MATLAB: Is MATLAB /Simulink (R2009b) crashing during code generation but simulation works fine, with a model having Level 2 C S-function

MATLAB

I have a model with a Level 2 C S-function in it.

The simulation runs fine, but code generation fails. When working with S-function, MATLAB generates code even during simulation, hence why during code generation does it crashes.

There is no crash dump and it is a silent crash.

Best Answer

There can be extra section of S-function, which runs only during Code generation. This can be defined using MDL_RTW.

Furthermore, MATLAB was crashing because of freeing of incorrect memory inside the MDL_RTW section.

The errorneous code was :

#if defined (MATLAB_MEX_FILE)    /* Is this file being compiled as a MEX-file? */
      #define MDL_RTW
/* Function: mdlRTW ===========================================================
   */
      static void mdlRTW(SimStruct *S)
{
      boolean_T err = 0;
      int_T     status  = mxGetNumberOfElements(STATUS_PARAM(S));
      int_T     index = mxGetNumberOfElements(INDEX_PARAM(S));
      char_T    *statusStr;
      char_T    *indexStr;
      if ((statusStr=(char_T*)malloc(status)+1) == NULL ||
              (indexStr=(char_T*)malloc((index*5)+2+1)) == NULL) {
              ssSetErrorStatus(S,"Memory allocation error in mdlRTW");
              return;
          }
.... %extra lines of code
      free(indexStr);
      free(statusStr);
}
#endif /* MDL_RTW */

The issue is during the memory allocation call:

statusStr=(char_T*)malloc(status)+1

Ideally it should be (Corrected) :

statusStr=(char_T*)malloc(status+1)

Notice, the difference in where the paranthesis closes for MALLOC. In the errorneous code, freeing a incorrect address was leading to a silent crash.

Related Solutions

MATLAB: How to allocate and free memory for a PWork vector in a C-MEX S-function

First, the S-Function needs to specify how many PWork vectors it needs (using ssSetNumPWork) either in mdlInitializeSizes or in mdlSetWorkWidths. Simulink calls the above functions in the S-Function at the beginning of the model initialization stage (internally we refer to this part of the initialization stage as the compile phase). Towards the end of model initialization stage (internally we refer to this part of the initialization stage as the link phase), Simulink allocates the specified number of PWorks. Upon completing the model initialization stage, Simulink calls the S-Function's mdlStart. In the mdlStart function, the S-Function can allocate memory and store a pointer to it in the PWork array. The following code snippet illustrates specifying, allocating, using, and freeing memory using PWorks.

mdlInitializeSizes(SimStruct* S) 
{ 
/* snip */
ssSetNumPWork(S, 1);
/* snip */ 
}
mdlStart(SimStruct* S) 
{ 
/* snip */
void* ptr = malloc(1024 /* number of bytes */); 
if (ptr == NULL) { 
/* report memory allocation error */ 
ssSetErrorStatus(S, "Memory allocation error"); 
return; 
} 
ssSetPWorkValue(S, 0, ptr);
/* snip */ 
}
mdlOutputs(SimStruct* S, int_T tid) 
{ 
void* ptr = ssGetPWorkValue(S, 0);
/* snip */ 
}
mdlTerminate(SimStruct* S) 
{ 
/* snip */
/* free the memory allocated in mdlStart */ 
if (ssGetPWork(S) != NULL) { 
void* ptr = ssGetPWorkVale(S,0); 
if (ptr != NULL) free(ptr); 
}
/* snip */ 
}

For a more complete example on using PWork vectors please look at the following example in the documentation.

http://www.mathworks.com/help/releases/R2009b/toolbox/simulink/sfg/bre1pj2.html#bre1ps0

MATLAB: How to resolve S-function mdlRTW error during code generation

I though I needed to mdlRTW function to produce code for the rapid accelerator. However, this is not necessary. Simply deleting this part of the S-function solved the problem

Best Answer

Related Solutions

MATLAB: How to allocate and free memory for a PWork vector in a C-MEX S-function

MATLAB: How to resolve S-function mdlRTW error during code generation

Related Question