From 188b04fba587d0072a4445d7dc40553091b82bcf Mon Sep 17 00:00:00 2001
From: Yuval Tassa <tassa@google.com>
Date: Thu, 8 Jun 2023 08:20:35 -0700
Subject: [PATCH] Use `std::stable_sort` in model compiler.

PiperOrigin-RevId: 538791034
Change-Id: I6c8eceffeb765a8a9801fee996d6ebf2964d8453
---
 src/user/user_mesh.cc  | 2 +-
 src/user/user_model.cc | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/user/user_mesh.cc b/src/user/user_mesh.cc
index 5debc32a..29b01be3 100644
--- a/src/user/user_mesh.cc
+++ b/src/user/user_mesh.cc
@@ -318,7 +318,7 @@ void mjCMesh::Compile(int vfs_provider) {
 
   // check for inconsistent face orientations
   if (!useredge.empty()) {
-    std::sort(useredge.begin(), useredge.end());
+    std::stable_sort(useredge.begin(), useredge.end());
     auto iterator = std::adjacent_find(useredge.begin(), useredge.end());
     if (iterator != useredge.end()) {
       invalidorientation.first = iterator->first+1;
diff --git a/src/user/user_model.cc b/src/user/user_model.cc
index 3f670a85..2e4c3bb1 100644
--- a/src/user/user_model.cc
+++ b/src/user/user_model.cc
@@ -2619,8 +2619,8 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, int vfs_provider) {
   }
 
   // sort pair, exclude in increasing signature order; reassign ids
-  sort(pairs.begin(), pairs.end(), comparePair);
-  sort(excludes.begin(), excludes.end(), compareBodyPair);
+  std::stable_sort(pairs.begin(), pairs.end(), comparePair);
+  std::stable_sort(excludes.begin(), excludes.end(), compareBodyPair);
   reassignid(pairs);
   reassignid(excludes);