"File is not a mex file" error despite the settings seeming correct

I am trying to follow the Matlab examples on using mex. I first run

copyfile(fullfile(matlabroot,"extern","examples","mex","yprime.c"),".","f")

and this works, copying the file. I then run

mex yprime.c

which gives me the output

Building with 'MinGW64 Compiler (C)'.

Error using mex

'yprime.mexw64' is not a MEX file. For more information, see File is not a MEX file.

I have ensured that I am using the correct version of the compiler (6.3.0). I am using a 64-bit operating system with 64-bit MATLAB, and running

mexext

returns mexw64 as expected. So I am not sure what the issue could be. I have looked in the "see File is not a MEX file" section of the help and it did not help me resolve the issue.

[dpb]

There apparently is at least one other way to generate the message than just the wrong extension...

https://www.mathworks.com/matlabcentral/answers/1938709-invalid-mex-file#answer_1207184

I haven't tried mex'ing anything in years since they quit supporting any Fortran compiler other than Intel...

Answer 1

[Elliott]

Issue is resolved. The filepath for an executeable is longer than allowed by administration on my laptop and so it fails to execute correctly. Performing the same operations with a shorter filepath worked with no issues.

[dpb]

Good to know...that's one I wouldn't have thought of, for sure...

Answer 2

[Shivam Gothi]

Hello @Elliott

I have executed the code you provided in MATLAB R2022b, without encountering any errors. However, I have identified a few workarounds that might help resolve the issue.

Cause of the error:

If MATLAB cannot find all .DLL files referenced by a MEX file, it cannot load the MEX file. MATLAB displays the following error message:

Invalid MEX-file mexfilename:

The specified module could not be found.

where “mexfilename” is the module with the dependency error. This module cannot find its dependent libraries. To resolve this error, find the names of the dependent libraries, and determine if they are present on your system and on the system path.

For windows operating system, you can use “Dependency Walker Utility”.

Dependency Walker is a tool that tracks and logs files that are accessed when an executable launches. It can also track what files are being called by a DLL or SYS file. It is able to track file registration errors, access violations, invalid page faults or even missing files. It can be downloaded from the website:

https://www.dependencywalker.com

Refer to the below documentation to get more detailed explanation:

https://www.mathworks.com/help/matlab/matlab_external/invalid-mex-file-error.html

To know more about “Dependency walker utility”, refer:

https://techcommunity.microsoft.com/t5/ask-the-performance-team/analyze-application-failures-the-easier-way-with-dependency/ba-p/374648#:~:text=Once%20downloaded%20we%20just%20need,is%20an%20example%20of%20this.

you can also refer to the below MATLAB answer, which addresses the similar issue:

https://www.mathworks.com/matlabcentral/answers/1938709-invalid-mex-file

I hope it helps!

[Elliott]

Hi Shivam,

Thanks for the answer. There are no specific ones missing for the files I am trying to compile which is unfortunate.

I think the error you mentioned is a slightly different one to the one I am getting. I am getting

Error using mex

'yprime.mexw64' is not a MEX file. For more information, see File is not a MEX file.

rather than an error about missing dlls.