From 5a50be4e1554c6f96ff52fdbda5ba1c890d18a6d Mon Sep 17 00:00:00 2001
From: Andrey Kleshchev <andreykproductengine@lindenlab.com>
Date: Mon, 14 Jul 2025 18:47:03 +0300
Subject: #4294 Make upload order more deterministic #2

---
 indra/newview/llmeshrepository.cpp | 19 ++++++-------------
 indra/newview/llmeshrepository.h   | 17 ++++++++++++++++-
 2 files changed, 22 insertions(+), 14 deletions(-)

(limited to 'indra')

diff --git a/indra/newview/llmeshrepository.cpp b/indra/newview/llmeshrepository.cpp
index 6236df1a13..142a3dac39 100644
--- a/indra/newview/llmeshrepository.cpp
+++ b/indra/newview/llmeshrepository.cpp
@@ -2699,18 +2699,11 @@ void LLMeshUploadThread::wholeModelToLLSD(LLSD& dest, bool include_textures)
 
     S32 instance_num = 0;
 
-    // Upload should happen in deterministic order, so sort instances by model name.
-    // Note: probably can sort by mBaseModel->mSubmodelID here as well to avoid
-    // running over the list twice.
-    std::vector<std::pair<LLModel*, instance_list>> sorted_instances(mInstance.begin(), mInstance.end());
-    std::sort(sorted_instances.begin(), sorted_instances.end(),
-        [](const std::pair<LLModel*, instance_list>& a, const std::pair<LLModel*, instance_list>& b)
-    {
-        return a.first->mLabel < b.first->mLabel;
-    });
-
-    // Handle models, ignore submodels for now
-    for (auto& iter : sorted_instances)
+    // Handle models, ignore submodels for now.
+    // Probably should pre-sort by mSubmodelID instead of running twice.
+    // Note: mInstance should be sorted by model name for the sake of
+    // deterministic order.
+    for (auto& iter : mInstance)
     {
         LLMeshUploadData data;
         data.mBaseModel = iter.first;
@@ -2869,7 +2862,7 @@ void LLMeshUploadThread::wholeModelToLLSD(LLSD& dest, bool include_textures)
     }
 
     // Now handle the submodels.
-    for (auto& iter : sorted_instances)
+    for (auto& iter : mInstance)
     {
         LLMeshUploadData data;
         data.mBaseModel = iter.first;
diff --git a/indra/newview/llmeshrepository.h b/indra/newview/llmeshrepository.h
index 0847c29d0d..4c3901408f 100644
--- a/indra/newview/llmeshrepository.h
+++ b/indra/newview/llmeshrepository.h
@@ -674,7 +674,22 @@ public:
     typedef std::vector<LLModelInstance> instance_list;
     instance_list   mInstanceList;
 
-    typedef std::map<LLPointer<LLModel>, instance_list> instance_map;
+    // Upload should happen in deterministic order, so sort instances by model name.
+    struct LLUploadModelInstanceLess
+    {
+        inline bool operator()(const LLPointer<LLModel>& a, const LLPointer<LLModel>& b) const
+        {
+            if (a.isNull() || b.isNull())
+            {
+                llassert(false); // We are uploading these models, they shouldn't be null.
+                return true;
+            }
+            // Note: probably can sort by mBaseModel->mSubmodelID here as well to avoid
+            // running over the list twice in wholeModelToLLSD.
+            return a->mLabel < b->mLabel;
+        }
+    };
+    typedef std::map<LLPointer<LLModel>, instance_list, LLUploadModelInstanceLess> instance_map;
     instance_map    mInstance;
 
     LLMutex*        mMutex;
-- 
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