Segfault when reading gltf using EXT_meshopt_compression / ...

[paulmelis]

Description

This is with a .glb as output by gltfpack, which uses a few extensions:

melis@blackbox 12:56:~/c/StereoKit-develop$ ~/concepts/glbdump/glbdump model.glb
Total file size 2,189,208 bytes

JSON chunk (22,640 bytes)

Asset Version   : 2.0
      Generator : "gltfpack 0.20"

Extensions (used)     : KHR_mesh_quantization, EXT_meshopt_compression, KHR_texture_transform
           (required) : KHR_mesh_quantization, EXT_meshopt_compression

It's okay if SK refuses to read anything that it can't handle in terms of glTF extensions, but since I'm getting a segfault (below) I assume there's something wrong in the decoding of (probably) the EXT_meshopt_compression data. Or perhaps the quantization used. Interestingly, cgltf does not list support for KHR_mesh_quantization in its readme, but does appear to actually support it.

Edit: just tested with a file using only KHR_mesh_quantization and KHR_texture_transform (same input file, no -c option to gltfpack) and that loads without problems.

Platform / Environment

Linux, SK repo (ea5e48d)

Logs or exception details

#include <stdio.h>
#include "stereokit.h"

using namespace sk;

int main()
{
    sk_settings_t settings = {};
    settings.app_name      = "StereoKit C";
    settings.assets_folder = "Assets";
    settings.mode          = app_mode_xr;

    if (!sk_init(settings))
	return 1;    
    
    model_t m = model_create_file("model.glb");
    
    sk_shutdown();
}

Appears to be a null pointer:

[SK diagnostic] Initializing World
[SK diagnostic] Initializing Physics
[SK diagnostic] Initializing Input
[SK info] Initialization successful

Thread 1 "StereoKit Main" received signal SIGSEGV, Segmentation fault.
0x00007ffff7e42fc0 in sk::gltf_parsemesh (mesh=<optimized out>, warnings=<optimized out>, filename=<optimized out>, primitive_id=<optimized out>, node_id=<optimized out>)
    at /home/melis/c/StereoKit-develop/StereoKitC/asset_types/model_gltf.cpp:406
406					inds[v] = *ind;
(gdb) p v
$1 = <optimized out>
(gdb) p ind
$2 = (uint16_t *) 0x0

model.glb.gz

[maluoi]

Ay okay, that's not great, yeah! I can definitely reproduce that with your model.

I do have some work related to this in the feature/gltf_meshopt branch. I believe I had a number of models from gltfpack working, but it looks like it doesn't work on yours. Doesn't crash, but doesn't load it right yet.