SDL3 fails to create OpenGL ES 2.0 context?

I am working on an OpenGL project using the SDL3 and OpenGL ES 2.0. For the moment, I have a basic code which creates a window with the drawing of a triangle. The issue here is that the glCreateShader(GL_VERTEX_SHADER) function always returns 0.

The reason of this is that the context is not created, or not being used. For example, if I run the following code:

#include <stdio.h>
#include <stdlib.h>
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>
#include <SDL3/SDL_opengles2.h>

int main(int argc, char* argv[]) {
    // Initialize SDL2

    if (!SDL_Init(SDL_INIT_VIDEO)) {
        printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
        return -1;
    }

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);

    // Create an SDL window with OpenGL ES context
    SDL_Window* window = SDL_CreateWindow("OpenGL ES 2.0 Triangle", 800, 600, SDL_WINDOW_OPENGL);
    if (!window) {
        printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }

    SDL_GLContext context = SDL_GL_CreateContext(window);

    if (!context) {
        printf("OpenGL context could not be created! SDL_Error: %s\n", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return -1;
    }

    int isMadeCurrent = SDL_GL_MakeCurrent(window, context);

    printf("Current context? %d\n", isMadeCurrent);
    printf("Context error: %s\n", SDL_GetError());
    printf("Context version: %s\n", glGetString(GL_VERSION));

    SDL_GL_DestroyContext(context);
    SDL_DestroyWindow(window);
    SDL_Quit();

    printf("Exiting...\n");

    return 0;
}

I get the following output:

Current context? 1
Context error:
Context version: (null)
Exiting...

glGetString(GL_VERSION) printing (null) means that it couldn't check the version of OpenGL since there is no current context, despite there are no errors shown. I know SDL_GL_MakeCurrent() is not a necessary line, but I have included to make sure the context is being used, which does not seem to be the case.

My directory structure is the following:

- src
  - include
    - GLES2
    - SDL3
  - lib
    - libGLESv2.lib
    - libSDL3.dll.a
- libGLESv2.dll
- main.c
- main.exe
- Makefile
- mozglue.dll
- SDL3.dll

Here is the content of my Makefile (I compile everything in Windows with mingw32-make:

all:
    gcc -Isrc/include -L src/lib -o main main.c -lGLESv2 -lSDL3

I have tried in a separate project using SDL2 instead of SDL3, or compiling and then running my code in another system. None of this fixed this issue. Also, I made sure the libraries included are compatible with the architecture of my computer.

Solution

Works On My Machine™ with both Mesa's EGL+GLES implementation (llvmpipe software rasterizer) via pal1000's Windows binaries (SDL_OPENGL_ES_DRIVER=1 + GALLIUM_DRIVER=llvmpipe).

>set SDL_OPENGL_ES_DRIVER=1
>set GALLIUM_DRIVER=llvmpipe
>sdl-gles.exe
Current context? 1
GL_VERSION : OpenGL ES 3.2 Mesa 24.3.4 (git-1950a8b78c)
GL_VENDOR  : Mesa
GL_RENDERER: llvmpipe (LLVM 19.1.7, 256 bits)

...and AMD's hardware GLES implementation via the GLES-on-WGL code-path (SDL_OPENGL_ES_DRIVER=0):

>set SDL_OPENGL_ES_DRIVER=0
>sdl-gles.exe
Current context? 1
GL_VERSION : OpenGL ES 2.0.0 23.10.18.05.230719
GL_VENDOR  : ATI Technologies Inc.
GL_RENDERER: AMD Radeon Pro WX 3200 Series

Plus GLAD for runtime OpenGL loading.

All together:

#include <stdio.h>
#include <stdlib.h>
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>
#include <glad/gles2.h>

int main(int argc, char* argv[]) {
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
        return -1;
    }

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);

    // Create an SDL window with OpenGL ES context
    SDL_Window* window = SDL_CreateWindow("OpenGL ES 2.0 Triangle", 800, 600, SDL_WINDOW_OPENGL);
    if (!window) {
        printf("Window could not be created! SDL_Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }

    SDL_GLContext context = SDL_GL_CreateContext(window);

    if (!context) {
        printf("OpenGL context could not be created! SDL_Error: %s\n", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return -1;
    }

    int isMadeCurrent = SDL_GL_MakeCurrent(window, context);

    gladLoadGLES2( SDL_GL_GetProcAddress );

    printf("Current context? %d\n", isMadeCurrent);
    printf("GL_VERSION : %s\n", glGetString(GL_VERSION));
    printf("GL_VENDOR  : %s\n", glGetString(GL_VENDOR));
    printf("GL_RENDERER: %s\n", glGetString(GL_RENDERER));

    SDL_GL_DestroyContext(context);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

Tied together using CMake:

cmake_minimum_required( VERSION 3.7.0 )
project( sdl-gles )

set( SDL_STATIC ON CACHE BOOL "" FORCE )
set( SDL_SHARED OFF CACHE BOOL "" FORCE )
set( SDL_TESTS OFF CACHE BOOL "" FORCE )
set( SDL_TEST_LIBRARY OFF CACHE BOOL "" FORCE )
add_subdirectory( external/sdl EXCLUDE_FROM_ALL )

include_directories( "include" )
add_executable( sdl-gles "src/main.c" "src/gles2.c" )
target_link_libraries( sdl-gles PRIVATE SDL3::SDL3-static)