Fix T44138: Crash in DataTransfer modifier when selecting a source with no loops.

Simply check and early return in case we have no source or destination items
(verts/edges/loops/polys) available...

Also, fix an assert in `BKE_mesh_calc_normals_poly()`, when called with no poly.

2 files changed, 38 insertions, 6 deletions

diff --git a/source/blender/blenkernel/intern/data_transfer.c b/source/blender/blenkernel/intern/data_transfer.c
index 8f6d4385b55..da00aecf9c0 100644
--- a/source/blender/blenkernel/intern/data_transfer.c
+++ b/source/blender/blenkernel/intern/data_transfer.c
@@ -1157,12 +1157,20 @@ bool BKE_object_data_transfer_dm(
 			const int num_verts_dst = dm_dst ? dm_dst->getNumVerts(dm_dst) : me_dst->totvert;
 
 			if (!geom_map_init[VDATA]) {
-				if ((map_vert_mode == MREMAP_MODE_TOPOLOGY) && (num_verts_dst != dm_src->getNumVerts(dm_src))) {
+				const int num_verts_src = dm_src->getNumVerts(dm_src);
+
+				if ((map_vert_mode == MREMAP_MODE_TOPOLOGY) && (num_verts_dst != num_verts_src)) {
 					BKE_report(reports, RPT_ERROR,
 					           "Source and destination meshes do not have the same amount of vertices, "
 					           "'Topology' mapping cannot be used in this case");
 					return changed;
 				}
+				if (ELEM(0, num_verts_dst, num_verts_src)) {
+					BKE_report(reports, RPT_ERROR,
+					           "Source or destination meshes do not have any vertices, cannot transfer vertex data");
+					return changed;
+				}
+
 				BKE_mesh_remap_calc_verts_from_dm(
 				        map_vert_mode, space_transform, max_distance, ray_radius,
 				        verts_dst, num_verts_dst, dirty_nors_dst, dm_src, &geom_map[VDATA]);
@@ -1197,12 +1205,20 @@ bool BKE_object_data_transfer_dm(
 			const int num_edges_dst = dm_dst ? dm_dst->getNumEdges(dm_dst) : me_dst->totedge;
 
 			if (!geom_map_init[EDATA]) {
-				if ((map_edge_mode == MREMAP_MODE_TOPOLOGY) && (num_edges_dst != dm_src->getNumEdges(dm_src))) {
+				const int num_edges_src = dm_src->getNumEdges(dm_src);
+
+				if ((map_edge_mode == MREMAP_MODE_TOPOLOGY) && (num_edges_dst != num_edges_src)) {
 					BKE_report(reports, RPT_ERROR,
 					           "Source and destination meshes do not have the same amount of edges, "
 					           "'Topology' mapping cannot be used in this case");
 					return changed;
 				}
+				if (ELEM(0, num_edges_dst, num_edges_src)) {
+					BKE_report(reports, RPT_ERROR,
+					           "Source or destination meshes do not have any edges, cannot transfer edge data");
+					return changed;
+				}
+
 				BKE_mesh_remap_calc_edges_from_dm(
 				        map_edge_mode, space_transform, max_distance, ray_radius,
 				        verts_dst, num_verts_dst, edges_dst, num_edges_dst, dirty_nors_dst,
@@ -1248,12 +1264,20 @@ bool BKE_object_data_transfer_dm(
 			MeshRemapIslandsCalc island_callback = data_transfer_get_loop_islands_generator(cddata_type);
 
 			if (!geom_map_init[LDATA]) {
-				if ((map_loop_mode == MREMAP_MODE_TOPOLOGY) && (num_loops_dst != dm_src->getNumLoops(dm_src))) {
+				const int num_loops_src = dm_src->getNumLoops(dm_src);
+
+				if ((map_loop_mode == MREMAP_MODE_TOPOLOGY) && (num_loops_dst != num_loops_src)) {
 					BKE_report(reports, RPT_ERROR,
 					           "Source and destination meshes do not have the same amount of face corners, "
 					           "'Topology' mapping cannot be used in this case");
 					return changed;
 				}
+				if (ELEM(0, num_loops_dst, num_loops_src)) {
+					BKE_report(reports, RPT_ERROR,
+					           "Source or destination meshes do not have any polygons, cannot transfer loop data");
+					return changed;
+				}
+
 				BKE_mesh_remap_calc_loops_from_dm(
 				        map_loop_mode, space_transform, max_distance, ray_radius,
 				        verts_dst, num_verts_dst, edges_dst, num_edges_dst,
@@ -1298,12 +1322,20 @@ bool BKE_object_data_transfer_dm(
 			CustomData *pdata_dst = dm_dst ? dm_dst->getPolyDataLayout(dm_dst) : &me_dst->pdata;
 
 			if (!geom_map_init[PDATA]) {
-				if ((map_poly_mode == MREMAP_MODE_TOPOLOGY) && (num_polys_dst != dm_src->getNumPolys(dm_src))) {
+				const int num_polys_src = dm_src->getNumPolys(dm_src);
+
+				if ((map_poly_mode == MREMAP_MODE_TOPOLOGY) && (num_polys_dst != num_polys_src)) {
 					BKE_report(reports, RPT_ERROR,
 					           "Source and destination meshes do not have the same amount of faces, "
 					           "'Topology' mapping cannot be used in this case");
 					return changed;
 				}
+				if (ELEM(0, num_polys_dst, num_polys_src)) {
+					BKE_report(reports, RPT_ERROR,
+					           "Source or destination meshes do not have any polygons, cannot transfer poly data");
+					return changed;
+				}
+
 				BKE_mesh_remap_calc_polys_from_dm(
 				        map_poly_mode, space_transform, max_distance, ray_radius,
 				        verts_dst, num_verts_dst, loops_dst, num_loops_dst,
diff --git a/source/blender/blenkernel/intern/mesh_evaluate.c b/source/blender/blenkernel/intern/mesh_evaluate.c
index 6c835a72a40..ceb9b016ff2 100644
--- a/source/blender/blenkernel/intern/mesh_evaluate.c
+++ b/source/blender/blenkernel/intern/mesh_evaluate.c
@@ -226,7 +226,7 @@ void BKE_mesh_calc_normals_poly(MVert *mverts, int numVerts, MLoop *mloop, MPoly
 	MPoly *mp;
 
 	if (only_face_normals) {
-		BLI_assert(pnors != NULL);
+		BLI_assert((pnors != NULL) || (numPolys == 0));
 
 #pragma omp parallel for if (numPolys > BKE_MESH_OMP_LIMIT)
 		for (i = 0; i < numPolys; i++) {
@@ -252,12 +252,12 @@ void BKE_mesh_calc_normals_poly(MVert *mverts, int numVerts, MLoop *mloop, MPoly
 		}
 	}
 
-	/* following Mesh convention; we use vertex coordinate itself for normal in this case */
 	for (i = 0; i < numVerts; i++) {
 		MVert *mv = &mverts[i];
 		float *no = tnorms[i];
 
 		if (UNLIKELY(normalize_v3(no) == 0.0f)) {
+			/* following Mesh convention; we use vertex coordinate itself for normal in this case */
 			normalize_v3_v3(no, mv->co);
 		}