g++ ld: symbol(s) not found for architecture x86_64 - c++

Question

I'm trying to compile the Sam Hare's Struck code.
I'm using mac OSX10.9, opencv 2.4.6 and Eigen 2.0.17.
Eigen and opencv headers are stored in /opt/local/include while opencv dylib in /opt/local/lib.
I modified the Hare's Makefile to work on this folder. When I type make on the terminal:
g++ -L/opt/local/lib -lopencv_core -lopencv_highgui -lopencv_imgproc src/Config.o src/Features.o src/HaarFeature.o src/HaarFeatures.o src/HistogramFeatures.o src/ImageRep.o src/LaRank.o src/MultiFeatures.o src/RawFeatures.o src/Sampler.o src/Tracker.o src/main.o src/GraphUtils/GraphUtils.o -o struck
I get these errors:
Undefined symbols for architecture x86_64:
"cv::namedWindow(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&,
int)", referenced from:
_main in main.o "cv::split(cv::Mat const&, std::__1::vector<cv::Mat, std::__1::allocator<cv::Mat> >&)",
referenced from:
ImageRep::ImageRep(cv::Mat const&, bool, bool, bool) in ImageRep.o "cv::imread(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&,
int)", referenced from:
_main in main.o "cv::imshow(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&,
cv::_InputArray const&)", referenced from:
LaRank::Debug() in LaRank.o
Tracker::Debug() in Tracker.o
_main in main.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see
invocation)
Any ideas? Thanks!

Answer 1

I had a similar warning/error/failure when I was simply trying to make an executable from two different object files (main.o and add.o). I was using the command:
gcc -o exec main.o add.o
But my program is a C++ program. Using the g++ compiler solved my issue:
g++ -o exec main.o add.o
I was always under the impression that gcc could figure these things out on its own. Apparently not. I hope this helps someone else searching for this error.

Answer 2

finally solved my problem.
I created a new project in XCode with the sources and changed the C++ Standard Library from the default libc++ to libstdc++ as in this and this.

Answer 3

I am getting the same error. I don't think it is a "fix", but my work-around is to also include the cpp file. So instead of just putting
#include "MyClass.h"
I have to put
#include "MyClass.h"
#include "MyClass.cpp"

Answer 4

I wrote my declarition in the .h file
class String
{
String (const char * cstr = 0);
};
and I used inline in another .cpp file (implementation)
inline String::String(const char * cstr)
{
//code ...
}
then I use g++ and get this:
Undefined symbols for architecture x86_64:
"String::String(char const*)", referenced from:
_main in test-d389f3.o
ld: symbol(s) not found for architecture x86_64
solution: do not write inline when declarition and implementation is independent.

Answer 5

When I using clang to compile a C++ program, I have the similar error.
But after I changing to use chang++, the compilation worked.