Fix duplicate symbols in plugin DLL.

PiperOrigin-RevId: 491340247
Change-Id: If559d60371ad604b94b92efd01ed6de9ecf6f2b0

plugin/elasticity/CMakeLists.txt

@@ -20,6 +20,7 @@ set(MUJOCO_ELASTICITY_INCLUDE
 set(MUJOCO_ELASTICITY_SRCS
     cable.cc
     cable.h
+    elasticity.cc
     solid.cc
     solid.h
 )

plugin/elasticity/cable.cc

@@ -221,7 +221,7 @@ void Cable::Compute(const mjModel* m, mjData* d, int instance) {
 
 
 
-mjPLUGIN_DYNAMIC_LIBRARY_INIT {
+void Cable::RegisterPlugin() {
   mjpPlugin plugin;
   mjp_defaultPlugin(&plugin);
 

plugin/elasticity/cable.h

@@ -36,6 +36,8 @@ class Cable {
 
   void Compute(const mjModel* m, mjData* d, int instance);
 
+  static void RegisterPlugin();
+
   int i0;                         // index of first body
   int n;                          // number of bodies in the cable
   std::vector<int> prev;          // indices of previous bodies   (n x 1)

plugin/elasticity/elasticity.cc

@@ -0,0 +1,26 @@
+// Copyright 2022 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <mujoco/mjplugin.h>
+#include "cable.h"
+#include "solid.h"
+
+namespace mujoco::plugin::elasticity {
+
+mjPLUGIN_DYNAMIC_LIBRARY_INIT {
+  Cable::RegisterPlugin();
+  Solid::RegisterPlugin();
+}
+
+}  // namespace mujoco::plugin::elasticity

plugin/elasticity/solid.cc

@@ -342,7 +342,7 @@ void Solid::Compute(const mjModel* m, mjData* d, int instance) {
 
 
 
-mjPLUGIN_DYNAMIC_LIBRARY_INIT {
+void Solid::RegisterPlugin() {
   mjpPlugin plugin;
   mjp_defaultPlugin(&plugin);
 

plugin/elasticity/solid.h

@@ -41,6 +41,8 @@ class Solid {
 
   void Compute(const mjModel* m, mjData* d, int instance);
 
+  static void RegisterPlugin();
+
   int i0;  // index of first body
   int nc;  // number of cubes in the grid
   int nv;  // number of vertices (bodies) in the solid