Boost Thread int parameter to member function not working?

Question

Completely new to threading and concurrency but I'm trying to start a function as a new thread and I don't understand my errors. I receive an error along the lines of Candidate expects X arguments, 2 provided. This error repeats for 0 < X <= 9 (except 2). However, in every example I've seen it's as simple as just putting your function and it's arguments. My code looks like:

Trainer.cpp:

int time = 5; // for example

void Member::decrement(int seconds){
    while(seconds > 0){
        seconds--;
        Sleep(1000);
    }
    isBusy = false;
}

void Member::startDecrement(string state){
    if (state == "busy"){ // isBusy is a private boolean, hence this
        isBusy = true;
        thread myThread = thread(decrement, time); // Thread for method
        myThread.join(); 
    else {
        isBusy = false;
    }
}

Yet this doesn't work? Can somebody give me guidance on this please, what I'm trying to do is quite simple but I have found no way that works for me as of yet. Alternatives to thread are appreciated too, I've seen that std::async is an option but that doesn't seem to work with my compiler setup.

Setup info: -sdt=c++11, MinGW, Win64, GCC 4.7.2

EDIT:

Seeing as I've been nailed for errors, here is the entire error log.

I've also tried the code provided in the answer, no luck.

You are likely to get better answers if you include a minimal but complete example and include the actual error message and not some approximation thereof. — NPE, Mar 02 '13 at 16:53
Isn't it possible that your argument named `time` actually refers to the standard `time()` function? What if you rename your `time` variable? — Andy Prowl, Mar 02 '13 at 16:56
@NPE That is a minimal but complete example, as that's what's causing the error. — whitfin, Mar 02 '13 at 16:57
@AndyProwl `time` is there for an example, the actual variable is a longer name of `transactionTime`. — whitfin, Mar 02 '13 at 16:58
@NPE Complete in the sense that you have enough to find out what the error is, yes. But fine, I shall amend it. — whitfin, Mar 02 '13 at 16:59
@Zackehh9lives: See your minimal example working [here](http://liveworkspace.org/code/3SpAkW$88) — Andy Prowl, Mar 02 '13 at 17:02
@AndyProwl My code has been filled, although I see no reason why the other operations involved should affect anything. — whitfin, Mar 02 '13 at 17:04
Bases on your error message, the part you should focus on is this: `cannot convert '((Trainer*)this)->Trainer::decrementTime' (type '') to type 'const attributes& {aka const boost::thread_attributes&}'` — JaredC, Mar 02 '13 at 17:26
@JaredC That makes sense, except I see no issues in the methods above when comparing them to examples which would cause that error to occur? — whitfin, Mar 02 '13 at 17:28
@Zackehh9lives Are the examples you're looking at for member functions as `decrementTime` is? The fact that you're having a problem indicates that you don't understand something (this is perfectly normal!!), but this is why we need a *complete* example, because sometimes we just aren't aware of what we are leaving out. — JaredC, Mar 02 '13 at 17:30
@JaredC I believed so, although perhaps not. Do you have such an example? — whitfin, Mar 02 '13 at 17:31

score 2 · Accepted Answer · answered Mar 02 '13 at 17:33

2

Since your compile errors seem to indicate that decrementTime is a member function, you need to provide an object to invoke it on (e.g. this pointer):

thread myThread = thread(&Trainer::decrementTime, this, transactionTime);

answered Mar 02 '13 at 17:33

JaredC

5,150
1
20
45

1

@Zackehh9lives No problem, I hope it makes sense why we needed a complete example (i.e. with `decrementTime` as a member function). Please read this: http://sscce.org/ – JaredC Mar 02 '13 at 17:37
It does now, yes. I had assumed there was no difference between the two (stupid, I know). – whitfin Mar 02 '13 at 17:38

score 0 · Answer 2 · answered Mar 02 '13 at 17:06

0

This is a minimal and complete example:

#include <iostream>
#include <thread>

void decrement(int seconds) {
  std::cout << "seconds: " << seconds << std::endl;
}
int main(int arg, char * argv[]) {
  int time = 100;
  std::thread myThread(decrement, time);
  myThread.join();
  return 0;
}

Compile it like this: g++ thread.cpp -o thread -std=c++11 -pthread

Next time, give such an example and also the complete error message and make sure not to have typos in the technical details such as compiler flags.

answered Mar 02 '13 at 17:06

DennisL

466
3
6

This is what I have been doing (see updated question). Also note I'm using `boost::thread` not `std::thread`. – whitfin Mar 02 '13 at 17:08
(+1) for showing there's nothing wrong with the code, and for demonstrating how the question should have been asked in the first place. – NPE Mar 02 '13 at 17:11
@Zackehh9lives: Apologies if this sounds harsh, but you still haven't given us enough information to even reproduce the problem, let alone solve it. – NPE Mar 02 '13 at 17:13
@NPE I don't understand what you want? That's the exact code I'm running, the rest of the code is entirely separate from the issue. – whitfin Mar 02 '13 at 17:14
To switch to boost, you simply change two lines `#include ` and `boost::thread myThread(decrement, time);` – DennisL Mar 02 '13 at 17:15
@Zackehh9lives: Exact code? With a variable named `bool`?! Seriously, please stop wasting everyone's time by making implausible claims. – NPE Mar 02 '13 at 17:15
@NPE Well, aside from variable names :p And if changing to boost just requires changing the two lines, why doesn't mine work as it is now? – whitfin Mar 02 '13 at 17:16
Show a little more effort: Have you tried the sample code from above and what's the exact error message you are getting? – DennisL Mar 02 '13 at 17:18

Boost Thread int parameter to member function not working?

2 Answers2