程序使用 pkg-config --cflgas opencv 和 pkg-config --ldflag 编译正常，但不可执行（ubuntu 16.04）

Question

Recently I installed opencv on my ubuntu 16.04 machine(I've done this many times before and used it ok). I tried compiling yolo program, it compiled ok and ran ok. When I set OPENCV=1 in the Makefile, it compiles the program with opencv. To set the compile and link flags it has these two lines.

LDFLAGS+= `pkg-config --libs opencv` -lstdc++
COMMON+= `pkg-config --cflags opencv`

My pkg-config commands work correctly. See the output below.

ckim@chan-ubuntu:~/YOLOV2/darknet$ pkg-config --cflags opencv
-I/home/ckim/opencv_install/installation/OpenCV-3.4/include/opencv -I/home/ckim/opencv_install/installation/OpenCV-3.4/include
ckim@chan-ubuntu:~/YOLOV2/darknet$ pkg-config --libs opencv
-L/home/ckim/opencv_install/installation/OpenCV-3.4/lib -lopencv_stitching -lopencv_videostab -lopencv_superres -lopencv_surface_matching -lopencv_dnn_objdetect -lopencv_line_descriptor -lopencv_aruco -lopencv_img_hash -lopencv_xobjdetect -lopencv_dpm -lopencv_freetype -lopencv_stereo -lopencv_face -lopencv_objdetect -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_saliency -lopencv_hfs -lopencv_ccalib -lopencv_tracking -lopencv_datasets -lopencv_plot -lopencv_optflow -lopencv_ximgproc -lopencv_fuzzy -lopencv_bioinspired -lopencv_highgui -lopencv_videoio -lopencv_text -lopencv_dnn -lopencv_reg -lopencv_hdf -lopencv_bgsegm -lopencv_rgbd -lopencv_sfm -lopencv_xfeatures2d -lopencv_calib3d -lopencv_shape -lopencv_imgcodecs -lopencv_features2d -lopencv_video -lopencv_ml -lopencv_flann -lopencv_xphoto -lopencv_photo -lopencv_imgproc -lopencv_core

A couple of days ago, I tried compiling a simple opencv pgrogram that I find on a web page and tried compiling it. (Iwanted to test a basic display window's behavior). The program was like this. very typical)

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main( int argc, char** argv )
{
    if( argc != 2)
    {
     cout <<" Usage: display_image ImageToLoadAndDisplay" << endl;
     return -1;
    }

    Mat image;
    image = imread(argv[1], CV_LOAD_IMAGE_COLOR);   // Read the file

    if(! image.data )                              // Check for invalid input
    {
        cout <<  "Could not open or find the image" << std::endl ;
        return -1;
    }

    namedWindow( "Display window", WINDOW_AUTOSIZE );// Create a window for display.
    imshow( "Display window", image );                   // Show our image inside it.

    waitKey(1);                                          // Wait for a keystroke in the window
    return 0;
}

When I compile and link it with command

gcc -c test.cpp `pkg-config --cflags opencv` `pkg-config --libs opencv` -o test

it gives me no error and I see the file test but it's not executable. When I run it after setting chmod +x test , I get

ckim@chan-ubuntu:~/opencvtest$ ./test
bash: ./test: cannot execute binary file: Exec format error
ckim@chan-ubuntu:~/opencvtest$ file test
test: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped

What could be wrong?

Answer 1

As per the comment you're command line...

gcc -c test.cpp `pkg-config --cflags opencv` `pkg-config --libs opencv` -o test

includes the -c flag which tells the compiler to compile only -- don't link. Also. as you're code is c++ rather than c you need to link with the correct runtime libraries. That means using g++ rather than gcc . So the command should be...

g++ test.cpp `pkg-config --cflags opencv` `pkg-config --libs opencv` -o test