Simulink crash after free(ptr) in mdlTerminate and pointers strange behavior.

Hi everyone!

I have a problem with a S-function that I'm using with Simulink.

Inside mdlStart I used malloc() to allocate memory in this way.

  static void mdlStart(SimStruct *S)
  {
    char *str = (char*)malloc(INPUT_SIZE+1);
    char *cut_str = (char*)malloc(INPUT_SIZE+1);
      if (str==NULL)
      {
            std::cout << "Memory problem!\n";
      }
      else if (cut_str==NULL)
      {
            std::cout << "Memory problem!\n";
      }
      else
      {
          ssSetUserData(S,str);
          ssSetUserData(S,cut_str); 
      }
  }

First question: is it ok?

Then, inside mdlOutputs I read the input vector and I stored it inside char *str.

static void mdlOutputs(SimStruct *S, int_T tid)
{  
    InputPtrsType u = ssGetInputPortSignalPtrs(S,0);
    InputUInt8PtrsType resp8 = (InputUInt8PtrsType)u;
    real_T *y0 = (real_T *) ssGetOutputPortRealSignal(S, 0);
    
    char* str = (char *)ssGetUserData(S);
    char* cut_str = (char *)ssGetUserData(S);
    
    for ( int i=0; i<INPUT_SIZE; i++ )
    {  
     str[i]=*resp8[i];                  // Copy the resp8 vector inside *str.
    }
    str[INPUT_SIZE]='\0';               // Null-terminated char

    for (int i=0; i<OUTPUT_SIZE;i++)
    {
    y0[i]=cut_str[i];                   // ??? This shows me the same values of str.
    }
}

Now, str stores the resp8 values and if I output this values are ok.

The problem is that if I output the values of cut_str (that I did no touch after mdlStart!!!) show me the same valus of str! How is possible??

Another problem is related to mdlTerminate when I try to free the memory!

static void mdlTerminate(SimStruct *S)
{
    char* str = (char *)ssGetUserData(S);
    char* cut_str = (char *)ssGetUserData(S);
    if (str!=NULL)
    {
        free(str);
        std::cout << "str memory free" ;
    }
    if (cut_str!=NULL)
    {
        free(cut_str);
        std::cout << "cut_str memory free!" ;
    }
}

During this last phase, Simulink stucks at 100% and after a few seconds it closes unexpectedly. (both Matlab and Simulink)

No errors, no warnings, no dialog box: nothing.

What am I doing wrong?

Thanks!