This blog post is just a record of C + + compilation and installation problems – it doesn’t give the correct solution

main.cpp:(.text+0xd06): undefined reference to `uni_text::UniText::UniText(std::string const&, int)'
main.cpp:(.text+0xe73): undefined reference to `uni_text::UniText::PutText(cv::Mat&, std::string const&, cv::Point_<int> const&, cv::Scalar_<double> const&, bool)'

Analysis:
encounter this problem: run some C + + projects that contain special so dynamic library or static library;
the compiled versions of GCC and G + + used by the native environment are not completely consistent with the libraries (dynamic library or static library) compiled by the author, resulting in these errors

1: There is no corresponding dependency (static library or dynamic library). 2: the compiled versions of some static libraries or dynamic libraries in the project are inconsistent

Solutions:

In the final analysis, it’s an environmental issue: GCC, G + + version matching or the supplement of third-party dependency

Modify the cmakelist file as follows:

cmake_minimum_required(VERSION 3.17)
project(untitled)

set(CMAKE_CXX_STANDARD 14)
find_package( OpenCV REQUIRED )

include_directories(${OpenCV_INCLUDE_DIRS})
add_executable(untitled main.cpp)
target_link_libraries(untitled ${OpenCV_LIBS} )

#include <iostream>

using namespace std;

class Tmp1 {
public:
    int foo() { 
        cout << "Tmp1.foo" << endl;
        return ret;
    }

    string walk() {
        cout << "walk" << endl;
        return "cout walk";
    }

    int ret = 1;
};

class Tmp2 {
public:
    int foo() {
        cout << "Tmp2.foo" << endl;
        return ret;
    }

    string run() {
        cout << "run" << endl;
        return "cout run";
    }

    int ret = 2;
};

struct OutPara {
    int ret = 0;
    string desc;
};

template<typename T, typename F>
void print(T t, const F &f) {
    cout << "test" << endl;
    f(t);
}

int main()
{
    Tmp1 t1;
    OutPara out;
    print(t1, [&](Tmp1 &t)->void{
        out.desc = t.walk();
        out.ret = t.foo();
    });
    cout << out.ret << "\t" << out.desc << endl;
    Tmp2 t2;
    print(t2, [&](Tmp2 &t)->void{
        out.desc = t.run();
        out.ret = t.foo();
    });
    cout << out.ret << "\t" << out.desc << endl;
    return 0;
}

The output

test
walk
Tmp1.foo
1       cout walk
test
run
Tmp2.foo
2       cout run

Error:
Error LNK2019: Unable to resolve external symbol _main, which is referenced in the function ___TMainCrtStartup
Cause analysis,
I use VS2013 debugging an MFC program when the problem occurred.
1. You built a console program with VC. Its entry function should be main, and you used WinMain.

> You open a.c/.cpp file with vc and compile it directly, using Winmian instead of main as the entry function. VC’s default Settings at this point are for console applications.

Solutions:
1. Enter the project – & gt; setting-> C/C ++, select Preprocessor in Category, remove _CONSOLE in Processor Definitions, and add _WINDOWS
2. Enter the project – & gt; setting-> Link changes /subsystem:console to /subsystem: Windows in Projections.
3. Save Settings, Rebuild All.