Unity Issue Tracker - Regression for "WebGL build is missing "malloc" and "free" functions when passing "-sERROR_ON_UNDEFINED

In Progress

Under Consideration for 6000.0.X, 6000.2.X, 6000.3.X

Fix In Review for 6000.4.X

Votes

0

Found in

6000.0.58f1

6000.1.0a2

6000.1.17f1

6000.2.6f2

6000.3.0a1

6000.4.0a1

6000.5.0a1

Issue ID

UUM-126250

Regression

Yes

Regression for "WebGL build is missing "malloc" and "free" functions when passing "-sERROR_ON_UNDEFINED_SYMBOLS=0" to emscriptenArgs"

-

Nov 06, 2025

This bug regressed: https://jira.unity3d.com/browse/UUM-74261
The fix is missing in emscripten in Unity 6.1-6.5.

Reproduction steps:

Open the attached “WebGLMissingMethodRepro.zip” project
Open the “SampleScene” scene (Assets > Scenes)
Build and Run for the WebGL (File > Build and Run)
Observe the Player in the browser and turn on Developer Tools (press F12)

Expected result: No errors are thrown
Actual result: “missing function: malloc” and “missing function: free” errors are thrown in the browser’s Console

Reproducible with versions: 6000.0.58f1, 6000.1.0a2, 6000.2.0a1, 6000.3.0a1, 6000.4.0a1, 6000.5.0a1
Not reproducible with versions: 6000.0.11f1, 6000.1.0a1

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Tested on (OS): MacOS 15.7.1

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Notes:

This PR needs to be ported to Emscripten 3.1.38.4-unity: https://github.com/Unity-Technologies/emscripten/pull/10 (missing in all branches after 3.1.38.1-unity)

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