g++ complains about undefined reference even though library is included - c++

Question

I have a sample file like so, lets call it dnn_mmod_face_detection_ex.cpp
#include <iostream>
#include <dlib/dnn.h>
#include <dlib/data_io.h>
#include <dlib/image_processing.h>
#include <dlib/gui_widgets.h>
using namespace std;
using namespace dlib;
// ----------------------------------------------------------------------------------------
template <long num_filters, typename SUBNET> using con5d = con<num_filters,5,5,2,2,SUBNET>;
template <long num_filters, typename SUBNET> using con5 = con<num_filters,5,5,1,1,SUBNET>;
template <typename SUBNET> using downsampler = relu<affine<con5d<32, relu<affine<con5d<32, relu<affine<con5d<16,SUBNET>>>>>>>>>;
template <typename SUBNET> using rcon5 = relu<affine<con5<45,SUBNET>>>;
using net_type = loss_mmod<con<1,9,9,1,1,rcon5<rcon5<rcon5<downsampler<input_rgb_image_pyramid<pyramid_down<6>>>>>>>>;
// ----------------------------------------------------------------------------------------
int main(int argc, char** argv) try
{
if (argc == 1)
{
cout << "Call this program like this:" << endl;
cout << "./dnn_mmod_face_detection_ex mmod_human_face_detector.dat faces/*.jpg" << endl;
cout << "\nYou can get the mmod_human_face_detector.dat file from:\n";
cout << "http://dlib.net/files/mmod_human_face_detector.dat.bz2" << endl;
return 0;
}
net_type net;
deserialize(argv[1]) >> net;
image_window win;
for (int i = 2; i < argc; ++i)
{
matrix<rgb_pixel> img;
load_image(img, argv[i]);
// Upsampling the image will allow us to detect smaller faces but will cause the
// program to use more RAM and run longer.
while(img.size() < 1800*1800)
pyramid_up(img);
// Note that you can process a bunch of images in a std::vector at once and it runs
// much faster, since this will form mini-batches of images and therefore get
// better parallelism out of your GPU hardware. However, all the images must be
// the same size. To avoid this requirement on images being the same size we
// process them individually in this example.
auto dets = net(img);
win.clear_overlay();
win.set_image(img);
for (auto&& d : dets)
win.add_overlay(d);
cout << "Hit enter to process the next image." << endl;
cin.get();
}
}
catch(std::exception& e)
{
cout << e.what() << endl;
}
I have a Makefile like so
CC=g++
CFLAGS=-c -Wall -std=c++11 -v
LDFLAGS=-L/usr/local/cuda/lib64 -ldlib -lcudnn -lpthread -ldl -lrt -lX11 -lcublas -lcudnn -lcurand -lcusolver -lstdc++ -lm -lgcc_s -lc -lxcb -lXau -lXdmcp
SOURCES=dnn_mmod_face_detection_ex.cpp
OBJECTS=$(SOURCES:.cpp=.o)
EXECUTABLE=dnn_mmod_face_detection_ex
INCLUDE=
all: $(SOURCES) $(EXECUTABLE)
$(EXECUTABLE): $(OBJECTS)
$(CC) $(LDFLAGS) $(OBJECTS) -o $#
.cpp.o:
$(CC) $(CFLAGS) $(INCLUDE) $< -o $#
But I get undefined references to almost every dlib library. ie
dnn_mmod_face_detection_ex.cpp:(.text+0x267): undefined reference to `dlib::image_window::image_window()'
dnn_mmod_face_detection_ex.cpp:(.text._ZNK4dlib8gpu_data4hostEv[_ZNK4dlib8gpu_data4hostEv]+0x14): undefined reference to `dlib::gpu_data::copy_to_host() const'
dnn_mmod_face_detection_ex.cpp:(.text._ZN4dlib16resizable_tensorC2Ev[_ZN4dlib16resizable_tensorC5Ev]+0x31): undefined reference to `dlib::cuda::tensor_descriptor::tensor_descriptor()'
I know the following
This same example is compiled and is runs inside the /dlib/build/test... directory (dlib-19.9)
Those LDFLAGS I obtained by issuing the command ldd /dlib/build/test.../dnn_mmod_face_detection_ex
What is the right way to figure out what libraries are missing? I tried tracing the Cmake file(s) that dlib provided but it is more complicated than a particle accelerator.

Answer 1

It was a simple mistake of misplacing the LDFLAGS. It works when placed at the end like so
$(EXECUTABLE): $(OBJECTS)
$(CC) $(OBJECTS) -o $# $(LDFLAGS)