloader in my code, The problem persist

ERROR HERE
gladLoadGL screenshot

[ocornut]

@Jaumeavinyo What's your version and the most recent date at the top of your imgui_impl_opengl3.cpp ?
Can you step in ImGui_ImplOpenGL3_Init() and confirm the values of GlVersion and the value of the gl_loader string defined near the end of that function?

[Jaumeavinyo]

I downloaded the 1.81 imGui release from your repo. The most recent date in the change log of the file imgui_impl_opengl3.cpp is:
// 2021-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
// 2021-01-03: OpenGL: Backup, setup and restore GL_STENCIL_TEST state.

the glsl version string is: "#version 130" and the value of the gl_loader string is unknown because I don't really think I understand where does the inside function of the loader get the string from

image here

[Jaumeavinyo]

pd: thanks for the hyper fast attention to my post!

[ocornut]

The code in ImGui_ImplOpenGL3_Init() has this block:

    // Debugging construct to make it easily visible in the IDE and debugger which GL loader has been selected.
    // The code actually never uses the 'gl_loader' variable! It is only here so you can read it!
    // If auto-detection fails or doesn't select the same GL loader file as used by your application,
    // you are likely to get a crash below.
    // You can explicitly select a loader by using '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
    const char* gl_loader = "Unknown";
    IM_UNUSED(gl_loader);
#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
    gl_loader = "GL3W";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
    gl_loader = "GLEW";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
    gl_loader = "GLAD";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
    gl_loader = "GLAD2";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
    gl_loader = "glbinding2";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
    gl_loader = "glbinding3";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
    gl_loader = "custom";
#else
    gl_loader = "none";
#endif

You want to step at the end of this block and check the exact version for gl_loader. If it isn't "GLAD" or "GLAD2" then the compile-time configuration is wrong and the backend doesn't know about your loader so it's going to try accessing the function symbols from another loader which wasn't initialized.

[Jaumeavinyo]

Here you have it. Thanks

// Debugging construct to make it easily visible in the IDE and debugger which GL loader has been selected.
// The code actually never uses the 'gl_loader' variable! It is only here so you can read it!
// If auto-detection fails or doesn't select the same GL loader file as used by your application,
// you are likely to get a crash below.
// You can explicitly select a loader by using '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
const char* gl_loader = "Unknown";
IM_UNUSED(gl_loader);
#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
gl_loader = "GL3W";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
gl_loader = "GLEW";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
gl_loader = "GLAD";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
gl_loader = "GLAD2";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
gl_loader = "glbinding2";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
gl_loader = "glbinding3";
#elif defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
gl_loader = "custom";
#else
gl_loader = "none";
#endif

[Jaumeavinyo]

Im using:
gl_loader = "GLAD"

[ocornut]

Your first answer suggest you are misunderstanding my question.
Please use a debugger or add a printf() statement to actually confirm that the runtime value of gl_loader is GLAD.

If you didn't properly set the compile-time option IMGUI_IMPL_OPENGL_LOADER_GLAD or IMGUI_IMPL_OPENGL_LOADER_GLAD2 then the backend code is going to try to detect a loader based on available includes but there's no guarantee it's going to pick the same one ("glad") as you initialized.

[Jaumeavinyo]

here you have it, debuuged and confirmed

[ocornut]

You didn't gave me the GlVersion version, only the GLSLversion one.

[Jaumeavinyo]

You didn't gave me the GlVersion version, only the GLSLversion one.

where do I find this=?

[Jaumeavinyo]

You didn't gave me the GlVersion version, only the GLSLversion one.

here?¿

[ocornut]

In your version of the code there's a variable g_GlVersion setup at the beginning of ImGui_ImplOpenGL3_Init()
I am afraid I can't help further if you are not researching things further and not reading comments.

Also your first screen has some code saying glPushDebugGroup() which is not part of vanilla imgui_impl_opengl3 and was never part of it, and it looks like it may be this function call that crash. So you are using a modified backend so at this point I can't really help debugging random modified code that wasn't provided nor have a justification.

[Jaumeavinyo]

In your version of the code there's a variable g_GlVersion setup at the beginning of ImGui_ImplOpenGL3_Init()
I am afraid I can't help further if you are not researching things further and not reading comments.

Also your first screen has some code saying glPushDebugGroup() which is not part of vanilla imgui_impl_opengl3 and was never part of it, and it looks like it may be this function call that crash. So you are using a modified backend so at this point I can't really help debugging random modified code that wasn't provided nor have a justification.

Okay, you helped a lot, don'tworry I just needed some clues to find where was the problem, pd, my gl version is 320

pd, glPushDebugGroup() is not something I added to the code. I will review what happened thanks