error: undefined reference to 'cv::imread(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'

[swansorter]

sir,
i cross compiled opencv 4.1.2 in my ubuntu pc (16.04) using cmake gui
in my cmake set windowi given
operating system arm-linux
processor arm
compilers:
c: /opt/FriendlyARM/toolchain/4.9.3/bin/arm-cortexa9-linux-gnueabihf-cc
c++: /opt/FriendlyARM/toolchain/4.9.3/bin/arm-cortexa9-linux-gnueabihf-c++
target /opt/FriendlyARM/toolchain/4.9.3/arm-cortexa9-linux-gnueabihf/sys-root
CMAKE _INSTALL_PRIFIX=usr/local/arm/openc-arm
after cross compilation

#-------------------------------------------------
#
# Project created by QtCreator 2021-03-09T14:11:00
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = opencv3
TEMPLATE = app
CONFIG += c++11
# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
INCLUDEPATH += /usr/local/arm/opencv-arm/include/opencv4 \
    ./resources

LIBS += -L/usr/local/arm/opencv-arm/lib -I/usr/local/arm/opencv-arm/include/opencv4 -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -lopencv_objdetect
SOURCES += \
        main.cpp \
        mainwindow.cpp

HEADERS += \
        mainwindow.h

FORMS += \
        mainwindow.ui
INSTALLS = target
target.files = opencv3
target.path = /home/pi

compilation output:-

16:50:30: Running steps for project opencv...
16:50:30: Configuration unchanged, skipping qmake step.
16:50:30: Starting: "/usr/bin/make"
arm-linux-gnueabihf-g++ -fuse-ld=gold -mfloat-abi=hard --sysroot=/opt/rootfs-s5p4418 -Wl,-rpath,/usr/local/Trolltech/Qt-5.10.0-nexell32/lib -o opencv3 main.o mainwindow.o moc_mainwindow.o -L/usr/nexell-libs/lib32 -L/usr/local/arm/opencv-arm/lib -I/usr/local/arm/opencv-arm/include/opencv4 -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -lopencv_objdetect -L/opt/rootfs-s5p4418/usr/local/Trolltech/Qt-5.10.0-nexell32/lib -lQt5Widgets -lQt5Gui -lQt5Core -lGLESv2 -lpthread
../opencv/mainwindow.cpp:22: error: undefined reference to 'cv::imread(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'
collect2: error: ld returned 1 exit status
Makefile:251: recipe for target 'opencv3' failed
make: *** [opencv3] Error 1

[jsulm]

@swansorter said in error: undefined reference to 'cv::imread(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)':

LIBS += -L/usr/local/arm/opencv-arm/lib -I/usr/local/arm/opencv-arm/include/opencv4 -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -lopencv_objdetect

What is this?! Why do you add include folder to the libs search paths?
What are the names of the libs inside /usr/local/arm/opencv-arm/lib?

[swansorter]

@jsulm
sorry it is
LIBS += -L/usr/local/arm/opencv-arm/lib -lopencv_core -lopencv_imgcodecs -lopencv_imgproc -lopencv_objdetect

[jsulm]

@swansorter Did you try full rebuild after fixing pro file?

[swansorter]

@jsulm yess sir same error

[swansorter]

@swansorter The m

[jsulm]

@swansorter Actually you should install the libs/headers in your sysroot

[swansorter]

@jsulm how to install the libs/headers in my sysroot

[jsulm]

@swansorter Simply copy them to your sysroot...

[swansorter]

@jsulm what i need to copy and in sysroot where i need to paste?

[jsulm]

@swansorter Libs to: /opt/rootfs-s5p4418/usr/lib
Include files to: /opt/rootfs-s5p4418/usr/include

[swansorter]

@jsulm
from : usr/local/arm/opencv-arm/libs To: /opt/rootfs-s5p4418/usr/lib
from : usr/local/arm/opencv-arm/include To: /opt/rootfs-s5p4418/usr/include
ist this write?

[jsulm]

@swansorter yes

[swansorter]

@jsulm i followed above steps still same error