MeshDataTool crash when changing vertex data.

[Gyrth]

Godot version:
Godot_v3.3.1-stable_x11.64

OS/device including version:
Manjaro Linux x86_64
Intel i5-6600K (4) @ 3.900GHz
NVIDIA GeForce GTX 1060 6GB 460.80

Issue description:
When using DataMeshTool to change vertex bones, vertex weights and possibly other attributes it crashes when using commit_to_surface. I've set these values to empty PoolArrays in the reproduction project, but from my testing it also crashes when using valid data.

Steps to reproduce:

• Run test project.
• Crash.

Backtrace

ERROR: get: FATAL: Index p_index = 1 is out of bounds (size() = 1).
   At: ./core/cowdata.h:156.
handle_crash: Program crashed with signal 4
Dumping the backtrace. Please include this when reporting the bug on https://github.com/godotengine/godot/issues
[1] /usr/lib/libc.so.6(+0x3cf80) [0x7f15c0e1df80] (??:0)
[2] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x15de6ed] (??:0)
[3] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x15c899f] (??:0)
[4] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0xe3a2b6] (??:0)
[5] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0xd72289] (??:0)
[6] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x2ff2c44] (??:?)
[7] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x302cab5] (??:?)
[8] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1ceae15] (??:0)
[9] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x19ef8c8] (??:0)
[10] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0xdfdbb4] (??:0)
[11] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1cae92a] (??:0)
[12] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1cae880] (??:0)
[13] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1cae880] (??:0)
[14] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1ce8ea7] (??:0)
[15] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x1ce922f] (??:0)
[16] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x98e396] (??:0)
[17] /usr/lib/libc.so.6(__libc_start_main+0xd5) [0x7f15c0e08b25] (??:0)
[18] /home/gyrth/Documents/Godot_v3.3.1-stable_x11.64() [0x99cb9e] (??:0)
-- END OF BACKTRACE --

Minimal reproduction project:
BugReport.zip

[akien-mga]

Confirmed in 3.x and master. Backtrace for latest master (65eff1c):

Thread 1 "godot-git" received signal SIGILL, Illegal instruction.
0x00000000022afc29 in CowData<float>::get (this=0xb3379b0, p_index=0) at ./core/templates/cowdata.h:157
157                     CRASH_BAD_INDEX(p_index, size());
(gdb) bt
#0  0x00000000022afc29 in CowData<float>::get (this=0xb3379b0, p_index=0) at ./core/templates/cowdata.h:157
#1  0x000000000229b46a in Vector<float>::operator[] (this=0xb3379a8, p_index=0) at ./core/templates/vector.h:89
#2  0x0000000004cd03f1 in MeshDataTool::commit_to_surface (this=0xb1711e0, p_mesh=...) at scene/resources/mesh_data_tool.cpp:280
#3  0x0000000004cdcbf5 in call_with_variant_args_ret_helper<__UnexistingClass, Error, Ref<ArrayMesh> const&, 0ul> (p_instance=0xb1711e0, p_method=
    (Error (__UnexistingClass::*)(__UnexistingClass * const, const Ref<ArrayMesh> &)) 0x4ccfede <MeshDataTool::commit_to_surface(Ref<ArrayMesh> const&)>, p_args=0x7fffffff8ee8, r_ret=..., r_error=...)
    at ./core/variant/binder_common.h:635
#4  0x0000000004cdc023 in call_with_variant_args_ret_dv<__UnexistingClass, Error, Ref<ArrayMesh> const&> (p_instance=0xb1711e0, p_method=
    (Error (__UnexistingClass::*)(__UnexistingClass * const, const Ref<ArrayMesh> &)) 0x4ccfede <MeshDataTool::commit_to_surface(Ref<ArrayMesh> const&)>, p_args=0x7fffffff9310, p_argcount=1, r_ret=..., 
    r_error=..., default_values=...) at ./core/variant/binder_common.h:440
#5  0x0000000004cdb3f8 in MethodBindTR<Error, Ref<ArrayMesh> const&>::call (this=0xabd61b0, p_object=0xb1711e0, p_args=0x7fffffff9310, p_arg_count=1, r_error=...) at ./core/object/method_bind.h:452
#6  0x0000000005b92d9a in Object::call (this=0xb1711e0, p_method=..., p_args=0x7fffffff9310, p_argcount=1, r_error=...) at core/object/object.cpp:784
#7  0x0000000005969008 in Variant::call (this=0x7fffffff91a8, p_method=..., p_args=0x7fffffff9310, p_argcount=1, r_ret=..., r_error=...) at core/variant/variant_call.cpp:978
#8  0x000000000308b0d3 in GDScriptFunction::call (this=0xb1ff210, p_instance=0xb174b50, p_args=0x7fffffffca90, p_argcount=0, r_err=..., p_state=0x0) at modules/gdscript/gdscript_vm.cpp:1471
#9  0x0000000002f9febb in GDScriptInstance::call (this=0xb174b50, p_method=..., p_args=0x7fffffffca90, p_argcount=0, r_error=...) at modules/gdscript/gdscript.cpp:1556
#10 0x0000000005baa7c4 in ScriptInstance::call (this=0xb174b50, p_method=..., p_arg1=..., p_arg2=..., p_arg3=..., p_arg4=..., p_arg5=...) at core/object/script_language.cpp:322
#11 0x000000000445f789 in Node::_notification (this=0xb1b6250, p_notification=13) at scene/main/node.cpp:147
#12 0x0000000002286e6c in Node::_notificationv (this=0xb1b6250, p_notification=13, p_reversed=false) at ./scene/main/node.h:45
#13 0x000000000228749b in Node3D::_notificationv (this=0xb1b6250, p_notification=13, p_reversed=false) at ./scene/3d/node_3d.h:52
#14 0x00000000034bb909 in VisualInstance3D::_notificationv (this=0xb1b6250, p_notification=13, p_reversed=false) at ./scene/3d/visual_instance_3d.h:40
#15 0x00000000034bc0a1 in GeometryInstance3D::_notificationv (this=0xb1b6250, p_notification=13, p_reversed=false) at ./scene/3d/visual_instance_3d.h:83
#16 0x00000000048a1443 in MeshInstance3D::_notificationv (this=0xb1b6250, p_notification=13, p_reversed=false) at scene/3d/mesh_instance_3d.h:40
#17 0x0000000005b92eb7 in Object::notification (this=0xb1b6250, p_notification=13, p_reversed=false) at core/object/object.cpp:793
#18 0x000000000445fcc5 in Node::_propagate_ready (this=0xb1b6250) at scene/main/node.cpp:188
--Type <RET> for more, q to quit, c to continue without paging--
#19 0x000000000445fc2f in Node::_propagate_ready (this=0xa42fb00) at scene/main/node.cpp:180
#20 0x000000000445fc2f in Node::_propagate_ready (this=0xb07dc60) at scene/main/node.cpp:180
#21 0x000000000446bfc2 in Node::_set_tree (this=0xb07dc60, p_tree=0xad54970) at scene/main/node.cpp:2522
#22 0x000000000448eb2b in SceneTree::initialize (this=0xad54970) at scene/main/scene_tree.cpp:394
#23 0x00000000020ae726 in OS_LinuxBSD::run (this=0x7fffffffd270) at platform/linuxbsd/os_linuxbsd.cpp:266
#24 0x00000000020ab6fa in main (argc=1, argv=0x7fffffffd788) at platform/linuxbsd/godot_linuxbsd.cpp:58

[YuriSizov]

For the record, it crashes because you are expected to have exactly 4 bones and weights on each vertex, or nothing at all. I'll submit a fix for the crash shortly, but for this to work you would need to pad your arrays to the required size (or avoid setting them if they are empty).