undefined-reference

I'm using Linux and I have the following files: main.c, main.h fileA.c, fileA.h fileB.cpp, fileB.h The function F1() is declared in fileB.h and defined in fileB.cpp . I need to use the function in fileA.c , and so I declared the function as extern void F1(); in fileA.c . However, during compilation, I got the error fileA.c: (.text+0x2b7): undefined reference to `F1' What is wrong? Thank you. ETA: Thanks to the answers I've received, I now have the following: In fileA.h, I have #include fileB.h #include main.h #ifdef __cplusplus extern "C" #endif void F1(); In fileA.c, I have #include fileA.h

This question already has an answer here: What does the “undefined reference to varName” in C mean? 6 answers I have this following simple program I am trying to compile in linux ubuntu. Main.c : #include <stdio.h> #include "Person.h" int main() { struct Person1 p1 = Person1_Constructor(10, 1000); } Person.c : #include <stdio.h> #include "Person.h" struct Person1 Person1_Constructor(const int age, const int salary) { struct Person1 p; p.age = age; p.salary = salary; return p; }; Person.h : struct Person1 { int age, salary; }; struct Person1 Person1_Constructor(const int age, const int salary);

I have a problem with compiling my program which uses glfw3 library. I'm getting list of errors of undefined references when trying to compile with make but my classes are compiled into .o files, only final executable file is not created. stdout: g++ -Wall -g -c main.cpp -lGL -lGLU -lglfw3 -lX11 -lXxf86vm -lXrandr -lpthread -lXi g++ -Wall -g -c error.cpp -lGL -lGLU -lglfw3 -lX11 -lXxf86vm -lXrandr -lpthread -lXi g++ -Wall -g -c sWindow.cpp -lGL -lGLU -lglfw3 -lX11 -lXxf86vm -lXrandr -lpthread -lXi g++ -Wall -g -o ecl main.o error.o sWindow.o -lGL -lGLU -lglfw3 -lX11 -lXxf86vm -lXrandr

The first couple are too long to reference. I get this error when I try to compile clang++ -stdlib=libc++ ../main.cc ... with clang and libc++ from the SVN. error: undefined reference to 'typeinfo for char const*' error: undefined reference to '__cxa_allocate_exception' error: undefined reference to '__cxa_throw' /tmp/cc-pbn00y.o:../main.cc:function std::__1::deque<double, std::__1::allocator<double> >::__add_back_capacity(): error: undefined reference to '__cxa_begin_catch' /tmp/cc-pbn00y.o:../main.cc:function std::__1::deque<double, std::__1::allocator<double> >::__add_back_capacity(): error

I'm not too familiar with c++ and how instantiating objects work, so this is probably a very simple thing to solve. When I compile with g++ I get the error " undefined reference to 'Foo::Foo(std::string)' ". I want to create an instance of the class Foo that has a string parameter in its constructor. Here is the code: Foo.h #include <string> using namespace std; class Foo { public: Foo(string s); private: string id; }; Foo.cpp #include <string> #include "Foo.h" using namespace std; Foo::Foo(string s) { id = s; } main.cpp #include <string> #include "Foo.h" using namespace std; int main() { Foo

After looking around for various sound API libraries, I have decided to use FMOD for the time being. Problem is that whenever I try to compile one of the code examples, I get the following errors: obj\Release\main.o:main.cpp|| undefined reference to `FMOD::System::getVersion(unsigned int*)@8'| obj\Release\main.o:main.cpp|| undefined reference to `FMOD::System::init(int, unsigned int, void*)@16'| obj\Release\main.o:main.cpp|| undefined reference to `FMOD::System::createSound(char const*, unsigned int, FMOD_CREATESOUNDEXINFO*, FMOD::Sound**)@20'| obj\Release\main.o:main.cpp|| undefined reference

Premise I’m using a C library (from C++) which provides the following interface: void register_callback(void* f, void* data); void invoke_callback(); Problem Now, I need to register a function template as a callback and this is causing me problems. Consider the following code: template <typename T> void my_callback(void* data) { … } int main() { int ft = 42; register_callback(reinterpret_cast<void*>(&my_callback<int>), &ft); invoke_callback(); } This gives me the following linker error (using g++ (GCC) 4.5.1 on OS X but works on most other combinations of compiler version / platform ):