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acess violatione error

Jul 30, 2011 at 8:31am
mgm11 (18)
i keep getting an acess violation. it has to do with my parameters, or initialising of parametrers. can anyone get my code to work?

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#include <iostream>
#include <sstream>
#include <stdio.h>
#include <cstdlib>
#include <string>
#include <string.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

stringstream stst;
string str ;
int cpp_do_ousb_command(string *str) //===========
{ FILE *fpipe ;
if ( !(fpipe = (FILE*)popen(str->c_str(),"r")))
{ cout << "pipe error" << endl ;
exit(0) ;
}

char line[100] ;
fgets( line, sizeof line, fpipe) ;
pclose(fpipe) ;
*str = line ; // caller can see whole ousb string in str.
return( atoi(line)) ; // return int version of string.
}


int main(int argc, char *argv[])
{
    
    const double MAXRANGE = 100; //maxrange
    const double MINRANGE = 0;//minrange

int pwn_freq;

    int pwm_duty;

    double param1=atoi(argv[1]);
    double param2=atoi(argv[2]);
    

  if (argc == 1)  // no parameters print this line.
    { cout << "3333435, s3333435@student.rmit.edu.au, Matthew Merigan"<< endl ;
      
      return(0) ;
    }
     
    if(argc>3)
    {
      cout<<"P"<<endl;
      return(0);
    }
     
    if (strcmp(argv[1],"P") && strcmp(argv[1],"M") && strcmp(argv[1],"L") && strcmp(argv[1],"A"))
    {
       cout<<"I"<<endl;
       return 0;
    }               

/*hey its james why don’t we just use 

default:
           cout<<"I";
in stead of the code i’ve highlighted above “default” make all the values not present in the cases go to default were were we would have cout<<"I"; 

agreed.*/

     switch (argv[1][0])
    {
       case 'P':
       {

if(param2<MINRANGE||param2>MAXRANGE)
{
cout<<"r"<<endl;
return(0);
}
pwn_freq = 46 ; 
pwm_duty = 46 ; //changed
stst.str("") ; // clear if used before.
stst << pwn_freq ;
// note -r below ensures reply is just an integer.
str = "ousb -r pwm-freq 1 " + stst.str() ;
cout << cpp_do_ousb_command(&str) << endl ;

stst << pwm_duty ;
str = "ousb -r pwm 1 " + stst.str() ;
cout << cpp_do_ousb_command(&str) << "p"<<endl ;
     
     break;
   }
   
   case 'L':
       {
     
     break;
   }
   
   case 'A':
       {
     
     break;
   }
   
   case 'M':
       {
     
     break;
   }
default:

{

cout<<    "I"<<endl;
break;
}
}
   
system ("pause");
return(0) ;
}
Edit & run on cpp.sh
Jul 30, 2011 at 9:32am
Caligulaminus (201)
One could call this kind of post an access violation.

You need to be much more specific (what, where, when, error message...)
Jul 30, 2011 at 10:39am
andywestken (4094)
Well, the first access violation you might encounter is here:

1
2
 
    double param1=atoi(argv[1]);
    double param2=atoi(argv[2]);


Unless you always provide at least two command line parameters!

As it stand, running with less than two command line parameters will feel a null pointer to one or other of the atoi() calls.

If running without command line parameters, you need to add logic (using argc) to control your command line handling. I think you might need more logic further down, but I didn't look too closely.

Andy

P.S. "Real" C++ programmers prefer to pass by reference not pointer!
Jul 30, 2011 at 8:55pm
mgm11 (18)
you are right it is the seting of the parameters was where i found the problem, but how do i set them properly to make them logical?

sorry again

MGM
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