Opencv Undefined symbols for architecture cv:imwrite Mac osX high Sierra - c++

Question

I downloaded GCC and opencv(3.4.1_2) in my Mac OS X high Sierra(10.13.3) through homebrew.
$ g++ --version
g++-7 (Homebrew GCC 7.3.0_1) 7.3.0
In my "opencvtest.cpp", cv::imwrite was seen as undefined symbols for architecture but other functions such as cv::imread, cv::namedWindow worked perfectly.
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgcodecs.hpp"
#include <iostream>
using namespace cv;
int main( int argc, char** argv ) {
Mat img = imread( argv[1], -1 );
if( img.empty() ) return -1;
namedWindow( "Example1", cv::WINDOW_AUTOSIZE );
imshow( "Example1", img );
imwrite("Example1.jpg", img); //<-- error
waitKey( 0 );
destroyWindow( "Example1" );
}
Makefile was written as:
CC = g++
CFLAGS = -g -Wall -std=c++11
OPENCV = `pkg-config --cflags --libs opencv`
test: opencvtest.o
$(CC) -o $# opencvtest.o $(CFLAGS) $(OPENCV)
opencvtest.o: opencvtest.cpp
$(CC) -c opencvtest.cpp $(CFLAGS) $(OPENCV)
Compilation using g++ in terminal yielded:
In file included from /usr/local/Cellar/opencv/3.4.1_2/include/opencv2/core.hpp:54:0,
from /usr/local/Cellar/opencv/3.4.1_2/include/opencv2/highgui.hpp:46,
from /usr/local/Cellar/opencv/3.4.1_2/include/opencv2/highgui/highgui.hpp:48,
from opencvtest.cpp:2:
/usr/local/Cellar/opencv/3.4.1_2/include/opencv2/core/base.hpp:381:35: warning:unknown option after '#pragma GCC diagnostic' kind [-Wpragmas]
# pragma GCC diagnostic ignored "-Winvalid-noreturn"
^~~~~~~~~~~~~~~~~~~~
g++ -o test opencvtest.o -g -Wall -std=c++11 `pkg-config --cflags --libs opencv`
Undefined symbols for architecture x86_64:
"cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector<int, std::allocator<int> > const&)", referenced from:
_main in opencvtest.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make: *** [test] Error 1
If I commented the problematic imwrite("Example1.jpg", img);, the program worked perfectly and the image can be shown. I had reinstalled opencv3 for many times and this problem seemed to be unsolvable. Can any clever people tell me what should I do next?
Edit:Here is my opencv profile. It said that the default C++ compiler was clang++ but not g++-7.
$opencv_version -v
General configuration for OpenCV 3.4.1 =====================================
Version control: unknown
Extra modules:
Location (extra): /tmp/opencv-20180307-60086-ryy1b3/opencv-3.4.1/opencv_contrib/modules
Version control (extra): unknown
Platform:
Timestamp: 2018-03-07T08:15:55Z
Host: Darwin 17.3.0 x86_64
CMake: 3.10.2
CMake generator: Unix Makefiles
CMake build tool: /usr/local/Homebrew/Library/Homebrew/shims/super/gmake
Configuration: Release
CPU/HW features:
Baseline: SSE SSE2 SSE3
requested: SSE3
disabled: SSE4_1 SSE4_2 AVX AVX2
Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
SSE4_1 (3 files): + SSSE3 SSE4_1
SSE4_2 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2
FP16 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
AVX (5 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
AVX2 (9 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
AVX512_SKX (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_SKX
C/C++:
Built as dynamic libs?: YES
C++11: YES
C++ Compiler: /usr/local/Homebrew/Library/Homebrew/shims/super/clang++ (ver 9.0.0.9000039)
C++ flags (Release): -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -Wno-implicit-fallthrough -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -DNDEBUG -DNDEBUG
C++ flags (Debug): -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -Wno-implicit-fallthrough -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g -O0 -DDEBUG -D_DEBUG
C Compiler: /usr/local/Homebrew/Library/Homebrew/shims/super/clang
C flags (Release): -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -Wno-implicit-fallthrough -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -DNDEBUG -DNDEBUG
C flags (Debug): -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winit-self -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -Wno-implicit-fallthrough -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g -O0 -DDEBUG -D_DEBUG
Linker flags (Release):
Linker flags (Debug):
ccache: NO
Precompiled headers: NO
Extra dependencies: /usr/local/lib/libtbb.dylib
3rdparty dependencies:
OpenCV modules:
To be built: aruco bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dpm face features2d flann fuzzy hfs highgui img_hash imgcodecs imgproc java_bindings_generator line_descriptor ml objdetect optflow phase_unwrapping photo plot python2 python3 python_bindings_generator reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab xfeatures2d ximgproc xobjdetect xphoto
Disabled: js world
Disabled by dependency: -
Unavailable: cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv dnn_modern freetype hdf java matlab ovis sfm ts viz
Applications: apps
Documentation: NO
Non-free algorithms: YES
GUI:
Cocoa: YES
Media I/O:
ZLib: /usr/lib/libz.dylib (ver 1.2.11)
JPEG: build (ver 90)
WEBP: build (ver encoder: 0x020e)
PNG: /usr/local/lib/libpng.dylib (ver 1.6.34)
TIFF: /usr/local/lib/libtiff.dylib (ver 42 / 4.0.9)
OpenEXR: /usr/local/lib/libImath.dylib /usr/local/lib/libIlmImf.dylib /usr/local/lib/libIex.dylib /usr/local/lib/libHalf.dylib /usr/local/lib/libIlmThread.dylib (ver 2.2.0)
Video I/O:
FFMPEG: YES
avcodec: YES (ver 57.107.100)
avformat: YES (ver 57.83.100)
avutil: YES (ver 55.78.100)
swscale: YES (ver 4.8.100)
avresample: YES (ver 3.7.0)
AVFoundation: YES
Parallel framework: TBB (ver 2018.0 interface 10002)
Trace: YES (with Intel ITT)
Other third-party libraries:
Intel IPP: 2017.0.3 [2017.0.3]
at: /tmp/opencv-20180307-60086-ryy1b3/opencv-3.4.1/build/3rdparty/ippicv/ippicv_mac
Intel IPP IW: sources (2017.0.3)
at: /tmp/opencv-20180307-60086-ryy1b3/opencv-3.4.1/build/3rdparty/ippicv/ippiw_mac
Lapack: YES (/System/Library/Frameworks/Accelerate.framework /System/Library/Frameworks/Accelerate.framework)
Eigen: YES (ver 3.3.4)
Custom HAL: NO
Protobuf: build (3.5.1)
OpenCL: YES (no extra features)
Include path: NO
Link libraries: -framework OpenCL
Python 2:
Interpreter: /usr/local/opt/python#2/libexec/bin/python (ver 2.7.14)
Libraries: /usr/local/Cellar/python#2/2.7.14_1/Frameworks/Python.framework/Versions/2.7/lib/libpython2.7.dylib (ver 2.7.14)
numpy: /usr/local/lib/python2.7/site-packages/numpy/core/include (ver 1.14.1)
packages path: lib/python2.7/site-packages
Python 3:
Interpreter: /usr/local/opt/python/bin/python3 (ver 3.6.4)
Libraries: /usr/local/opt/python/Frameworks/Python.framework/Versions/3.6/lib/python3.6/config-3.6m-darwin/libpython3.6.dylib (ver 3.6.4)
numpy: /usr/local/lib/python3.6/site-packages/numpy/core/include (ver 1.14.1)
packages path: lib/python3.6/site-packages
Python (for build): /usr/local/opt/python#2/libexec/bin/python
Java:
ant: NO
JNI: /Library/Java/JavaVirtualMachines/jdk-9.0.1.jdk/Contents/Home/include /Library/Java/JavaVirtualMachines/jdk-9.0.1.jdk/Contents/Home/include/darwin /Library/Java/JavaVirtualMachines/jdk-9.0.1.jdk/Contents/Home/include
Java wrappers: NO
Java tests: NO
Matlab: NO
Install to: /usr/local/Cellar/opencv/3.4.1_2
-----------------------------------------------------------------
Thus one only used clang++ instead of g++ with or without CFLAG = -g and compilation worked well. I wondered if one can change opencv default compiler from clang++ to g++?

Answer 1

As I suggested in the comments, this is likely to work if you use the clang++ compiler in place of GNU g++, which is why I suggested you run:
opencv_version -v
If you look at the output, specifically the line that starts C++ Compiler: you can see that OpenCV was compiled with a derivative of clang++.
I have generally "just gone with flow" and used the same compiler as OpenCV was built with, but I guess there are other options.
I guess you could either:
force OpenCV to compile with g++, or
force g++ to compile your application such that it can link with OpenCV compiled with clang++.
I have tested the first suggestion above, namely compiling OpenCV with the GNU compiler and that works like this:
cmake -D CMAKE_CXX_COMPILER=/usr/local/bin/g++-7 -D CMAKE_C_COMPILER=/usr/local/bin/gcc-7 ...
make -j8
make install
I guess the latter is done with something like:
g++ YourApp.cpp -std=C++11 -stdlib=libstdc++ $(pkg-config ...) -o YourApp
But if anyone knows better, PLEASE COMMENT and I'll update the advice!

Answer 2

Almost is because not link the proper library. Find by yourself is difficult.
I solve that by
g++ HelloWorld.cpp -o hello `pkg-config --cflags --libs opencv`
My source file is HelloWorld.cpp, and you can run pkg-config --cflags --libs opencv alone. It just print the params about include header and link library:
$ pkg-config --cflags --libs opencv
-I/usr/local/include/opencv -I/usr/local/include -L/usr/local/lib -lopencv_dnn -lopencv_ml -lopencv_objdetect -lopencv_shape -lopencv_stitching -lopencv_superres -lopencv_videostab -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_imgproc -lopencv_flann -lopencv_core
My source file is
#include <iostream>
#include "opencv2/opencv.hpp"
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(0); // Wait for a keystroke in the window
return 0;
}
And i test the really problem by put params that pkg-config --cflags --libs opencv product one by one. Finally I find my problem is not set
-I/usr/local/include/opencv -I/usr/local/include
. That really killing me. I forget to set header directory......