Don't accept NaN geom sizes.

PiperOrigin-RevId: 542209911
Change-Id: I80f9728e8e624d19783370ba5072f39624c1bbe7

src/user/user_objects.cc

@@ -1717,6 +1717,11 @@ void mjCGeom::Compile(void) {
     size[2] = mjMAX(fabs(aabb[2]), fabs(aabb[5]));
   }
 
+  for (double s : size) {
+    if (std::isnan(s)) {
+      throw mjCError(this, "nan size in geom '%s' (id = %d)", name.c_str(), id);
+    }
+  }
   // compute aabb
   ComputeAABB();
 

test/user/user_objects_test.cc

@@ -440,6 +440,27 @@ TEST_F(MjCGeomTest, IgnoreBadGeomOutsideInertiagrouprange) {
   mj_deleteModel(m);
 }
 
+// ------------- test invalid size values --------------------------------------
+
+TEST_F(MjCGeomTest, NanSize) {
+  // even if the caller ignores warnings, models shouldn't compile with NaN
+  // geom sizes
+  mju_user_warning = nullptr;
+  static constexpr char xml[] = R"(
+  <mujoco>
+    <worldbody>
+      <body>
+        <geom type="box" size="1 1 nan" mass="1" />
+      </body>
+    </worldbody>
+  </mujoco>
+  )";
+  std::array<char, 1000> error;
+  mjModel* model = LoadModelFromString(xml, error.data(), error.size());
+  ASSERT_THAT(model, testing::IsNull());
+  ASSERT_THAT(error.data(), HasSubstr("nan"));
+}
+
 // ------------- test height fields --------------------------------------------
 
 using MjCHFieldTest = MujocoTest;