gistfile1.cpp

// The native handle type holds resource handles and a coarse description.
typedef union {
   // handle that is a texture
   struct {
      GLuint gl;
      GLuint gl_renderbuf;
   } tex;

   // handle that is a vertex buffer
   struct {
      GLuint base;
      GLuint indices;
   } vbuf;
} GDrawNativeHandle;

// ...

static void eat_gl_err(void)
{
   while (glGetError() != GL_NO_ERROR);
}

static void opengl_check(void)
{
   GLint e = glGetError();
   if (e != GL_NO_ERROR) {
      report_err(e); // prints a message and exits in my test
      eat_gl_err();
   }
}

// ...

static void api_free_resource(GDrawHandle *r)
{
   if (!r->cache->is_vertex) { // <- is_vertex was not set for VBOs here
      // so VBOs went through here...
      glDeleteTextures(1, &r->handle.tex.gl);
      if (r->handle.tex.gl_renderbuf && r->handle.tex.gl_renderbuf != r->handle.tex.gl)
         glDeleteRenderbuffers(1, &r->handle.tex.gl_renderbuf);
   } else {
      // ...instead of through here, generating glDeleteTextures/glRenderbuffers for then-unassigned names.
      glDeleteBuffers(1, &r->handle.vbuf.base);
      glDeleteBuffers(1, &r->handle.vbuf.indices);
   }
   opengl_check(); // <- no error reported here, driver crashes in second thread a while later.
}