Cmake: undefined reference to included methods - c++

Question

I am learning to use cmake and I am trying to compile a simple set of tests using gtest for a very small project that I wrote.
my CMakeLists.txt looks like
cmake_minimum_required(VERSION 2.6)
project(circuit_sim)
include(FetchContent)
FetchContent_Declare(
googletest
# Specify the commit you depend on and update it regularly.
URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
add_executable(test Connector.cpp test.cpp)
target_link_libraries(test gtest_main)
I got most of it from the googletest docs. I am trying to compile an executable that has a main() in test.cpp and relies on a Connector class in Connector.cpp and Connector.h. All files are in the same directory
when I run cmake . and then make I get the following error:
/usr/bin/ld: CMakeFiles/test.dir/test.cpp.o: in function `AllTests_CircuitTest_Test::TestBody()':
test.cpp:(.text+0x33): undefined reference to `Connector::Connector()'
/usr/bin/ld: test.cpp:(.text+0x4c): undefined reference to `Connector::Connector()'
/usr/bin/ld: test.cpp:(.text+0x6d): undefined reference to `Connector::Connector(Connector*)'
/usr/bin/ld: test.cpp:(.text+0x7d): undefined reference to `Connector::connect(Connector*)'
/usr/bin/ld: test.cpp:(.text+0x93): undefined reference to `Connector::in(unsigned long, unsigned long)'
/usr/bin/ld: test.cpp:(.text+0xb8): undefined reference to `Connector::out()'
/usr/bin/ld: test.cpp:(.text+0xc4): undefined reference to `Connector::get_out_conn()'
/usr/bin/ld: test.cpp:(.text+0xd6): undefined reference to `Connector::get_v()'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/test.dir/build.make:86: test] Error 1
make[1]: *** [CMakeFiles/Makefile2:139: CMakeFiles/test.dir/all] Error 2
make: *** [Makefile:130: all] Error 2
It seems that cmake did not know to include Connector.cpp in the compilation even though I specified it in the CMakeLists.txt. What am I doing wrong?
Code for Connector.cpp, currently it doesn't do very much lol but it's a wip
#include "Connector.h"
#include "circuit_utils.h"
Connector::Connector(){
this->v = 0;
this->c = 0;
this->out_conn = nullptr;
}
Connector::Connector(Connector* out_conn){
this->v = 0;
this->c = 0;
this->out_conn = out_conn;
}
Connector* Connector::connect(Connector* out_conn){
this->out_conn = out_conn;
return this;
}
Connector* Connector::in(uint64_t v, uint64_t c){
this->v = v;
this->c = c;
//this->out();
return this;
}
Connector* Connector::out(){
if(out_conn != nullptr)
out_conn->in(v, c);
return this;
}
uint64_t Connector::get_v() { return v; }
uint64_t Connector::get_c() { return c; }
Connector* Connector::get_out_conn() { return out_conn; }
std::string Connector::to_string() {
std::string to_return = "";
to_return += "-------------\n";
to_return += "voltage: " + std::to_string(FROM_MICROS(((double)v))) + " volts\n";
to_return += "current: " + std::to_string(FROM_MICROS(((double)c))) + " amps\n";
to_return += "-------------\n";
return to_return;
}
Code for test.cpp
#include <iostream>
#include <unistd.h>
#include "gtest/gtest.h"
#include "Connector.h"
#include "circuit_utils.h"
using namespace std;
TEST (AllTests, CircuitTest) {
Connector* power = new Connector();
Connector* ground = new Connector();
power->connect(new Connector(ground));
power->in(TO_MICROS(3.3), TO_MICROS(3.3));
Connector *cur_conn = power;
while(cur_conn != nullptr){
sleep(5);
cur_conn->out();
cur_conn = cur_conn->get_out_conn();
}
ASSERT_EQ(3.3, ground->get_v());
}

Answer 1

Since you need external class, you should put that class "library" in target_link_libraries(), so that the last line of your CMakeLists.txt will become
target_link_libraries(test connector gtest_main)
Also, in another CMakeLists.txt which is in the same directory as Connector.cpp, your should declare them as one library:
set(SOURCES Connector.cpp)
add_library(connector STATIC ${SOURCES})