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MLintFailureFiles or: Why can't I save my m-file?!

February 1, 2012 No Comments

A short while ago, I was working at a client’s location on some project, when a very strange thing happened: when editing an m-file in the Matlab editor, the mlint process (the one that reports errors and warnings on the right-hand side of the editor) suddenly decided that it has had enough with this specific file. It labeled the entire file as red, meaning that it has errors that prevent it from being run, although as far as we could both see the file was valid and had no syntax errors and actually ran fine.
Here’s a screenshot of the message that mlint reported in the editor:

erroneous mlint error report
erroneous mlint error report

Mlint’s confusion would not have bothered us if it were not for a seemingly-related issue: When we tried to save the file, the Matlab editor would only allow us to save the file under a different name. When we attempted to restart Matlab, the same behavior repeated for this file, and we could not proceed with our actual work, modifying and saving our m-file.
Not easily intimidated, I tried saving the file under a different name in the editor, then renaming it back outside Matlab. No good, same problem.

MLintFailureFiles or: yet another use for prefdir

The clue that eventually led to the fix was that somehow Matlab remembered the “faulty” state of the m-file even after I restarted Matlab. Matlab likes to store persistent cross-session information in a single folder, which is the user’s prefdir folder. I have used this to my advantage only a few weeks ago, when I explained how to use the stored editor state file that is stored in that folder.
My hunch was that Matlab might store the mlint’s “faulty” m-file state somewhere in there. I didn’t have to look very far: one of the files most recently modified had the tell-tale name of MLintFailureFiles. This turns out to be an empty file that contains the full pathname of the “faulty” m-files, one file per line.
The fix turned out to be very easy: simply remove my file from the MLintFailureFiles file (or delete MLintFailureFiles entirely) and restart Matlab. Problem solved – everything back to normal. Resume breathing.

Undocumented? well, not exactly

I then went back to the suggestion in the mlint message and true enough I found related information in the documentation, at the bottom of the doc-page for using mlint. This is from R2008a’s doc page:

About M-Lint and Unexpected MATLAB® Termination
Under some circumstances, when you are editing an M-file, M-Lint can cause the MATLAB session to terminate unexpectedly. The next time you start MATLAB, it displays the following message and disables M-Lint for the M-file that was open in the editor when MATLAB terminated.

M-Lint caused your previous MATLAB session to terminate unexpectedly.
Please send this message and file name to The MathWorks.
See "About M-Lint and Unexpected MATLAB Termination" in the MATLAB documentation for details.

If you want, while waiting for a response from The MathWorks™, you can attempt to reenable M-Lint for the file by following these steps:

  1. In the Editor, reopen the file that you were editing when MATLAB terminated.
  2. Remove the lines of code that you believe M-Lint could not handle.
  3. In a text editor, open the MLintFailureFiles file in your preferences directory. (This is the directory that MATLAB returns when you run prefdir.)
  4. Save and reopen the M-file.

As you can see, this is not very helpful because it’s missing the step of actually editing (or deleting) the MLintFailureFiles file.
Additional documentation of this issue and workaround can be found in two separate Mathworks technical notes: here and here.
A Matlab user has even created a utility on the File Exchange that simply deletes this file, basing his work on the first note above.
The second note indicates that the problem (and workaround) occur in Matlab releases R2008a-R2010b, and indeed the above-mentioned issue (and workaround) can no longer be found in the latest docs (as far as I could see). However, even if this issue (and MLintFailureFiles) may no longer be relevant in the latest Matlab releases, we may still see MLintFailureFiles in our prefdir, because the prefdir contents are automatically copied from the previous release whenever we install a newer Matlab release.

Related posts:

  1. Improving save performance – There are many different ways of improving Matlab's standard save function performance. ...
  2. AppDesigner's mlapp file format – MLAPP files created by AppDesigner can be inspected and manipulated outside AppDesigner. ...
  3. File deletion memory leaks, performance – Matlab's delete function leaks memory and is also slower than the equivalent Java function. ...
  4. Recovering previous editor state – Recovering the previous state of the Matlab editor and its loaded documents is possible using a built-in backup config file. ...
  5. Parsing mlint (Code Analyzer) output – The Matlab Code Analyzer (mlint) has a lot of undocumented functionality just waiting to be used. ...
  6. Plot line transparency and color gradient – Static and interpolated (gradient) colors and transparency can be set for plot lines in HG2. ...
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Recent Comments
  • Iñigo (2 days 15 hours ago): Thanks Yair. I didn’t realize it was posted just above. It would be great to know about a solution soon
  • Yair Altman (3 days 22 hours ago): @Iñigo – your query is related to Seth’s question above. We can access the currently-browsed URL in JavaScript (for example: jBrowserPanel.executeScript...
  • Iñigo (5 days 14 hours ago): I am looking for setting a UI that allows following process: opening a web site, navigate inside this web site and at some specific moments (i.e. when the figure is closed or a button...
  • Nicholas (12 days 19 hours ago): Yair, this works wonderfully! I can’t thank you enough!
  • Collin (14 days 23 hours ago): Seth Good point, I am using 2022b, mathworks seems to have started using CEF browsers from 2019a, best I can tell. take a look at the package com.mathworks.toolbox.matla...
  • Seth (15 days 15 hours ago): Collin, What version of MATLAB are you using?
  • Collin (20 days 21 hours ago): Seth, I have had some success executing javascript that requires no return value by executing it directly (sort of) on the org.cef.browser.CefBrowser that a...
  • Coo Coo (22 days 16 hours ago): FFT-based convolution is circular whereas MATLAB’s conv functions have several options (‘valid’, ‘same’, ‘full’) but unfortunately not...
  • Seth (22 days 19 hours ago): No luck with removing the space.
  • Seth (22 days 21 hours ago): The javascript code works fine running the application from the 2019b desktop version and the 2016b deployed version.
  • Seth (22 days 21 hours ago): I have been using this browser functionality in 2016b because it works fully in deployed applications in that version. However, because of Java 7 being flagged as a security risk, I...
  • Yair Altman (22 days 21 hours ago): I’ve never tested javascript callbacks, but perhaps you should try removing the extra space after the “matlab:” protocol specifier. Does it make any difference?
  • Seth (22 days 22 hours ago): I have been using this functionality in 2016b since it works in deployed applications and have not had a reason to need to upgrade but with java 7 being flagged as a security risk I am...
  • KEVIN (42 days 22 hours ago): I apologize, I intended my response to fall under ‘T’ but did not seem to work. I was referring to the bit of code posted by ‘T’ regarding the toolgroup and...
  • Yair Altman (42 days 23 hours ago): It is not clear from your comment which code exactly you are referring to and what you see differently in 19b vs. 20b, so I cannot assist with your specific query. In general I...
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