Add stack leak test to WriteReadCompare

PiperOrigin-RevId: 572953669
Change-Id: Id6cad3fc86777d68f218119f67c9dc473bdcfcc8

test/user/testdata/auto_limits.xml

@@ -1,6 +1,7 @@
 <mujoco>
   <compiler autolimits="true" />
   <default>
+    <joint armature="0.1"/>
     <default class="limited_false">
       <joint limited="false"/>
     </default>

test/xml/xml_native_writer_test.cc

@@ -1049,8 +1049,10 @@ mjtNum CompareModel(const mjModel* m1, const mjModel* m2,
 }
 
 TEST_F(PluginTest, WriteReadCompare) {
+  // full precision float printing
   FullFloatPrecision increase_precision;
-  // Loop over all xml files in data
+
+  // loop over all xml files in data
   std::vector<std::string> paths = {GetTestDataFilePath("."),
                                     GetModelPath(".")};
   std::string ext(".xml");
@@ -1101,6 +1103,11 @@ TEST_F(PluginTest, WriteReadCompare) {
           mj_deleteModel(mtemp);
         }
 
+        // check for stack memory leak
+        mj_step(m, d);
+        EXPECT_EQ(d->pstack, 0) << "mjData stack memory leak detected in " <<
+            p.path().string() << '\n';
+
         // delete original structures
         mj_deleteData(d);
         mj_deleteModel(m);