Error: main.cpp: warning: using directive refers to implicitly-defined namespace ‘std’

If you see the following error when trying to compile a C++ application:

main.cpp: : : warning: using directive refers to implicitly-defined namespace 'std'

then that means you do not have any header file inclusion that uses std namespace.

You can fix this warning by including a C++ header file that uses a std namespace otherwise the compile will not know about std namespace.

Example: Implement a Stack of Strings in C++

Next example show how to implement a class of strings in C++. We will first read a text from a file and we will store it into a C++ string. Then we will split the string into words (by spaces) and we will store the words in a vector of strings.

Then we will iterate through that vector of strings and we will add elements our stack only if element not equal with “-“. If element is equal with “-” character then we will pop element from top of stack. We will display elements that we remove (using pop()) from our stack.

Class ReadFromFile

Class ReadFromFile header file (ReadFromFile.h):

#include <iostream>
#include <fstream>
 
using namespace std;
 
class ReadFromFile {
private:
    string fileName;
    long long buffLength;
    string buff;
 
public:
    ReadFromFile(string file);
    ~ReadFromFile();
 
    string displayBuffer();
    long long getFileLength();
};
</fstream></iostream>

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no matching function for call to ‘glutinit’

If you get this error in Xcode:

no matching function for call to ‘glutinit’

when you are trying to write a simple program with Glut a quick fix is to remove “const” from:

int main(int argc, const char * argv[])

C Plus Plus Error: undefined reference to `std::basic_string, std::allocator >::basic_string()’

Score.cc:(.text+0x11): undefined reference to `std::basic_string, std::allocator >::basic_string()’
Score.cc:(.text+0x2a): undefined reference to `std::string::operator=(char const*)’
Score.cc:(.text+0x5d): undefined reference to `std::basic_string, std::allocator >::~basic_string()’
Score.cc:(.text+0x82): undefined reference to `std::terminate()’
/tmp/Score-AOj1oH.o: In function `Score::~Score()':
Score.cc:(.text+0xb1): undefined reference to `std::basic_string, std::allocator >::~basic_string()’
/tmp/Score-AOj1oH.o: In function `Score::GetPlayerName()':
Score.cc:(.text+0xe8): undefined reference to `std::basic_string, std::allocator >::basic_string(std::string const&)’
/tmp/Score-AOj1oH.o:(.eh_frame+0x13): undefined reference to `__gxx_personality_v0′
clang: error: linker command failed with exit code 1 (use -v to see invocation)

To solve this error compile using -lstdc++ option (which links to stdc++ library):

clang -lstdc++ Score.cc main.cc

or:

g++ -lstdc++ Score.cc main.cc