Why do I receive an error about number of output arguments when using an MATLAB file S-function in Simulink 6.0 (R14) which simulates correctly in earlier versions?

I receive an error about number of output arguments when using an MATLAB file S-function in Simulink 6.0 (R14) which simulates correctly in earlier versions.

I have a model which contains an MATLAB file S-function created in MATLAB 6.5.1 (R13SP1). This function simulates with no errors when ran in Simulink 5.1 (R13SP1) and earlier versions. However, when I attempt to simulate the same model and S-function in Simulink 6.0 (R14), I receive the following error:

 Error in 'untitled/S-Function' while executing MATLAB file

S-function 'my_sfun', flag = 0 (initialize), at start 

 of simulation. MATLAB error message:

 One or more output arguments not assigned during call 

 to '$MATLAB\work\my_sfun.m (my_sfun)'

(where $MATLAB = the MATLAB root directory on your machine)

Answer 1

[MathWorks Support Team]

In Simulink 6.0 (R14), the variable str must be initialized in the case where flag = 0 (Initialization) when it was not necessary in earlier versions. As a workaround, try adding:

str = [];

to the case where flag = 0 in your MATLAB file S-function. Also, you can use

[sys,x0,str, ts] = mdlInitializeSizes;

and declare str in mdlInitializeSizes. This is the approach given in the example S-function template sfuntmpl.m.