Problem with C-MEX S-function and atoi (pointers)

Hello everybody,

I have a problem with a C S-function code. After trying many times, my mdlOutputs code is in the momment the following one:

static void mdlOutputs(SimStruct *S, int_T tid)
{
  int Input_Node_A_value, Input_Node_B_value, Input_Node_C_value, B_Failure_value, C_Failure_value;
  char in_nodeA_char, in_nodeB_char, in_nodeC_char, in_failB_char, in_failC_char;
  char *in_nodeA_char_ptr = &in_nodeA_char, *in_nodeB_char_ptr = &in_nodeB_char, *in_nodeC_char_ptr = &in_nodeC_char, *in_failB_char_ptr = &in_failB_char, *in_failC_char_ptr = &in_failC_char;

        // 5 input ports (boolean):
    InputBooleanPtrsType Input_Node_A_ptrs = ssGetInputPortSignalPtrs(S,0);
    InputBooleanPtrsType Input_Node_B_ptrs = ssGetInputPortSignalPtrs(S,1);
    InputBooleanPtrsType Input_Node_C_ptrs = ssGetInputPortSignalPtrs(S,2);
    InputBooleanPtrsType B_Failure_ptrs = ssGetInputPortSignalPtrs(S,3);
    InputBooleanPtrsType C_Failure_ptrs = ssGetInputPortSignalPtrs(S,4);

  // 5 Output ports (boolean):
  boolean_T *Voted_Output = ssGetOutputPortSignal(S,0);
  boolean_T *ExactVotingLocalInputFailure = ssGetOutputPortSignal(S,1);
  boolean_T *VotingNoInputsFailure = ssGetOutputPortSignal(S,2);

    // display inputs
    ssPrintf("INPUTS ORIGINALES\n");
    ssPrintf("NodeA: %d    ", *Input_Node_A_ptrs[0]);
    ssPrintf("NodeB: %d    ", *Input_Node_B_ptrs[0]);
    ssPrintf("NodeC: %d    ", *Input_Node_C_ptrs[0]);
    ssPrintf("FailB: %d    ", *B_Failure_ptrs[0]);
    ssPrintf("FailC: %d\n", *C_Failure_ptrs[0]);

        // Save the value of the input ports:
         Input_Node_A_value = *Input_Node_A_ptrs[0];
    Input_Node_B_value = *Input_Node_B_ptrs[0];
    Input_Node_C_value = *Input_Node_C_ptrs[0];
    B_Failure_value = *B_Failure_ptrs[0];
    C_Failure_value = *C_Failure_ptrs[0];

      // Convert the value of the inputs to characters:
      itoa(Input_Node_A_value, in_nodeA_char_ptr, 10);
      itoa(Input_Node_B_value, in_nodeB_char_ptr, 10);
      itoa(Input_Node_C_value, in_nodeC_char_ptr, 10);
      itoa(B_Failure_value, in_failB_char_ptr, 10);
      itoa(C_Failure_value, in_failC_char_ptr, 10);

    //display conversion results
    ssPrintf("INPUTS TRAS CAMBIO\n");
    ssPrintf("NodeA: %c    ", *in_nodeA_char_ptr);
    ssPrintf("NodeB: %c    ", *in_nodeB_char_ptr);
    ssPrintf("NodeC: %c    ", *in_nodeC_char_ptr);
    ssPrintf("FailB: %c    ", *in_failB_char_ptr);
    ssPrintf("FailC: %c\n", *in_failC_char_ptr);

      // Just write a 0 in the outputs.
      *Voted_Output = 0;
      *ExactVotingLocalInputFailure = 0;
      *VotingNoInputsFailure = 0;

}

I don´t know what is wrong with the code, but Matlab executes it correctly once (well, not so correctly, it does some strange things when converting the values), and then it breaks with the following diagnostic:

Warning: Using a default value of 0.2 for maximum step
size.  The simulation step size will be equal to or less
than this value.  You can disable this diagnostic by
setting 'Automatic solver parameter selection' diagnostic
to 'none' in the Diagnostics page of the configuration
parameters dialog.
INPUTS ORIGINALES
NodeA: 1    NodeB: 1    NodeC: 1    FailB: 0    FailC: 0
INPUTS TRAS CAMBIO
NodeA: 1    NodeB:     NodeC: 1    FailB: 0    FailC: 

Checked all 6 cache memory tables. Found no corrupted tables.
Saving minidump to file C:\DOCUME~1\IAYEST~1\CONFIG~1\Temp\matlab_crash_dump.2836.0.dmp

------------------------------------------------------------------------
       Segmentation violation detected at Fri May 13 09:06:47 2011
------------------------------------------------------------------------

Configuration:
  MATLAB Version:   7.5.0.342 (R2007b)
  MATLAB License:   282444
  Operating System: Microsoft Windows XP
  Window System:    Version 5.1 (Build 2600: Service Pack 3)
  Processor ID:     x86 Family 15 Model 6 Stepping 4, GenuineIntel
  Virtual Machine:  Java 1.6.0 with Sun Microsystems Inc. Java HotSpot(TM) Client VM mixed mode
  Default Charset:  windows-1252

Register State:
  EAX = 0000001b  EBX = 18f7dcdb
  ECX = cc32a696  EDX = 7a8531c4
  ESI = 18f7dcd3  EDI = 12faf050
  EBP = 00ceaec4  ESP = 00ceaea8
  EIP = 7abc2f65  FLG = 00010246

Stack Trace:
  [0] libut.dll:_mw_free32(0x18f7dcdb, 0x00ceaf00, 0x6faab51c, 0x18f7dcdb) + 117 bytes
  [1] libut.dll:_utFree(0x18f7dcdb, 0x18f7dcdb, 0x015e5620, 0) + 80 bytes
  [2] libmwsimulink.dll:class slErrMsgQueue * __cdecl CMexSFcnOutputFcn(struct slSFcnInfo *)(0x78132c78, 5, 0x00ceaf58, 0x78132e24) + 1644 bytes
  [3] 0x00ceaf58

Please follow these steps to report this problem to The MathWorks so we
have the best chance of correcting it:

The next time MATLAB is launched under typical usage, a dialog box will
open to help you send the error log to The MathWorks. Alternatively, you
can send an e-mail to [e-mail] with the following file attached:
    C:\DOCUME~1\IAYEST~1\CONFIG~1\Temp\matlab_crash_dump.2836

If the problem is reproducible, please submit a Service Request via:
    http://www.mathworks.com/support/contact_us/ts/help_request_1.html

A technical support engineer might contact you with further information.

Thank you for your help. Save your workspace and restart MATLAB.

Saving minidump to file C:\DOCUME~1\IAYEST~1\CONFIG~1\Temp\matlab_crash_dump.2836.1.dmp
Windows exception while processing the previous exception

Segmentation violation occurred within signal handler.
Unable to complete stack trace (stack was probably corrupted)

Please follow these steps to report this problem to The MathWorks so we
have the best chance of correcting it:

The next time MATLAB is launched under typical usage, a dialog box will
open to help you send the error log to The MathWorks. Alternatively, you
can send an e-mail to [e-mail] with the following file attached:
    C:\DOCUME~1\IAYEST~1\CONFIG~1\Temp\matlab_crash_dump.2836

If the problem is reproducible, please submit a Service Request via:
    http://www.mathworks.com/support/contact_us/ts/help_request_1.html

A technical support engineer might contact you with further information.

Thank you for your help.

Saving minidump to file C:\DOCUME~1\IAYEST~1\CONFIG~1\Temp\matlab_crash_dump.2836.2.dmp
Windows exception while processing the previous exception

Segmentation violation occurred within signal handler.
Unable to complete stack trace (stack was probably corrupted)

Please follow these steps to report this problem to The MathWorks so we
have the best chance of correcting it:

I don´t know what am I doing wrong, can anybody help me?

Thank you in advance.

Answer 1

[Jan]

This must fail:

char in_nodeA_char;
char *in_nodeA_char_ptr = &in_nodeA_char;
itoa(Input_Node_A_value, in_nodeA_char_ptr, 10);

"in_nodeA_char" is a single char value, which is referred by "in_nodeA_char_ptr". But by itoa, you write more than 1 character to the string in general. Therefore itoa is deprecated e.g. since MSVC2005. itoa_s would reveal such bugs. Either use this, or expand at least "in_nodeA_char" to a string with the needed number of characters.

[Iban]

Hi Jan,

I don´t really need the 'in_nodeA_char_ptr' pointer. I just want to convert the integer 'Input_Node_A_value' into a char and store it in 'in_nodeA_char'. Both int and char are single values, actually they only can be '0' or '1'.

I tried with "in_nodeA_char = (char)Input_Node_A_value;" but it doesn´t work, because it transforms the integer value "1" in something like "1 ''". How can I make that conversion?

As you see I don´t know very much about C...

Answer 2

[Iban]

Hello,

I have tried with in_nodeA_char = Input_Node_A_value + 0x30; and the problem has gone.

Thank you for answering.