简单的 CMAKE 教程有问题

如何解决简单的 CMAKE 教程有问题

我只是按照 youtube 上的简单 CMake 教程进行操作 https://www.youtube.com/watch?v=V1YP7eJHDJE

正如你在 YouTube 上看到的， 文件夹目录是

CMAKE-GOOD
-build
-CMakeLists.txt
-main.cpp

这是 CMakeLists.txt

cmake_minimum_required(VERSION 3.14)

project(MyProject VERSION 1.0.0)

add_executable(cmake-good main.cpp)

这是 main.cpp

#include <iostream>
int main()
{
    std::cout << "hello,world! \n";
}

这是我编写的唯一源代码。 从这部分开始，这将涵盖我遇到的错误

edit) 我也在构建目录中做了 cmake .. 结果如下图

(base) bmssa@bmssa:~/Desktop/CMake_tutorial/CMAKE-GOOD/build$ cmake ..
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/bmssa/Desktop/CMake_tutorial/CMAKE-GOOD/build

当我在 cmake --build . 中输入 ~Desktop/CMake_tutorial_CMAKE_GOOD/build 时，它显示一个错误

(base) bmssa@bmssa:~/Desktop/CMake_tutorial/CMAKE-GOOD/build$ cmake --build .
[ 50%] Linking CXX executable cmake-good
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
CMakeFiles/cmake-good.dir/build.make:96: recipe for target 'cmake-good' Failed
make[2]: *** [cmake-good] Error 1
CMakeFiles/Makefile2:82: recipe for target 'CMakeFiles/cmake-good.dir/all' Failed
make[1]: *** [CMakeFiles/cmake-good.dir/all] Error 2
Makefile:90: recipe for target 'all' Failed
make: *** [all] Error 2

我听说 cmake --build 。类似于 make， 所以我尝试了 make 并且它显示了这样的错误

(base) bmssa@bmssa:~/Desktop/CMake_tutorial/CMAKE-GOOD/build$ make
[ 50%] Linking CXX executable cmake-good
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
CMakeFiles/cmake-good.dir/build.make:96: recipe for target 'cmake-good' Failed
make[2]: *** [cmake-good] Error 1
CMakeFiles/Makefile2:82: recipe for target 'CMakeFiles/cmake-good.dir/all' Failed
make[1]: *** [CMakeFiles/cmake-good.dir/all] Error 2
Makefile:90: recipe for target 'all' Failed
make: *** [all] Error 2

当我输入 cmake --version 时，

cmake version 3.20.0

CMake suite maintained and supported by Kitware (kitware.com/cmake).

你能帮我解决这个问题吗？ 我什么也做不了，因为我什至无法在非常简单的教程中解决这个简单的错误。 请帮助我 谢谢

ps。 因为我什至不知道 CMake 中的错误是什么，你能告诉我我应该在 google 中输入什么来解决这个问题吗？

目标食谱？ 目标“全部”的配方失败？

我不知道我应该在 google 中输入什么....

edit2) 我也做了 cmake -S . -B build/foobar 和 cmake --build build/foobar 这也显示了类似的错误

(base) bmssa@bmssa:~/Desktop/CMake_tutorial/CMAKE-GOOD$ cmake -S . -B build/foobar
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/bmssa/Desktop/CMake_tutorial/CMAKE-GOOD/build/foobar
(base) bmssa@bmssa:~/Desktop/CMake_tutorial/CMAKE-GOOD$ cmake --build build/foobar
[ 50%] Building CXX object CMakeFiles/cmake-good.dir/main.cpp.o
[100%] Linking CXX executable cmake-good
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
CMakeFiles/cmake-good.dir/build.make:96: recipe for target 'cmake-good' Failed
make[2]: *** [cmake-good] Error 1
CMakeFiles/Makefile2:82: recipe for target 'CMakeFiles/cmake-good.dir/all' Failed
make[1]: *** [CMakeFiles/cmake-good.dir/all] Error 2
Makefile:90: recipe for target 'all' Failed
make: *** [all] Error 2

解决方法

这是我对您的问题的猜测。 CMake 无法找到工作工具链（编译器、链接器等）

尝试通过指定环境变量 CC 和 CXX 来帮助它。

• https://cmake.org/cmake/help/latest/envvar/CXX.html
• https://cmake.org/cmake/help/latest/envvar/CC.html

export CC = /foobar/...../gcc
export CXX = /foobar/...../g++

这里是 CMake 查找编译器的方法（根据 CMake 开发人员的说法），供将来参考

1. CMAKE_TOOLCHAIN_FILE（如果提供）
2. CMAKE_LANG_COMPILER（如果提供）
3. 环境变量 CC 或 CXX（如果提供）
4. 然后它搜索路径环境变量以查看是否可以找到任何内容。

我想在你的情况下，以上都没有奏效。所以设置 CC 和 CXX 就解决了。