Segfault: C 'get_exts()' doesn't differenciate OpenGL context from OpenGLES one

[0x1100]

I generate glad for OpenGL 3.0 and Open GL ES 2.0 (--api=gl=3.0,gles2=2.0).
Calling gladLoadGLES2Loader within an Open GL ES 3.0 context causes a segfault in get_exts by trying to call glGetStringi and glGetIntegerv (both NULL pointers) instead of glGetString.

Those functions aren't supposed to be loaded. get_exts uses them because of the 3.0 context without considering if we're given an OpenGL or an OpenGL ES one.

This could be considered a follow up of issue #6.

[Dav1dde]

This should not happen, get_exts checks for GLVersion.major < 3, gladLoadGLES2Loader resets the value before calling get_exts, the only issue I can see is if glGetString(GL_VERSION) returns a version > 3 on your ES context.

I am also not sure how to fix this, maybe introduce GL.Version.someNewVersion boolean which only gets set if the loaded version is >= 3 and Glad was built to load >= 3.

[Dav1dde]

Can you paste the result of glGetString(GL_VERSION) after setting up the ES context please?

Is it possible that you use a OpenGL ES context >= 3, but only built Glad to support 2.0?

EDIT: Small update, I figured out why this happens and that this should infact not happen, I will push a fix later tonight.

[Dav1dde]

Thanks for the report!

Please test with current master and report back, I reproduced this locally and it seems to be fixed. I will push a new version if you give the ok ;).

[0x1100]

It's not fixed on my side...

I built for GL3 and ES2 ; then I ask for an ES 2.0 context to SDL2 but I get an ES 3.0 one. (I don't think it's a bug since there is backwards compatibility.)

I put the code generated by glad below. Currently, get_exts uses glGetIntegerv/glGetStringi if:

• (defined(GL_ES_VERSION_3_0) or defined(GL_VERSION_3_0)) and `GLversion.major >= 3

Instead, we need to check if we get one of those:

• 'context is GLES' and defined(GL_ES_VERSION_3_0) and GLversion.major >= 3
• 'context is GL' and defined(GL_VERSION_3_0) and GLversion.major >= 3

Currently, get_exts choses to use glGetIntegerv/glGetStringi instead of glGetString because (defined(GL_VERSION_3_0) and GLversion.major >= 3) yet it shouldn't because ('context is GLES' and not defined(GL_ES_VERSION_3_0)).

I don't really get those two new variables (max_loaded_major, max_loaded_minor). Instead, I think that adding a mere parameter to get_exts (gl/gles) may do the trick.

#if defined(GL_ES_VERSION_3_0) || defined(GL_VERSION_3_0)
#define _GLAD_IS_SOME_NEW_VERSION 1
#endif

static int max_loaded_major;
static int max_loaded_minor;

static const char *exts = NULL;
static int num_exts_i = 0;
static const char **exts_i = NULL;

static void get_exts(void) {
#ifdef _GLAD_IS_SOME_NEW_VERSION
    if(max_loaded_major < 3) {
#endif
        exts = (const char *)glGetString(GL_EXTENSIONS);
#ifdef _GLAD_IS_SOME_NEW_VERSION
    } else {
        int index;

        num_exts_i = 0;
        glGetIntegerv(GL_NUM_EXTENSIONS, &num_exts_i);
        if (num_exts_i > 0) {
            exts_i = (const char **)realloc((void *)exts_i, num_exts_i * sizeof *exts_i);
        }

        for(index = 0; index < num_exts_i; index++) {
            exts_i[index] = (const char*)glGetStringi(GL_EXTENSIONS, index);
        }
    }
#endif
}

[Dav1dde]

Please try again, I accidently only fixed the same problem with OpenGL contexts.

max_loaded_major/max_loaded_minor are the minimum of the GL/GLES context version and the supported version by glad. So if you get a 3.0 context but glad only supports 2.0 it will only use 2.0 versions (unlike before where it tried to use 3.0 functions which werent loaded).

I thought about clamping GLVersion instead of introducing max_loaded_major/max_loaded_minor but I didn't like that.

[0x1100]

Yep, it works. Thanks!