Eclipse c++11 // vector

Question

This is really driving me crazy:

#include <iostream>
#include <vector>
#include <string.h>
#include <thread>

using namespace std;

void test() {
    vector<string> myvector;
    string a("Teststring");
    myvector.push_back(a);
    cout << myvector.begin()->length() << endl;
}

int main() {
    thread(test).join();
    return 0;
}

The code compiles fine with the -std=c++11 flag to the compiler and the -pthread flag to the linker.

BUT: Eclipse does either know the std::thread or the myvector.begin()->length(), even if the code runs fine eclipse warns me "Method 'length' could not be resolved".

I tried every possible solution in here: Eclipse CDT C++11/C++0x support without any success. This took me so many hours now, what am I doing wrong?!

Is there anybody getting a project setup without problems with this code?

EDIT: Other code example - same problem:

#include <iostream>
#include <vector>
#include <thread>


using namespace std;

class TestClass {
public:
    void test() {
        cout << "test" << endl;
    }
};

void test() {
    vector<TestClass> testClassVector;
    TestClass x;
    testClassVector.push_back(x);
    testClassVector.begin()->test();
}

int main() {
    thread(test).join();

    return 0;
}

Compiles and runs correct, but returns in eclipse: Method 'test' could not be resolved

EDIT:

working versions:

((TestClass)*(testClassVector.begin())).test();

TestClass foo2 = *(testClassVector.begin());
    foo2.test();

still not working:

testClassVector.begin()->test();

The last compiles and works like the two above, but eclipse still claims:

Method 'test' could not be resolved

Answer 1

The solution found:

I downloaded eclipse kepler Kepler

Created a new project and tried to compile this source code (like above):

#include <iostream>
#include <vector>
#include <thread>

using namespace std;

class TestClass {
public:
    void test() {
        cout << "test" << endl;
    }
};

void test() {
    vector<TestClass> testClassVector;
    TestClass x;
    testClassVector.push_back(x);
    testClassVector.begin()->test();
}

int main() {
    thread(test).join();
    return 0;
}

On the first run eclipse told me, thread belongs to the new c++11 standard and I have to add -std=c++11 to the compiler flags. To use thread I also added -pthread to the linker flags. With this steps the code could be compiled, but eclipse marks the thread still as unknown. To fix this I proceeded the following step:

Under C/C++ Build (at project settings), find the Preprocessor Include Path and go to the Providers Tab. Deselect all except CDT GCC Builtin Compiler Settings. Then untag Share settings entries … . Add the option -std=c++11 to the text box called Command to get compiler specs.

Found here.

Now - unbelievable but true - it works, even without any errors marked by eclipse. The solution is using the (beta) version of eclipse, wich seems to handle this in a better way.

Thanks for all your help!

Answer 2

I don't have Eclipse set up but the problem appears to be around std::string. Does the problem go away if you remove the threading from the example? (I also changed to #include <string> instead of string.h)

#include <iostream>
#include <vector>
#include <string>
#include <thread>

using namespace std;

#if 0
void test() {
    vector<string> myvector;
    string a("Teststring");
    myvector.push_back(a);
    cout << myvector.begin()->length() << endl;
}
#endif

int main() {
    //thread(test).join();
    vector<string> myvector;
    string a("Teststring");
    myvector.push_back(a);
    cout << myvector.begin()->length() << endl;
    return 0;
}

That should hopefully print out 10.

Update from comment:

Does this generate the Eclipse warning?

auto tmp = *(myvector.begin());
std::cout << tmp.length() << std::endl;

What about this?

std::string foo("abc123");
std::cout << foo.length() << std::endl;

I guess one more too:

std::string foo2 = *(myvector.begin());
std::cout << foo2.length() << std::endl;

Answer 3

Maybe I'm wrong, but I think your problem don't come from Eclypse. Juste, begin() on a vector return a std::vector<T>::iterator first, this is not a pointer and there is no method length, but you can ask for the vector size with myvector.size(); if this is what you want. The problem could come from your #include <string.h> that is not the same as #include <string>, string.h is for string operation like strcmp, strstr, etc... juste string will define the std::string object.