Subj : passing an 'int' to a thread
To   : comp.programming.threads
From : Huub
Date : Tue Jun 07 2005 10:13 pm

Hi,

With an example I took from the web I've tried to modify it so it passes 
an int (0, 4 or -4) to a thread. However, I get undefined references.

This is my code so far:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <iostream>
#include <cstdlib>
#include <memory>
#include <pthread.h>
#include <time.h>
#include "ftapi/ftapi.h"

using namespace std;
using namespace ftapi;

   // default interface connection
string device("");
ft_if_conn connection = FT_IC_LIB_USB;
IfOutputs out;
IfInputs inp;

void *MotorDraad(void *threadid)
{
   int *id_ptr, task_id;
   id_ptr = (int *)threadid;
   task_id = *id_ptr;
   cout << "Start MotorDraad" << endl;
   time_t start;
   time_t current;
   time(&start);
   try
   {
     auto_ptr<FtInterface> fti (ftGetIfFromFactory(device,
						  connection));
   // Initialspeed = 4
     FtMotorSpeed mSpeed1(task_id);
   // Initialspeed = 4
     FtMotorSpeed mSpeed2(task_id);
   // enable all motor outputs
     out.data[FT_MASTER]= 0xFF;
   // M1: not moving
     out.setMotorSpeed(FT_MASTER, FT_M1, mSpeed1);
   // M2: forward with velocity 4
     out.setMotorSpeed(FT_MASTER, FT_M2, mSpeed2);
     while (difftime(current,start) < 5.0)
     {
       time(&current);
       fti->writeAndReadAllData(out, inp);
     }
   }
   // anything went wrong
   catch (exception &x)
     {
       cout << x.what() << endl;
     }
}


int main(int argc, char *argv[])
{
   cout << "Start fase 1" << endl;

   pthread_t threads[1];
   int *task_ids[1];
   int rc, t;
   t = 0;
   int snelheid = 0;

   cout << "1 Thread gedeclareerd" << endl;

   cout << "fttestextension v0.4" << endl;

   if (1 == argc)
     {
       /* leave device name as defined above, since no
	 parameters given */
     }
   else if (((2 == argc) || (3 == argc)) &&
	   (string("-l")==(argv[1])))
     {
       if (3 == argc) device = argv[2];
       connection = FT_IC_LIB_USB;
     }
   else if (((2 == argc) || (3 == argc)) &&
	   (string("-u")==(argv[1])))
     {
       if (3 == argc)
	{
	  device = argv[2];
	}
       else
	{
	  device = "/dev/usb/robointerface0";
	}
       connection = FT_IC_USB;
     }
   else
     {
       return EXIT_FAILURE;
     }

   // now let's go!
   cout << "opening fischertechnik interface \"" << device << "\""
        << endl;
   task_ids[t] = (int *) malloc(sizeof(int));
   *task_ids[t] = t;
   while (snelheid != 8)
     {
       cin >> snelheid;
       cout << "Aanmaken thread" << endl;
       rc = pthread_create(&threads[t], NULL, MotorDraad,
			  (void *)task_ids[t]);
     }
   pthread_exit(NULL);
   return EXIT_SUCCESS;
}

// EOF

I compile it with:

  g++ -lftapi -lusb ffTestInterface_thread_args.cpp -o 
ffTestInterFace_thread_args -pthread

Errors:

/tmp/ccbRjnRM.o(.text+0x6d): In function `MotorDraad(void*)':
: undefined reference to 
`ftapi::ftGetIfFromFactory(std::basic_string<char, 
std::char_traits<char>, std::allocator<char> >, ftapi::ft_if_conn)'
/tmp/ccbRjnRM.o(.text+0xc3): In function `MotorDraad(void*)':
: undefined reference to `ftapi::FtMotorSpeed::FtMotorSpeed[in-charge](int)'
/tmp/ccbRjnRM.o(.text+0xd5): In function `MotorDraad(void*)':
: undefined reference to `ftapi::FtMotorSpeed::FtMotorSpeed[in-charge](int)'
/tmp/ccbRjnRM.o(.text+0xf1): In function `MotorDraad(void*)':
: undefined reference to 
`ftapi::IfOutputs::setMotorSpeed(ftapi::ft_module_type, ftapi::ft_motor, 
ftapi::FtMotorSpeed const&)'
/tmp/ccbRjnRM.o(.text+0x106): In function `MotorDraad(void*)':
: undefined reference to 
`ftapi::IfOutputs::setMotorSpeed(ftapi::ft_module_type, ftapi::ft_motor, 
ftapi::FtMotorSpeed const&)'
/tmp/ccbRjnRM.o(.text+0x663): In function 
`__static_initialization_and_destruction_0(int, int)':
: undefined reference to `ftapi::IfOutputs::IfOutputs[in-charge]()'
/tmp/ccbRjnRM.o(.text+0x682): In function 
`__static_initialization_and_destruction_0(int, int)':
: undefined reference to `ftapi::IfInputs::IfInputs[in-charge]()'
collect2: ld returned 1 exit status

If I'm using the wrong way for passing an int to a thread, please tell 
me or direct me to a link where I can find out how to do it.

Thank you for helping me out.

Huub

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