安装CMake之后，我找不到带有`find_package`的软件包

Question

I have installed a library (SDL) with the following command:

cmake --build . --target install

I read in the documentation that installed packages are going to be registered in the CMAKE_SYSTEM_PREFIX_PATH .

But when I print out the variable it is empty.

Currently I am using Windows, and I read online that I should register the installation path in the registry, but it did not help at all.

How can I find, for example, SDL with find_package()?

Answer 1

Try this:

Using the get_cmake_property function the following loop will print out all CMake variables defined and their values:

 get_cmake_property(_variableNames VARIABLES) list (SORT _variableNames) foreach (_variableName ${_variableNames}) message(STATUS "${_variableName}=${${_variableName}}") endforeach() 

To print environment variables use CMake's command mode:

 execute_process(COMMAND "${CMAKE_COMMAND}" "-E" "environment") 

It prints:

-- CMAKE_SYSTEM_PREFIX_PATH=/usr/local;/usr;/;/usr;/usr/local;/usr/X11R6;/usr/pkg;/opt

(Credits to Sakra )

You can search your source tree for a file named FindSDL*.cmake then try to find this file in your CMAKE_SYSTEM_PREFIX_PATH directories.

If CMAKE_SYSTEM_PREFIX_PATH is still empty, try to locate FindSDL*.cmake in your entire computer to check whether files are being installed somewhere cmake knows or try to append this path to your CMAKE_SYSTEM_PREFIX_PATH .

You can also check this link: Using SDL2 with CMake

Answer 2

I believe the reason this wasn't working for you is because your find_package command came before your project command in your CMakeLists.txt file. If you ensure project is the first command (after cmake_minimum_required(VERSION <NUM> ) then all of the CMAKE_SYSTEM_*** variables will be initialized correctly :)

I actually stumbled across this post after having the exact same problem (see my comment on the initial question). I tried the advice posted by j4x using the foreach VARIABLES command to print all the variables and serendipitously pasted it after my project command. I noticed CMAKE_SYSTEM_PREFIX_PATH was a sensible value - I then moved the code above the project command and noticed far fewer variables were printed :P CMAKE_SYSTEM_PREFIX_PATH was no where to be seen...

I hope this works for you too!