Boost filesystem incompatible with c++11 threads - c++

Question

I've had a maddening problem that I need some help with. I'm attempting to write a file finder or parser that finds all of the files of a given format in a directory. I want this to be a class, and I also want it to run in it's own separate thread from main(). I am using Ubuntu 14.04LTS, with it's boost installation (1.54). Here is the vanilla version of my code, just linking against boost::system.
#include <iostream>
#include <thread>
#include <vector>
#include <string>
class fileFinder {
private:
std::string dName;
public:
fileFinder() : dName("") { };
fileFinder(const std::string &dirName) : dName(dirName) { };
void runFileFinder(void) {
std::string fileFinderName = "Hi from filefinder!";
std::cout << fileFinderName << std::endl;
};
};
int main(int argc, char *argv[]) {
//Get the dirname, not safe yet
std::string dirName = argv[1];
fileFinder fFinderThread(dirName);
std::thread t1(&fileFinder::runFileFinder, &fFinderThread);
t1.join();
return EXIT_SUCCESS;
}
When I compile, everything works out great, and the class gets instantiated, and then run in a separate thread. I will link against boost_system just to show that everything is still ok.
> g++ -g -Wall -I/usr/include/boost/ -c rFileFinder.cpp -std=c++11 -pthread
> g++ -g -Wall rFileFinder.o -o rFileFinder -L/usr/lib/x86_64-linux-gnu/ -lboost_system -std=c++11 -pthread
> ./rFileFinder abcd
Hi from filefinder: abcd
Now, since I want to find all the files of a certain type, using boost::filesystem would be awesome. Even attempting to link against the boost::filesystem library produces a runtime threading error (just add -lboost_filesystem to the libraries).
> g++ -g -Wall -I/usr/include/boost/ -c rFileFinder.cpp -std=c++11 -pthread
> g++ -g -Wall rFileFinder.o -o rFileFinder -L/usr/lib/x86_64-linux-gnu/ -lboost_system -lboost_filesystem -std=c++11 -pthread
> ./rFileFinder abcd
terminate called after throwing an instance of 'std::system_error'
what(): Enable multithreading to use std::thread. Operation not permitted
Aborted (core dumped)
And so, this is driving me insane, since I am going to need to have both multithreading capabilities (there is a lot more than just this part of the problem). I've attempted to tease this answer out of the internet, but basically everything I come across is about how the linking to c++11 or pthread isn't done correctly in the compilation and linker steps. Is there a way for me to use both std::thread and boost::filesystem, or am I just hosed?

Answer 1

You need to link to the posix threads library on your system
With gcc or clang, typically this is done by supplying g++ -pthread on the command line.
Technically you should specify to link with the respective dynamic library too
g++ -pthread test.cpp -lboost_system -lboost_thread -lboost_filesystem

Answer 2

Using g++ 4.8, it seems that one cannot have both the -pthread and -std=c++11 flags for the compiler options. They mutually exclude each other on mac (with homebrew gcc48) and on my Ubuntu distro (14.04LTS with g++-4.8). Just use -std=c++11.