Fix T56108: Crash editing corrupted vertex groups

While the file in this report had corrupted values,
this is avoidable without adding any extra overhead.

Use unsigned vertex group indices since we don't need negative values,
this is an alternative to checking they aren't negative in many places.

Vertex group values over INT_MAX is still considered invalid,
so any accidental unsigned wrapping won't be silently ignored.

1 files changed, 6 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/mesh_validate.c b/source/blender/blenkernel/intern/mesh_validate.c
index 4aa5bfa04ab..e4de75b923f 100644
--- a/source/blender/blenkernel/intern/mesh_validate.c
+++ b/source/blender/blenkernel/intern/mesh_validate.c
@@ -784,22 +784,24 @@ bool BKE_mesh_validate_arrays(Mesh *mesh,
       for (j = 0, dw = dv->dw; j < dv->totweight; j++, dw++) {
         /* note, greater than max defgroups is accounted for in our code, but not < 0 */
         if (!isfinite(dw->weight)) {
-          PRINT_ERR("\tVertex deform %u, group %d has weight: %f", i, dw->def_nr, dw->weight);
+          PRINT_ERR("\tVertex deform %u, group %u has weight: %f", i, dw->def_nr, dw->weight);
           if (do_fixes) {
             dw->weight = 0.0f;
             fix_flag.verts_weight = true;
           }
         }
         else if (dw->weight < 0.0f || dw->weight > 1.0f) {
-          PRINT_ERR("\tVertex deform %u, group %d has weight: %f", i, dw->def_nr, dw->weight);
+          PRINT_ERR("\tVertex deform %u, group %u has weight: %f", i, dw->def_nr, dw->weight);
           if (do_fixes) {
             CLAMP(dw->weight, 0.0f, 1.0f);
             fix_flag.verts_weight = true;
           }
         }
 
-        if (dw->def_nr < 0) {
-          PRINT_ERR("\tVertex deform %u, has invalid group %d", i, dw->def_nr);
+        /* Not technically incorrect since this is unsigned, however,
+         * a value over INT_MAX is almost certainly caused by wrapping an unsigned int. */
+        if (dw->def_nr >= INT_MAX) {
+          PRINT_ERR("\tVertex deform %u, has invalid group %u", i, dw->def_nr);
           if (do_fixes) {
             defvert_remove_group(dv, dw);
             fix_flag.verts_weight = true;