MATLAB Editor Code Analyzer

For the following code

x=1;
save('x','x')
x=2;

the MATLAB Editor Code Analyzer warns

"The value assigned to variable 'x' might be unused." I have clearly used it; I saved it to the file 'x.mat'. This bugs me, I'd like to see a nice green box telling me my code is clean.

Answer 1

[Rick Rosson]

Add the %#ok pragma at the end of the line:

   x = 2;   %#ok

HTH.

[Alan]

Thanks, I found it at the same time. Actually, the comment should go on the line

x=1;

Answer 2

[Honglei Chen]

The code analyzer cannot link 'x' to x because the former may just be a character and has nothing to do with the variable. You can get around this by right clicking the warning and suppressing the warning from the editor.

[Alan]

That doesn't seem to work on my system. I am using OS X.

[Alan]

but terminating my line with %#ok does work. Thanks for the lead.

Answer 3

[Rick Rosson]

Technically speaking (perhaps hyper-technically), you have not used the variable x. What you have done is to call a function and pass into that function two literal string constants. You have not passed any variables into the function.

So, the MATLAB Code Analyzer is actually correct. That being said, you are rightly disappointed by this outcome in this case. The reality is that the Code Analyzer does a really good job helping programmers write better code, but it is not perfect in all cases. MATLAB is an extremely flexible and forgiving language that allows programmers to do amazing things. As a consequence, it is not possible for any static code analyzer to detect every possible issue and also never issue a false alarm.

[Walter Roberson]

And remember, you might have a completely different save.m on your MATLAB path before the built-in routine that writes values to a file. Paths are dynamically adjustable, so this is not something that is decidable by a checker that does static code analysis.

Answer 4

[Alan]

Terminating the line with the comment

%#ok

suppresses the warning.