Modify mj_PLUGIN_LIB_INIT to support multiple plugins in the same compilation unit.

Previously on MSVC we used DllMain to register plugins, you cannot have multiple definitions of DllMain in a single unit so you would get errors if you tried to register two plugins. This modifies the implementation to insert a function pointer into the C runtime initialization instead.

PiperOrigin-RevId: 896612678
Change-Id: I07732147b955d741c836acff6da986db0e9b9eff

plugin/actuator/register.cc

@@ -17,6 +17,6 @@
 
 namespace mujoco::plugin::actuator {
 
-mjPLUGIN_LIB_INIT { Pid::RegisterPlugin(); }
+mjPLUGIN_LIB_INIT(actuator) { Pid::RegisterPlugin(); }
 
 }  // namespace mujoco::plugin::actuator

plugin/elasticity/register.cc

@@ -17,7 +17,7 @@
 
 namespace mujoco::plugin::elasticity {
 
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(elasticity) {
   Cable::RegisterPlugin();
 }
 

plugin/obj_decoder/obj_decoder.cc

@@ -114,7 +114,7 @@ int CanDecode(const mjResource* resource) {
 
 }  // namespace
 
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(obj_decoder) {
   mjpDecoder decoder;
   mjp_defaultDecoder(&decoder);
   decoder.content_type = "model/obj";

plugin/sdf/register.cc

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <mujoco/mjplugin.h>
 #include "bolt.h"
 #include "bowl.h"
 #include "gear.h"
@@ -20,7 +21,7 @@
 
 namespace mujoco::plugin::sdf {
 
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(sdf) {
   Bolt::RegisterPlugin();
   Bowl::RegisterPlugin();
   Gear::RegisterPlugin();

plugin/sensor/register.cc

@@ -17,7 +17,7 @@
 
 namespace mujoco::plugin::sensor {
 
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(sensor) {
   TouchGrid::RegisterPlugin();
 }
 

plugin/stl_decoder/stl_decoder.cc

@@ -132,7 +132,7 @@ int CanDecode(const mjResource* resource) {
 
 }  // namespace
 
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(stl_decoder) {
   mjpDecoder decoder;
   mjp_defaultDecoder(&decoder);
   decoder.content_type = "model/stl";

plugin/usd_decoder/usd_decoder.cc

@@ -2459,7 +2459,7 @@ int CanDecode(const mjResource* resource) {
 }  // namespace
 
 // clang-format off
-mjPLUGIN_LIB_INIT {
+mjPLUGIN_LIB_INIT(usd_decoder) {
   mjpDecoder decoder;
   mjp_defaultDecoder(&decoder);
   decoder.content_type = "model/usd";