Cleanup: avoid error prone struct declarations in C++

Reference struct members by name instead relying on their order.
This also simplifies moving back to named members when all compilers
we use support them.

source/blender/blenkernel/intern/mesh.cc

@@ -1138,8 +1138,12 @@ BMesh *BKE_mesh_to_bmesh(Mesh *me,
                          const bool add_key_index,
                          const struct BMeshCreateParams *params)
 {
-  struct BMeshFromMeshParams bmfmp = {false, add_key_index, true, ob->shapenr};
-  return BKE_mesh_to_bmesh_ex(me, params, &bmfmp);
+  BMeshFromMeshParams bmesh_from_mesh_params{};
+  bmesh_from_mesh_params.calc_face_normal = false;
+  bmesh_from_mesh_params.add_key_index = add_key_index;
+  bmesh_from_mesh_params.use_shapekey = true;
+  bmesh_from_mesh_params.active_shapekey = ob->shapenr;
+  return BKE_mesh_to_bmesh_ex(me, params, &bmesh_from_mesh_params);
 }
 
 Mesh *BKE_mesh_from_bmesh_nomain(BMesh *bm,

source/blender/blenkernel/intern/mesh_remesh_voxel.cc

@@ -410,7 +410,8 @@ struct Mesh *BKE_mesh_remesh_voxel_fix_poles(const Mesh *mesh)
 {
   const BMAllocTemplate allocsize = BMALLOC_TEMPLATE_FROM_ME(mesh);
 
-  const BMeshCreateParams bmesh_create_params = {true};
+  BMeshCreateParams bmesh_create_params{};
+  bmesh_create_params.use_toolflags = true;
   BMesh *bm = BM_mesh_create(&allocsize, &bmesh_create_params);
 
   BMeshFromMeshParams bmesh_from_mesh_params{};

source/blender/bmesh/tests/bmesh_core_test.cc

@@ -10,9 +10,9 @@ TEST(bmesh_core, BMVertCreate)
   BMVert *bv1, *bv2, *bv3;
   const float co1[3] = {1.0f, 2.0f, 0.0f};
 
-  BMeshCreateParams bm_params;
-  bm_params.use_toolflags = true;
-  bm = BM_mesh_create(&bm_mesh_allocsize_default, &bm_params);
+  BMeshCreateParams bmesh_create_params{};
+  bmesh_create_params.use_toolflags = true;
+  bm = BM_mesh_create(&bm_mesh_allocsize_default, &bmesh_create_params);
   EXPECT_EQ(bm->totvert, 0);
   /* make a custom layer so we can see if it is copied properly */
   BM_data_layer_add(bm, &bm->vdata, CD_PROP_FLOAT);

source/blender/io/alembic/exporter/abc_writer_mesh.cc

@@ -166,9 +166,10 @@ void ABCGenericMeshWriter::do_write(HierarchyContext &context)
     const int quad_method = args_.export_params->quad_method;
     const int ngon_method = args_.export_params->ngon_method;
 
-    struct BMeshCreateParams bmcp = {false};
-    struct BMeshFromMeshParams bmfmp = {true, false, false, 0};
-    BMesh *bm = BKE_mesh_to_bmesh_ex(mesh, &bmcp, &bmfmp);
+    BMeshCreateParams bmesh_create_params{};
+    BMeshFromMeshParams bmesh_from_mesh_params{};
+    bmesh_from_mesh_params.calc_face_normal = true;
+    BMesh *bm = BKE_mesh_to_bmesh_ex(mesh, &bmesh_create_params, &bmesh_from_mesh_params);
 
     BM_mesh_triangulate(bm, quad_method, ngon_method, 4, tag_only, nullptr, nullptr, nullptr);
 

source/blender/io/collada/collada_utils.cpp

@@ -444,14 +444,14 @@ void bc_triangulate_mesh(Mesh *me)
   /* XXX: The triangulation method selection could be offered in the UI. */
   int quad_method = MOD_TRIANGULATE_QUAD_SHORTEDGE;
 
-  const struct BMeshCreateParams bm_create_params = {0};
+  const BMeshCreateParams bm_create_params{};
   BMesh *bm = BM_mesh_create(&bm_mesh_allocsize_default, &bm_create_params);
-  BMeshFromMeshParams bm_from_me_params = {0};
+  BMeshFromMeshParams bm_from_me_params{};
   bm_from_me_params.calc_face_normal = true;
   BM_mesh_bm_from_me(bm, me, &bm_from_me_params);
   BM_mesh_triangulate(bm, quad_method, use_beauty, 4, tag_only, nullptr, nullptr, nullptr);
 
-  BMeshToMeshParams bm_to_me_params = {0};
+  BMeshToMeshParams bm_to_me_params{};
   bm_to_me_params.calc_object_remap = false;
   BM_mesh_bm_to_me(nullptr, bm, me, &bm_to_me_params);
   BM_mesh_free(bm);

source/blender/modifiers/intern/MOD_boolean.cc

@@ -245,12 +245,12 @@ static BMesh *BMD_mesh_bm_create(
 
   const BMAllocTemplate allocsize = BMALLOC_TEMPLATE_FROM_ME(mesh, mesh_operand_ob);
 
-  BMeshCreateParams bmcp = {false};
-  BMesh *bm = BM_mesh_create(&allocsize, &bmcp);
+  BMeshCreateParams bmesh_create_params{};
+  BMesh *bm = BM_mesh_create(&allocsize, &bmesh_create_params);
 
-  BMeshFromMeshParams params{};
-  params.calc_face_normal = true;
-  BM_mesh_bm_from_me(bm, mesh_operand_ob, &params);
+  BMeshFromMeshParams bmesh_from_mesh_params{};
+  bmesh_from_mesh_params.calc_face_normal = true;
+  BM_mesh_bm_from_me(bm, mesh_operand_ob, &bmesh_from_mesh_params);
 
   if (UNLIKELY(*r_is_flip)) {
     const int cd_loop_mdisp_offset = CustomData_get_offset(&bm->ldata, CD_MDISPS);
@@ -261,7 +261,7 @@ static BMesh *BMD_mesh_bm_create(
     }
   }
 
-  BM_mesh_bm_from_me(bm, mesh, &params);
+  BM_mesh_bm_from_me(bm, mesh, &bmesh_from_mesh_params);
 
   return bm;
 }
@@ -535,9 +535,9 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
           BMD_mesh_intersection(bm, md, ctx, mesh_operand_ob, object, operand_ob, is_flip);
 
           /* Needed for multiple objects to work. */
-          BMeshToMeshParams params{};
-          params.calc_object_remap = false;
-          BM_mesh_bm_to_me(nullptr, bm, mesh, &params);
+          BMeshToMeshParams bmesh_to_mesh_params{};
+          bmesh_to_mesh_params.calc_object_remap = false;
+          BM_mesh_bm_to_me(nullptr, bm, mesh, &bmesh_to_mesh_params);
 
           result = BKE_mesh_from_bmesh_for_eval_nomain(bm, nullptr, mesh);
           BM_mesh_free(bm);

source/blender/nodes/geometry/nodes/node_geo_edge_split.cc

@@ -33,12 +33,13 @@ static void geo_node_edge_split_declare(NodeDeclarationBuilder &b)
 
 static Mesh *mesh_edge_split(const Mesh &mesh, const IndexMask selection)
 {
-  const BMeshCreateParams bmcp = {true};
+  BMeshCreateParams bmesh_create_params{};
+  bmesh_create_params.use_toolflags = true;
   const BMAllocTemplate allocsize = {0, 0, 0, 0};
-  BMesh *bm = BM_mesh_create(&allocsize, &bmcp);
+  BMesh *bm = BM_mesh_create(&allocsize, &bmesh_create_params);
 
-  BMeshFromMeshParams params{};
-  BM_mesh_bm_from_me(bm, &mesh, &params);
+  BMeshFromMeshParams bmesh_from_mesh_params{};
+  BM_mesh_bm_from_me(bm, &mesh, &bmesh_from_mesh_params);
 
   BM_mesh_elem_table_ensure(bm, BM_EDGE);
   for (const int i : selection) {

source/blender/nodes/geometry/nodes/node_geo_mesh_primitive_ico_sphere.cc

@@ -45,9 +45,10 @@ static Mesh *create_ico_sphere_mesh(const int subdivisions, const float radius)
 {
   const float4x4 transform = float4x4::identity();
 
-  const BMeshCreateParams bmcp = {true};
+  BMeshCreateParams bmesh_create_params{};
+  bmesh_create_params.use_toolflags = true;
   const BMAllocTemplate allocsize = {0, 0, 0, 0};
-  BMesh *bm = BM_mesh_create(&allocsize, &bmcp);
+  BMesh *bm = BM_mesh_create(&allocsize, &bmesh_create_params);
   BM_data_layer_add_named(bm, &bm->ldata, CD_MLOOPUV, nullptr);
 
   BMO_op_callf(bm,