Error when trying link jsoncpp and include it in a CUDA project: undefined reference to `Json::Value::Value(Json::ValueType)'

Question

When I try and #include "json/json.h" in a .cu file, then run make, I get the following error:

nvcc -o sound main.o process.o -L /usr/lib -lopencv_core -lopencv_imgproc -lopencv_highgui -O3 -arch=sm_20 -Xcompiler -Wall -Xcompiler -Wextra -m64

/usr/local/cuda/bin/crt/link.stub:90:13: warning: ‘void __cudaRegisterLinkedBinary(const __fatBinC_Wrapper_t*, void (*)(void**), void*)’ defined but not used [-Wunused-function]

process.o: In function `count_tracks()':

tmpxft_00006061_00000000-3_process.cudafe1.cpp:(.text+0x75): undefined reference to `Json::Value::Value(Json::ValueType)'

tmpxft_00006061_00000000-3_process.cudafe1.cpp:(.text+0x7d): undefined reference to `Json::Value::~Value()' collect2: ld returned 1 exit status make: *** [student] Error 1

in reference to when I try and create a Json::Value. I've tried moving around where I link JsonCpp library, and I wasn't having this problem #including jsoncpp and creating a Json::Value in the main.cpp of the project. It just doesn't seem to be working correctly when in a .cu file.

Here is the pertinent stuff from my Makefile, which I got from Udacity's CUDA course and modified to fit my needs:

NVCC=nvcc
CXX = g++
LDFLAGS = -L ~/parallelcomputing/soundcloud/jsoncpp/build/debug/lib -ljsoncpp
INC = -I ~/parallelcomputing/soundcloud/jsoncpp/include
OPENCV_LIBPATH=/usr/lib
OPENCV_INCLUDEPATH=/usr/include
OPENCV_LIBS=-lopencv_core -lopencv_imgproc -lopencv_highgui

CUDA_INCLUDEPATH=/usr/local/cuda/include

NVCC_OPTS=-O3 -arch=sm_20 -Xcompiler -Wall -Xcompiler -Wextra -m64

GCC_OPTS=-O3 -Wall -Wextra -m64

student: main.o process.o Makefile
    $(NVCC) -o sound main.o process.o -L $(OPENCV_LIBPATH) $(OPENCV_LIBS) $(NVCC_OPTS)

main.o: main.cpp
    g++ -c main.cpp $(GCC_OPTS) $(LDFLAGS) $(INC) -I $(CUDA_INCLUDEPATH) -I $(OPENCV_INCLUDEPATH)

process.o: process.cu
    nvcc -c process.cu $(NVCC_OPTS) $(LDFLAGS) $(INC)

clean:
    rm -f *.o *.png hw

Answer 1

You've got LDFLAGS defined in your makefile, but you're not using it in the link phase that I can see.

As a result, -ljsoncpp doesn't show up in the link command you posted, that is showing the error.

Add LDFLAGS to your link phase:

student: main.o process.o Makefile
      $(NVCC) -o sound main.o process.o $(LDFLAGS) -L $(OPENCV_LIBPATH) $(OPENCV_LIBS) $(NVCC_OPTS)

(And while we're cleaning up your makefile, LDFLAGS contains link specification, and is not relevant in, and can be safely deleted from, the subsequent compile targets.)

EDIT: Since that is not working, but you say the link is successful with a .cpp file, try linking the executable with g++ instead of nvcc:

LDFLAGS2=-L/usr/local/cuda/lib64 -lcudart

student: main.o process.o Makefile
      $(CXX) -o sound main.o process.o $(LDFLAGS) $(LDFLAGS2) -L $(OPENCV_LIBPATH) $(OPENCV_LIBS)