bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoid mismatches #2096

Caball009 · 2026-01-12T11:53:13Z

Closes Misplaced OCL Mismatch #429

GeneralsGameCode/GeneralsMD/Code/GameEngine/Source/GameLogic/Object/ObjectCreationList.cpp

Lines 1385 to 1391 in 25e3602

    
           Coord3D resultPos; 
        
           FindPositionOptions fpOptions; 
        
           fpOptions.minRadius = GameLogicRandomValueReal(m_minDistanceAFormation, m_minDistanceBFormation); 
        
           fpOptions.maxRadius = m_maxDistanceFormation; 
        
           fpOptions.flags = FPF_USE_HIGHEST_LAYER; 
        
           ThePartitionManager->findPositionAround(pos, &fpOptions, &resultPos); 
        
           doStuffToObj( debris, m_names[pick], &resultPos, mtx, orientation, sourceObj, lifetimeFrames );

This code is called for the GLA Rebel Ambush special power. resultPos remains uninitialized if findPositionAround fails (returns false), making the behavior undeterministic (i.e. may cause mismatches). This can be tested when calling the special power on a large body of water. The m_maxDistanceFormation is quite large for this special power, so it has to be a large body of water. Mountainous terrain probably also works.

For the Contra mod, this is called for the USA Air Force General special power that spawns Comanches, which has a much lower test radius so findPositionAround is more likely to fail.

TODO:

Replicate in Generals
Maybe check large number of replays and log uninitialized values

…d mismatches

helmutbuhler · 2026-01-20T08:17:58Z

Based on #2095, I tested this on 1800 replays and found no mismatch.

Caball009 · 2026-01-20T10:43:43Z

Based on #2095, I tested this on 1800 replays and found no mismatch.

Thanks, that's good news.

greptile-apps · 2026-01-20T10:46:36Z

Greptile Summary

Fixed a critical determinism bug where resultPos could remain uninitialized when findPositionAround fails to find a valid spawn location (e.g., when spawning units over large water bodies or mountainous terrain). The uninitialized variable caused non-deterministic behavior leading to multiplayer mismatches.

Added return value check for findPositionAround in spread formation logic
Falls back to center position (*pos) when no valid position is found
Added DEBUG_CRASH warning for RETAIL_COMPATIBLE_CRC builds to alert developers when this fallback path is taken with unpatched clients
Resolves issue Misplaced OCL Mismatch #429 where OCL objects would spawn at unexpected locations (bottom-left of map) causing mismatches

Confidence Score: 5/5

This PR is safe to merge with minimal risk
The fix correctly addresses a well-documented uninitialized variable bug by checking the return value and providing a sensible fallback. The change is minimal, focused, and follows patterns used elsewhere in the codebase. The added debug assertion helps identify potential compatibility issues without affecting release builds.
No files require special attention

Important Files Changed

Filename	Overview
GeneralsMD/Code/GameEngine/Source/GameLogic/Object/ObjectCreationList.cpp	Fixed critical uninitialized variable bug by checking return value of `findPositionAround` and falling back to center position when no valid position is found

Sequence Diagram

sequenceDiagram
    participant OCL as ObjectCreationList
    participant PM as PartitionManager
    participant Obj as Debris Object
    
    OCL->>OCL: Check m_spreadFormation flag
    alt m_spreadFormation is true
        OCL->>OCL: Initialize resultPos (Coord3D)
        OCL->>OCL: Setup FindPositionOptions
        OCL->>PM: findPositionAround(pos, fpOptions, &resultPos)
        alt Position found
            PM-->>OCL: return true (resultPos set)
        else Position not found (e.g., large water body)
            PM-->>OCL: return false (resultPos uninitialized)
            Note over OCL: OLD: Use uninitialized resultPos (MISMATCH!)
            Note over OCL: NEW: Set resultPos = *pos (fallback)
            OCL->>OCL: DEBUG_CRASH warning (if RETAIL_COMPATIBLE_CRC)
        end
        OCL->>Obj: doStuffToObj(debris, name, &resultPos, ...)
    else m_spreadFormation is false
        OCL->>Obj: doStuffToObj(debris, name, pos, ...)
    end

xezon

Looks reasonable.

Needs to be replicated in Generals.

GeneralsMD/Code/GameEngine/Source/GameLogic/Object/ObjectCreationList.cpp

xezon

This is one of currently 3 open PRs with fixes for uninitialized variables, which come with a small risk of introducing new mismatches. These should be merged together without other PRs in between:

Caball009 · 2026-01-23T19:44:14Z

Replicated in Generals. Ready to be merged whenever the other PRs are.

bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoi…

8bf509a

…d mismatches

Caball009 added Bug Something is not working right, typically is user facing Major Severity: Minor < Major < Critical < Blocker Gen Relates to Generals ZH Relates to Zero Hour Stability Concerns stability of the runtime labels Jan 12, 2026

Caball009 mentioned this pull request Jan 12, 2026

bugfix(ocl): Fix GLA Rebel Ambush units spawning in water/cliffs and dying immediately #1882

Closed

Caball009 marked this pull request as ready for review January 20, 2026 10:43

xezon approved these changes Jan 22, 2026

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Removed branch for release build.

4b1dc5c

xezon requested changes Jan 23, 2026

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Replicated in Generals.

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bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoid mismatches #2096

bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoid mismatches #2096

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Caball009 commented Jan 12, 2026 •

edited

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helmutbuhler commented Jan 20, 2026

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Greptile Summary

Sequence Diagram

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	Coord3D resultPos;
	FindPositionOptions fpOptions;
	fpOptions.minRadius = GameLogicRandomValueReal(m_minDistanceAFormation, m_minDistanceBFormation);
	fpOptions.maxRadius = m_maxDistanceFormation;
	fpOptions.flags = FPF_USE_HIGHEST_LAYER;
	ThePartitionManager->findPositionAround(pos, &fpOptions, &resultPos);
	doStuffToObj( debris, m_names[pick], &resultPos, mtx, orientation, sourceObj, lifetimeFrames );

bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoid mismatches #2096

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bugfix(ocl): Fix uninitialized variable in ObjectCreationList to avoid mismatches #2096

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Caball009 commented Jan 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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TODO:

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helmutbuhler commented Jan 20, 2026

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Confidence Score: 5/5

Important Files Changed

Sequence Diagram

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Caball009 commented Jan 23, 2026

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Caball009 commented Jan 12, 2026 •

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