From c8517e63a483622f6b4a193cb530f74c9d828b88 Mon Sep 17 00:00:00 2001
From: Nimrod Gileadi <nimrod@google.com>
Date: Thu, 15 Sep 2022 05:28:18 -0700
Subject: [PATCH] Mark mjCError and mjXError as [[nodiscard]].

This lets the compiler catch the mistake of creating an exception without throwing it.

PiperOrigin-RevId: 474536776
Change-Id: I5bd18258ce6ddd266adb1c852b1ba9e3063cd0b2
---
 src/user/user_objects.h | 2 +-
 src/xml/xml_urdf.cc     | 4 ++--
 src/xml/xml_util.h      | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/user/user_objects.h b/src/user/user_objects.h
index 6407ab64..0b457960 100644
--- a/src/user/user_objects.h
+++ b/src/user/user_objects.h
@@ -84,7 +84,7 @@ typedef enum _mjtMeshType {
 
 
 // error information
-class mjCError {
+class [[nodiscard]] mjCError {
  public:
   mjCError(const mjCBase* obj = 0,
            const char* msg = 0,
diff --git a/src/xml/xml_urdf.cc b/src/xml/xml_urdf.cc
index c69015cd..eddbaff5 100644
--- a/src/xml/xml_urdf.cc
+++ b/src/xml/xml_urdf.cc
@@ -308,7 +308,7 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
   ReadAttrTxt(joint_elem, "type", text, true);
   jointtype = FindKey(urJoint_map, urJoint_sz, text);
   if (jointtype < 0) {
-    mjXError(joint_elem, "invalid joint type in URDF joint definition");
+    throw mjXError(joint_elem, "invalid joint type in URDF joint definition");
   }
   ReadAttrTxt(joint_elem, "name", jntname, true);
 
@@ -317,7 +317,7 @@ void mjXURDF::Joint(XMLElement* joint_elem) {
   ReadAttrTxt(elem, "link", name, true);
   parent = (mjCBody*) model->GetWorld()->FindObject(mjOBJ_BODY, name);
   if (!parent) {                      // SHOULD NOT OCCUR
-    mjXError(elem, "invalid parent name in URDF joint definition");
+    throw mjXError(elem, "invalid parent name in URDF joint definition");
   }
 
   // get child=this, check
diff --git a/src/xml/xml_util.h b/src/xml/xml_util.h
index 302eea43..02c210a3 100644
--- a/src/xml/xml_util.h
+++ b/src/xml/xml_util.h
@@ -33,7 +33,7 @@ void mjCopyError(char* dst, const char* src, int maxlen);
 
 
 // XML Error info
-class mjXError {
+class [[nodiscard]] mjXError {
  public:
   mjXError(const tinyxml2::XMLElement* elem = 0,
            const char* msg = 0,