Incomplete extension list?

OpenGL OpenGL: Basic Coding
1

I feel like I’m either missing an important amount of vendor-specific extensions, or else I’m fundamentally misunderstanding the way GL extensions are reported. In particular, I’m trying to use GL_NV_texture_barrier. My understanding is that it’s been adopted as core in 4.5 through GL_ARB_texture_barrier. But shouldn’t GL_NV_texture_barrier still be reported when using getStringi(GL_EXTENSIONS)? Looking at different extension reports online for my current GPU (GeForce GTX 1080), I can definitely see both GL_NV and GL_ARB variants.

In fact, I don’t have a single vendor-specific extension in my extensions list, which I find suspicious considering the amount of Nvidia-specific extensions that haven’t been made core. Out of curiosity, I’ve tried both a Core profile or a Compatibility profile but the extensions reported are the same.

For what it’s worth, here’s the extensions I have access to:

    "GL_ARB_ES2_compatibility"
    "GL_ARB_ES3_1_compatibility"
    "GL_ARB_ES3_compatibility"
    "GL_ARB_arrays_of_arrays"
    "GL_ARB_base_instance"
    "GL_ARB_blend_func_extended"
    "GL_ARB_buffer_storage"
    "GL_ARB_clear_buffer_object"
    "GL_ARB_clear_texture"
    "GL_ARB_clip_control"
    "GL_ARB_color_buffer_float"
    "GL_ARB_compressed_texture_pixel_storage"
    "GL_ARB_compute_shader"
    "GL_ARB_compute_variable_group_size"
    "GL_ARB_conditional_render_inverted"
    "GL_ARB_conservative_depth"
    "GL_ARB_copy_buffer"
    "GL_ARB_copy_image"
    "GL_ARB_cull_distance"
    "GL_ARB_debug_output"
    "GL_ARB_depth_buffer_float"
    "GL_ARB_depth_clamp"
    "GL_ARB_depth_texture"
    "GL_ARB_derivative_control"
    "GL_ARB_direct_state_access"
    "GL_ARB_draw_buffers"
    "GL_ARB_draw_buffers_blend"
    "GL_ARB_draw_elements_base_vertex"
    "GL_ARB_draw_indirect"
    "GL_ARB_draw_instanced"
    "GL_ARB_enhanced_layouts"
    "GL_ARB_explicit_attrib_location"
    "GL_ARB_explicit_uniform_location"
    "GL_ARB_fragment_coord_conventions"
    "GL_ARB_fragment_layer_viewport"
    "GL_ARB_fragment_shader_interlock"
    "GL_ARB_framebuffer_no_attachments"
    "GL_ARB_framebuffer_object"
    "GL_ARB_framebuffer_sRGB"
    "GL_ARB_geometry_shader4"
    "GL_ARB_get_program_binary"
    "GL_ARB_get_texture_sub_image"
    "GL_ARB_gl_spirv"
    "GL_ARB_gpu_shader5"
    "GL_ARB_gpu_shader_fp64"
    "GL_ARB_half_float_pixel"
    "GL_ARB_half_float_vertex"
    "GL_ARB_indirect_parameters"
    "GL_ARB_instanced_arrays"
    "GL_ARB_internalformat_query"
    "GL_ARB_internalformat_query2"
    "GL_ARB_invalidate_subdata"
    "GL_ARB_map_buffer_alignment"
    "GL_ARB_map_buffer_range"
    "GL_ARB_multi_bind"
    "GL_ARB_multi_draw_indirect"
    "GL_ARB_multisample"
    "GL_ARB_multitexture"
    "GL_ARB_occlusion_query"
    "GL_ARB_occlusion_query2"
    "GL_ARB_parallel_shader_compile"
    "GL_ARB_pipeline_statistics_query"
    "GL_ARB_pixel_buffer_object"
    "GL_ARB_point_parameters"
    "GL_ARB_point_sprite"
    "GL_ARB_polygon_offset_clamp"
    "GL_ARB_post_depth_coverage"
    "GL_ARB_program_interface_query"
    "GL_ARB_provoking_vertex"
    "GL_ARB_query_buffer_object"
    "GL_ARB_robust_buffer_access_behavior"
    "GL_ARB_robustness"
    "GL_ARB_sample_shading"
    "GL_ARB_sampler_objects"
    "GL_ARB_seamless_cube_map"
    "GL_ARB_seamless_cubemap_per_texture"
    "GL_ARB_separate_shader_objects"
    "GL_ARB_shader_atomic_counter_ops"
    "GL_ARB_shader_atomic_counters"
    "GL_ARB_shader_ballot"
    "GL_ARB_shader_bit_encoding"
    "GL_ARB_shader_clock"
    "GL_ARB_shader_draw_parameters"
    "GL_ARB_shader_group_vote"
    "GL_ARB_shader_image_load_store"
    "GL_ARB_shader_image_size"
    "GL_ARB_shader_precision"
    "GL_ARB_shader_storage_buffer_object"
    "GL_ARB_shader_subroutine"
    "GL_ARB_shader_texture_image_samples"
    "GL_ARB_shader_texture_lod"
    "GL_ARB_shader_viewport_layer_array"
    "GL_ARB_shading_language_100"
    "GL_ARB_shading_language_420pack"
    "GL_ARB_shading_language_include"
    "GL_ARB_shading_language_packing"
    "GL_ARB_shadow"
    "GL_ARB_spirv_extensions"
    "GL_ARB_stencil_texturing"
    "GL_ARB_sync"
    "GL_ARB_tessellation_shader"
    "GL_ARB_texture_barrier"
    "GL_ARB_texture_border_clamp"
    "GL_ARB_texture_buffer_object"
    "GL_ARB_texture_buffer_object_rgb32"
    "GL_ARB_texture_buffer_range"
    "GL_ARB_texture_compression"
    "GL_ARB_texture_compression_bptc"
    "GL_ARB_texture_compression_rgtc"
    "GL_ARB_texture_cube_map"
    "GL_ARB_texture_cube_map_array"
    "GL_ARB_texture_filter_anisotropic"
    "GL_ARB_texture_float"
    "GL_ARB_texture_gather"
    "GL_ARB_texture_mirror_clamp_to_edge"
    "GL_ARB_texture_mirrored_repeat"
    "GL_ARB_texture_multisample"
    "GL_ARB_texture_non_power_of_two"
    "GL_ARB_texture_query_levels"
    "GL_ARB_texture_query_lod"
    "GL_ARB_texture_rectangle"
    "GL_ARB_texture_rg"
    "GL_ARB_texture_rgb10_a2ui"
    "GL_ARB_texture_stencil8"
    "GL_ARB_texture_storage"
    "GL_ARB_texture_storage_multisample"
    "GL_ARB_texture_swizzle"
    "GL_ARB_texture_view"
    "GL_ARB_timer_query"
    "GL_ARB_transform_feedback2"
    "GL_ARB_transform_feedback3"
    "GL_ARB_transform_feedback_instanced"
    "GL_ARB_transform_feedback_overflow_query"
    "GL_ARB_uniform_buffer_object"
    "GL_ARB_vertex_array_bgra"
    "GL_ARB_vertex_array_object"
    "GL_ARB_vertex_attrib_64bit"
    "GL_ARB_vertex_attrib_binding"
    "GL_ARB_vertex_buffer_object"
    "GL_ARB_vertex_program"
    "GL_ARB_vertex_type_10f_11f_11f_rev"
    "GL_ARB_vertex_type_2_10_10_10_rev"
    "GL_ARB_viewport_array"
    "GL_EXT_bgra"
    "GL_EXT_blend_color"
    "GL_EXT_blend_equation_separate"
    "GL_EXT_blend_func_separate"
    "GL_EXT_blend_minmax"
    "GL_EXT_blend_subtract"
    "GL_EXT_depth_bounds_test"
    "GL_EXT_direct_state_access"
    "GL_EXT_draw_buffers2"
    "GL_EXT_draw_instanced"
    "GL_EXT_draw_range_elements"
    "GL_EXT_framebuffer_blit"
    "GL_EXT_framebuffer_multisample"
    "GL_EXT_framebuffer_multisample_blit_scaled"
    "GL_EXT_framebuffer_object"
    "GL_EXT_framebuffer_sRGB"
    "GL_EXT_gpu_shader4"
    "GL_EXT_memory_object"
    "GL_EXT_memory_object_win32"
    "GL_EXT_multi_draw_arrays"
    "GL_EXT_packed_depth_stencil"
    "GL_EXT_packed_float"
    "GL_EXT_pixel_buffer_object"
    "GL_EXT_point_parameters"
    "GL_EXT_polygon_offset_clamp"
    "GL_EXT_post_depth_coverage"
    "GL_EXT_provoking_vertex"
    "GL_EXT_raster_multisample"
    "GL_EXT_semaphore"
    "GL_EXT_semaphore_win32"
    "GL_EXT_shader_image_load_formatted"
    "GL_EXT_shader_image_load_store"
    "GL_EXT_shader_integer_mix"
    "GL_EXT_shadow_funcs"
    "GL_EXT_stencil_wrap"
    "GL_EXT_texture3D"
    "GL_EXT_texture_array"
    "GL_EXT_texture_buffer_object"
    "GL_EXT_texture_compression_dxt1"
    "GL_EXT_texture_compression_rgtc"
    "GL_EXT_texture_compression_s3tc"
    "GL_EXT_texture_cube_map"
    "GL_EXT_texture_edge_clamp"
    "GL_EXT_texture_filter_anisotropic"
    "GL_EXT_texture_filter_minmax"
    "GL_EXT_texture_integer"
    "GL_EXT_texture_lod_bias"
    "GL_EXT_texture_mirror_clamp"
    "GL_EXT_texture_sRGB"
    "GL_EXT_texture_sRGB_decode"
    "GL_EXT_texture_shared_exponent"
    "GL_EXT_texture_swizzle"
    "GL_EXT_timer_query"
    "GL_EXT_vertex_attrib_64bit"
    "GL_EXT_win32_keyed_mutex"
    "GL_KHR_blend_equation_advanced"
    "GL_KHR_blend_equation_advanced_coherent"
    "GL_KHR_context_flush_control"
    "GL_KHR_debug"
    "GL_KHR_no_error"
    "GL_KHR_parallel_shader_compile"
    "GL_KHR_robust_buffer_access_behavior"
    "GL_KHR_robustness"
    "WGL_EXT_swap_control"
    "GL_EXT_debug_tool"
    "GL_GREMEDY_frame_terminator"
    "GL_GREMEDY_string_marker"
2

Only if the driver implements that extension. If it doesn’t provide the glTextureBarrierNV function, it shouldn’t report the extension.

An implementation isn’t required to implement any extensions. If an extension is incorporated into core without any changes, then an implementation can “support” it by simply reporting it in the extension list (but there’s no requirement to do so). But for non-ARB extensions, the driver would at a minimum have to provide the alternate function names. And if the core implementation differs from the extension in any way, implementing the extension requires implementing both versions; you can’t just consider the version that was incorporated into core to be “close enough”.

Also, claiming support for another vendor’s extensions isn’t without risk. If the original specification doesn’t quite match the vendor’s implementation, expect the specification to change rather than the implementation.

3

Are you using it correctly? That is, are you querying the number of extensions correctly?

Show us the code you use to enumerate extensions.

4

Sure–it’d be strange for it to work for some extensions but not all, but OpenGL never fails to surprise me:

    GLint numExtensions = 0;
    context->getIntegerv(GL_NUM_EXTENSIONS, &numExtensions);
    Extensions.reserve(numExtensions);
    for (GLint e = 0; e < numExtensions; ++e)
    {
        Extensions.emplace_back(reinterpret_cast<const char*>(context->getStringi(GL_EXTENSIONS, e)));
    }

Using that code, we’ve also received analytics/bug reports from Nvidia users that do include vendor-specific extensions, including GL_NV_texture_barrier, so this has the smell of driver-specific behaviour.

5

The NVidia driver is reporting a full extension list here. What do you get for these strings:

glGetString( GL_RENDERER )
glGetString( GL_VERSION )
glGetString( GL_EXTENSIONS )

Looking at your extension list, and comparing with an extension list emitted here on the nearly same GPU (GTX 1080Ti, instead of 1080 non-Ti) by a recent NV driver (430.39) on Windows in a compatibility context (when running the GL app directly)…

  • I see these extensions in your list that are not in the list emitted by this NV driver here:
GL_EXT_debug_tool
GL_GREMEDY_frame_terminator
GL_GREMEDY_string_marker
  • and I see these extensions in this NV driver’s extension list that are omitted from yours:
GL_AMD_multi_draw_indirect
GL_AMD_seamless_cubemap_per_texture
GL_AMD_vertex_shader_layer
GL_AMD_vertex_shader_viewport_index
GL_ARB_ES3_2_compatibility
GL_ARB_bindless_texture
GL_ARB_compatibility
GL_ARB_fragment_program
GL_ARB_fragment_program_shadow
GL_ARB_fragment_shader
GL_ARB_gpu_shader_int64
GL_ARB_imaging
GL_ARB_sample_locations
GL_ARB_shader_objects
GL_ARB_sparse_buffer
GL_ARB_sparse_texture
GL_ARB_sparse_texture2
GL_ARB_sparse_texture_clamp
GL_ARB_texture_env_add
GL_ARB_texture_env_combine
GL_ARB_texture_env_crossbar
GL_ARB_texture_env_dot3
GL_ARB_texture_filter_minmax
GL_ARB_transpose_matrix
GL_ARB_vertex_shader
GL_ARB_window_pos
GL_ATI_draw_buffers
GL_ATI_texture_float
GL_ATI_texture_mirror_once
GL_EXTX_framebuffer_mixed_formats
GL_EXT_Cg_shader
GL_EXT_abgr
GL_EXT_bindable_uniform
GL_EXT_compiled_vertex_array
GL_EXT_fog_coord
GL_EXT_geometry_shader4
GL_EXT_gpu_program_parameters
GL_EXT_import_sync_object
GL_EXT_packed_pixels
GL_EXT_rescale_normal
GL_EXT_secondary_color
GL_EXT_separate_shader_objects
GL_EXT_separate_specular_color
GL_EXT_sparse_texture2
GL_EXT_stencil_two_side
GL_EXT_texture_compression_latc
GL_EXT_texture_env_add
GL_EXT_texture_env_combine
GL_EXT_texture_env_dot3
GL_EXT_texture_lod
GL_EXT_texture_object
GL_EXT_texture_sRGB_R8
GL_EXT_texture_storage
GL_EXT_transform_feedback2
GL_EXT_vertex_array
GL_EXT_vertex_array_bgra
GL_EXT_window_rectangles
GL_IBM_rasterpos_clip
GL_IBM_texture_mirrored_repeat
GL_KTX_buffer_region
GL_NVX_blend_equation_advanced_multi_draw_buffers
GL_NVX_conditional_render
GL_NVX_gpu_memory_info
GL_NVX_multigpu_info
GL_NVX_nvenc_interop
GL_NV_ES1_1_compatibility
GL_NV_ES3_1_compatibility
GL_NV_alpha_to_coverage_dither_control
GL_NV_bindless_multi_draw_indirect
GL_NV_bindless_multi_draw_indirect_count
GL_NV_bindless_texture
GL_NV_blend_equation_advanced
GL_NV_blend_equation_advanced_coherent
GL_NV_blend_minmax_factor
GL_NV_blend_square
GL_NV_clip_space_w_scaling
GL_NV_command_list
GL_NV_compute_program5
GL_NV_conditional_render
GL_NV_conservative_raster
GL_NV_conservative_raster_dilate
GL_NV_conservative_raster_pre_snap_triangles
GL_NV_copy_depth_to_color
GL_NV_copy_image
GL_NV_depth_buffer_float
GL_NV_depth_clamp
GL_NV_draw_texture
GL_NV_draw_vulkan_image
GL_NV_explicit_multisample
GL_NV_feature_query
GL_NV_fence
GL_NV_fill_rectangle
GL_NV_float_buffer
GL_NV_fog_distance
GL_NV_fragment_coverage_to_color
GL_NV_fragment_program
GL_NV_fragment_program2
GL_NV_fragment_program_option
GL_NV_fragment_shader_interlock
GL_NV_framebuffer_mixed_samples
GL_NV_framebuffer_multisample_coverage
GL_NV_geometry_shader4
GL_NV_geometry_shader_passthrough
GL_NV_gpu_program4
GL_NV_gpu_program4_1
GL_NV_gpu_program5
GL_NV_gpu_program5_mem_extended
GL_NV_gpu_program_fp64
GL_NV_gpu_shader5
GL_NV_half_float
GL_NV_internalformat_sample_query
GL_NV_light_max_exponent
GL_NV_memory_attachment
GL_NV_multisample_coverage
GL_NV_multisample_filter_hint
GL_NV_occlusion_query
GL_NV_packed_depth_stencil
GL_NV_parameter_buffer_object
GL_NV_parameter_buffer_object2
GL_NV_path_rendering
GL_NV_path_rendering_shared_edge
GL_NV_pixel_data_range
GL_NV_point_sprite
GL_NV_primitive_restart
GL_NV_query_resource
GL_NV_query_resource_tag
GL_NV_register_combiners
GL_NV_register_combiners2
GL_NV_sample_locations
GL_NV_sample_mask_override_coverage
GL_NV_shader_atomic_counters
GL_NV_shader_atomic_float
GL_NV_shader_atomic_float64
GL_NV_shader_atomic_fp16_vector
GL_NV_shader_atomic_int64
GL_NV_shader_buffer_load
GL_NV_shader_storage_buffer_object
GL_NV_shader_thread_group
GL_NV_shader_thread_shuffle
GL_NV_stereo_view_rendering
GL_NV_texgen_reflection
GL_NV_texture_barrier
GL_NV_texture_compression_vtc
GL_NV_texture_env_combine4
GL_NV_texture_multisample
GL_NV_texture_rectangle
GL_NV_texture_rectangle_compressed
GL_NV_texture_shader
GL_NV_texture_shader2
GL_NV_texture_shader3
GL_NV_transform_feedback
GL_NV_transform_feedback2
GL_NV_uniform_buffer_unified_memory
GL_NV_vertex_array_range
GL_NV_vertex_array_range2
GL_NV_vertex_attrib_integer_64bit
GL_NV_vertex_buffer_unified_memory
GL_NV_vertex_program
GL_NV_vertex_program1_1
GL_NV_vertex_program2
GL_NV_vertex_program2_option
GL_NV_vertex_program3
GL_NV_viewport_array2
GL_NV_viewport_swizzle
GL_OVR_multiview
GL_OVR_multiview2
GL_S3_s3tc
GL_SGIS_generate_mipmap
GL_SGIS_texture_lod
GL_SGIX_depth_texture
GL_SGIX_shadow
GL_SUN_slice_accum
GL_WIN_swap_hint

These results suggests several questions:

  1. Are you capturing this list while running your app under some GL call trace-based capture or profiling tool?
    (…such as Nsight Graphics, apitrace, or CodeXL. The extensions added in your list suggest this question. They’re obviously being appended to the list, and this makes them the only ones out of sorted order.)
  2. What kind of context are you using to query extensions?
    (GL_ARB_compatibility is missing from your list, so it’s probably a core or core+forward-compatible context)
  3. What code in your app is sorting the extension list?
    (The order the extensions are emitted by the NV driver here is not alphabetical order. The same code that’s doing the sorting could be doing the filtering too…)
6

Are you capturing this list while running your app under some GL call trace-based capture or profiling tool ?

I think you might be onto something there! I actually run with RenderDoc injected more often than not, and considering it only works with Core contexts, it’s likely enforcing that subset of functionality by restricting the extensions being exposed. Doh!

What kind of context are you using to query extensions?

Core. Even though I also tested with a Compatibility profile, I still had RenderDoc active when I did, which could explain why the result was the same.

What code in your app is sorting the extension list?

Probably RenderDoc again…

I’ll try confirm once I get back on the same machine, but that’s almost certainly it. :woman_facepalming: