Question

I’m using MinGw on Windows 7. The following simple program compiles fine, but the linker complains and I do not understand what’s wrong:

#include <iostream>   
#include <vector>

using namespace std;

int main()
{
   std::vector<int> iv;
   iv.push_back(7);
   cout << iv.back() << endl;
   return 0;
}

the compiler/linker messages look as follows:

mingw32-g++.exe -Wall -fexceptions  -std=c++0x -Wall -g  -std=c++0x -Wall -g -frepo   -IC:\cppbuchincludes\include -IG:\Boost -IG:\Users\thomas\cpp\STLUsage\\include  -c G:\Users\thomas\cpp\STLUsage\main.cpp -o obj\Debug\main.o
mingw32-g++.exe  -o bin\Debug\STLUsage.exe obj\Debug\main.o    G:\Boost\stage\lib\libboost_filesystem-mgw45-mt-d-1_45.dll.a G:\Boost\stage\lib\libboost_regex-mgw45-mt-d-1_45.dll.a G:\Boost\stage\lib\libboost_system-mgw45-mt-d-1_45.dll.a G:\Boost\stage\lib\libboost_thread-mgw45-mt-1_45.dll.a G:\Boost\stage\lib\libboost_unit_test_framework-mgw45-mt-d-1_45.dll.a
collect: recompiling G:\Users\thomas\cpp\STLUsage\main.cpp
collect: relinking
collect2: '_ZNSt12_Vector_baseIiSaIiEEC1Ev' was assigned to 'obj\Debug\main.rpo', but was not defined during recompilation, or vice versa
obj\Debug\main.o: In function `vector':
c:/mingw/bin/../lib/gcc/mingw32/4.5.2/include/c++/bits/stl_vector.h:208: undefined reference to `std::_Vector_base<int, std::allocator<int> >::_Vector_base()'
(...and so on...)

I can use templates I defined myself.

I have that MinGw binary from a book and followed the instructions in that book regarding compiler settings. In particular the references to the Boost libs are taken from there.

This must be a simple thing, I just want to make trivial use of the STL.

Edit following the advice given in an answer, I replaced the binary to be used to compile by g++.exe in the Settings -> Compiler and debugging -> toolchain executables dialog, but I’m getting the same error messages (with mingw32-g++.exe now replaced by g++.exe).

Edit (once more) this has to be problem eith the Code::Blocks settings, since compiling using g++ from the command line works just fine.

Answer 1

Use g++ to compile and link the program. mingw32-g++.exe doesn’t do that.

FAQ says,

What’s the difference between gcc and mingw32-gcc?

The mingw32-gcc, mingw32-g++, etc. binaries exist as an aid to cross development. They are created in a typical build of gcc. They are therefore distributed as the maintainers of GCC meant them to be. The gcc.exe indicates that the binary produces binaries for a target equal to the build, while the mingw32-gcc binary produces binaries to be executed on the mingw32 target.

So I guess the problem is because of mingw32-g++.exe which you’re not supposed to use, for normal build.

Try these:

g++ program.cpp              //simple build

g++ program.cpp  -Wall       //build with all warnings enabled

g++ program.cpp  -Wall -O2   //enable warnings and optimization level 2

g++ program.cpp -std=c++0x   //use C++11 features

Hope that helps.