11e9
Subj : Re: passing an 'int' to a thread
To   : comp.programming.threads
From : doug
Date : Wed Jun 08 2005 05:43 pm


"doug" <noone@nowhere.co.uk> wrote in message 
news:t7ype.16027$bl3.8901@fe1.news.blueyonder.co.uk...
>
> Damn, I forgot the DGCs!
>
> "doug" <noone@nowhere.co.uk> wrote in message 
> news:n2ype.238581$Cq2.10303@fe2.news.blueyonder.co.uk...
>> Look for DGC below.
>>
>> "Huub" <hdotvdotniekerkathccnetdotnl> wrote in message 
>> news:42a671a3$0$156$3a628fcd@reader2.nntp.hccnet.nl...
>>> You were right. The errors were due to a linking problem. And I made a 
>>> another mistake which I corrected. Now something is being passed, but 
>>> it's not the correct value. Could you tell me what is being passed: 
>>> task_ids or t?
>>>
>>> New code:
>>>
>>>
>>> #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 = task_id
>>>     FtMotorSpeed mSpeed1(task_id);
>>>     cout << "Snelheid1 = " << task_id << endl;
>>>   // Initialspeed = task_id
>>>     FtMotorSpeed mSpeed2(task_id);
>>>     cout << "Snelheid2 = " << task_id << endl;
>>>   // 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));
>>
>
> DGC
>
>> You should be malloc'ing sizeof(int*) here.

IGNORE me here.  First thing in the morning, and all.

>>
>>>   *task_ids[t] = t;
>>>   while (snelheid != 8)
>>>     {
>>>       cin >> snelheid;
>>>       cout << "Aanmaken thread" << endl;
>>>       cout << "t = " << t << endl;
>>>       t = snelheid; // new piece of code
>>
>
> DGC
>
>> Here you assign a new value to t...
>>
>>>       rc = pthread_create(&threads[t], NULL, MotorDraad,
>>>   (void *)task_ids[t]);
>>> //what is passed: task_ids or t?
>>
>
> DGC
>
>> Tha value passed is task_ids[t], which is an int pointer.  However, just 
>> above you assigned a new value to t, so you likely haven't set up 
>> task_ids[t].  So you're probably passing an uninitialised, unless you can 
>> guarantee that t is always zero.  (In which case, why are you reading it 
>> from cin [via snelheid]?)
>>
>>>     }
>>>   pthread_exit(NULL);
>>>   return EXIT_SUCCESS;
>>> }
>>>
>>> // EOF
>>>
>>> Thank you for helping out.
>>
>> Hope that helps.  Not sure, though.
>>
>
>
>

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