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How I solved Matlab/Simulink S-Function error: mexa64: GLIBCXX_3.4.xx not found

Problem

When trying to run a Simulink model that uses an S-Function compiled with mex, I encountered the following error:

Invalid MEX-file '/home/user/mysfunction.mexa64': /opt/matlab/R2025a/bin/glnxa64/../../sys/os/glnxa64/libstdc++.so.6: version `GLIBCXX_3.4.32' not found (required by /home/user/mysfunction.mexa64)

Solution

This error occurs because the version of libstdc++.so.6 that Matlab is using (/opt/matlab/R2025a/sys/os/glnxa64/libstdc++.so.6 in this case) is older than the one required by the compiled S-Function (which is used during compilation with mex).

In my case, Matlab comes with GLIBCXX_3.4.30 but my system libstdc++ is GLIBCXX_3.4.32. This is a very minor mismatch, the system library is ever so slightly newer (Ubuntu 24.04 LTS, 2025-08-06).

I resolved this issue by deleting the libstdc++.so.6 file in the Matlab directory since it works just as well with the system’s libstdc++.so.6 file.

Before attempting this solution, ensure you have a backup of the original file.

rm /opt/matlab/R2025a/sys/os/glnxa64/libstdc++.so.*

After that, you need to restart Matlab and also recompile your S-Function using mex. The error should have been resolved after that.