CMake: fail import external library - reference

Question

I've this error that I receive when I try to compile:
Linking CXX executable /home/atv/catkin_ws/devel/lib/atvAcrosser/main**
CMakeFiles/main.dir/src/sendToCAN.cpp.o: In function `sendCAN()':
sendToCAN.cpp:(.text+0x432): undefined reference to `sendCanMessage(CanMsg*)'
collect2: ld returned 1 exit status
make[2]: *** [/home/atv/catkin_ws/devel/lib/atvAcrosser/main] Error 1
make[1]: *** [atvAcrosser/CMakeFiles/main.dir/all] Error 2
make: *** [all] Error 2
Invoking "make" failed
Main call the thread sendCAN [inside sendToCAN.cpp] who calls the function sendCanMessage in the external library libARV6005.a.
This is the CMakeList.txt:
include_directories(include ${catkin_INCLUDE_DIRS})
LINK_DIRECTORIES(${CMAKE_SOURCE_DIR}/atvAcrosser/lib/)
add_executable(main src/main.cpp src/setupPacketProtocol.cpp src/sendToCAN.cpp)
target_link_libraries(main ${catkin_LIBRARIES} ARV6005)
This is the tree:
src
├── atvAcrosser
│   ├── CMakeLists.txt
│   ├── include
│   │   └── atvAcrosser
│   │   ├── ARV6005Lib.h
│   │   ├── localPlannerCommunication.h
│   │   ├── receiveFromCAN.h
│   │   └── setupPacketProtocol.h
│   ├── lib
│   │   └── libARV6005.a
│   ├── package.xml
│   ├── src
│   │   ├── localPlannerCommunication.cpp
│   │   ├── main.cpp
│   │   ├── sendToCAN.cpp
│   │   ├── setupPacketProtocol.cpp
sendToCAN.h
// included dependencies
#include "ARV6005Lib.h"
//=================================
// function
void sendCAN();
sendToCAN.cpp
#include "../include/atvAcrosser/sendToCAN.h"
...
void sendCAN()
{
struct CanMsg msg;
struct CanMsg msg;
int i, result;
memset((void *)&msg, 0, sizeof msg);
msg.id = 0x33;
msg.id_type = STD_ID;
msg.length = 8;
for(i=0; i<8; i++) {
msg.data[i] = i;
}
result = sendCanMessage(&msg);
}
but with this Makefile in a tutorial example it works
all: main.c
gcc -w -o TestUtility -D_REENTRANT -I../Library -pthread ./main.c ./libARV6005.a

Answer 1

Check that sendCanMessage(CanMsg*) is declared in ARV6005Lib.h
Check that libARV6005.a contains symbol sendCanMessage
If symbol sendCanMessage is not in libARV6005.a, find where it is and link your executable with it.
Run make VERBOSE=1, extract link command and post it here
In your CMakeLists.txt you are missing _REENTRANT and pthread. Use target_compile_definitions and target_link_libraries to add it.

Answer 2

The ARV6005Lib.a was written in C.
The sendToCAN.cpp has been written in Cpp.
So was sufficient
edit the file that include ARV6005Lib.h:
extern "C" {
#include "../include/atvAcrosser/ARV6005Lib.h"
}