Help with CMake linking libraries | Together C & C++ | Page 1

soft basalt Jun 27, 2025, 4:52 AM

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Hey all, so I'm finding it really difficult to understand linking libraries-
can anyone help guide me through linking static and dynamic libraries using CMake and VSCode?

faint ginkgoBOT Jun 27, 2025, 4:52 AM

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soft basalt Jun 27, 2025, 5:00 AM

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I'm just a little frustrated, because not understanding this core concept of building and compiling C++ code is preventing me from diving head-first into learning C++ past the general syntax-

gentle spoke Jun 27, 2025, 5:24 AM

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What library do you wanna link?

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And show your cmakelists.txt and the errors you get, if any

soft basalt Jun 27, 2025, 5:38 AM

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okay so- I want to link glew and wxWidgets-
but I like dont understand how to link any libraries in CMake

gentle spoke Jun 27, 2025, 5:39 AM

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Okay. What OS and compiler?

soft basalt Jun 27, 2025, 5:40 AM

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I tested on OpenAL though- and successfully compiled it and ran it
But VSCode doesnt know where those files are-
Windows 10, Clang++ Visual Studio Code

gentle spoke Jun 27, 2025, 5:41 AM

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Oh cool, clang! Did you install it from msys2?

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Followed my tutorial by any chance?

soft basalt Jun 27, 2025, 5:41 AM

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yes ive been following it! :>

gentle spoke Jun 27, 2025, 5:42 AM

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I really need to write more about cmake 😛

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What you do is:

Install the library in msys2 if possible
In cmakelists.txt, do find_package(WhateverLibrary REQUIRED)
In cmakelists.txt, do target_link_libraries(YourTarget PUBLIC WhateverLibrary::WhateverLibrary)

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The exact spelling of WhateverLibrary and WhateverLibrary::WhateverLibrary is sometimes not obvious. I don't remember how to figure it out from scratch for a certain library, usually I just google

soft basalt Jun 27, 2025, 5:43 AM

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ohhh- and is that for dynamic libraries?

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or both?

gentle spoke Jun 27, 2025, 5:43 AM

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Works for both. I think it prefers shared (dynamic) libraries by default if both are available

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I don't use cmake too much, so I don't remember how to force it to use static

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But I'm not a big fan of static libs either

soft basalt Jun 27, 2025, 5:45 AM

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ah okay-
another question; I put my libraries in two folders in the project file, named /include/ and /lib/ respectively- and I plan to put all of the libraries in those
How would I point CMake to those?

gentle spoke Jun 27, 2025, 5:46 AM

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Mmm, so you want to manually download the libraries instead of installing them in msys2?

soft basalt Jun 27, 2025, 5:47 AM

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I would like to learn both ways yeah-
But is it better to just link through a msys2 install of the library?

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like is there gonna be a library that i cant download in msys2?

soft basalt Jun 27, 2025, 5:48 AM

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gentle spoke What you do is: 1. Install the library in msys2 if possible 2. In cmakelists.txt...

and what would the 'YourTarget' be? :0

gentle spoke Jun 27, 2025, 5:49 AM

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Definitely a lot easier to do it in msys2. But yeah, it's good to know how to install them elsewhere too

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So the "proper" way is to have a directory for the libraries that will contain include, lib, and some other directories. The directory that contains those is often called a "prefix".

To consume a library from a specific prefix, you do -DCMAKE_PREFIX_PATH=path/to/prefix. You can specify multiple paths too (the separator is either ; or :, could be OS-dependent, try both)

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So you can do one prefix per library if you prefer, or one fat one

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And if you use CMAKE_PREFIX_PATH like this, find_package will magically work

soft basalt Jun 27, 2025, 5:53 AM

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would cmake know where the .lib and .h files are just by pointing to the prefix folder?

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like, if they were contained in /lib/ and /include/

gentle spoke Jun 27, 2025, 5:53 AM

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In the prefix there would also be some .cmake files or whatever that tell it how to use specific libraries

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You don't create a prefix manually (by creating directories include, lib or whatever). Instead, when compiling the library, you specify -DCMAKE_INSTALL_PREFIX=path/to/prefix, and it'll create the prefix at that path and install (copy) the library to it

gentle spoke Jun 27, 2025, 5:54 AM

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soft basalt and what would the 'YourTarget' be? :0

And that would be the name you passed to your add_executable (or add_library if you're making a library)

soft basalt Jun 27, 2025, 5:54 AM

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ohhhh when you compile the library got it

gentle spoke Jun 27, 2025, 5:54 AM

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Yeah

soft basalt Jun 27, 2025, 5:55 AM

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gentle spoke And that would be the name you passed to your `add_executable` (or `add_library`...

oh okay!

gentle spoke Jun 27, 2025, 5:55 AM

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https://github.com/HolyBlackCat/cpp-tutorials/blob/master/tooling/articles/using_libraries_compiling_manually_cmake.md

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Here's how you compile libraries with cmake

soft basalt Jun 27, 2025, 5:59 AM

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gentle spoke What you do is: 1. Install the library in msys2 if possible 2. In cmakelists.txt...

okay so OpenAL is installed in msys2-
but it looks like its not able to find OpenAL

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OpenAL is installed though

gentle spoke Jun 27, 2025, 6:00 AM

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Cmake has to be installed in msys2

soft basalt Jun 27, 2025, 6:00 AM

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oh okay lmao

gentle spoke Jun 27, 2025, 6:01 AM

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Yeah. There's probably a way to use the one from the installer too, but msys2 cmake searches libraries installed in msys2 by default, which is nice

soft basalt Jun 27, 2025, 6:01 AM

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so, do i have to configure that differently in VSCode? or when I install it through msys2 it will just point to the msys2 directories?

gentle spoke Jun 27, 2025, 6:03 AM

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You just need to use msys2 cmake instead of your normal cmake. But I don't use the VSC cmake extension, so I'm not sure how to tell it to use a different cmake

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There's probably a setting somewhere

soft basalt Jun 27, 2025, 6:04 AM

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also- theres alot of cmakes when i do pacman -Ss cmake
How do I know which one to use? Should i go with mingw-w64-clang-x86_64-cmake or the one just called "cmake"
sorry for all the dumb questions- its all pretty confusing to me, im not used to having to manage libraries like this

gentle spoke Jun 27, 2025, 6:04 AM

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Yes, mingw-w64-clang-x86_64-cmake is the right one. In general, you wanna use mingw-w64-clang-x86_64-... when they are available

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MSYS2 has multiple copies of everything: compilers, libraries, build systems, etc. They are differentiated by those prefixes in the package names, such as this mingw-w64-clang-x86_64-, or no prefix at all in case of just cmake

(I'm using "prefix" in a different meaning here ofc 😛 )

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This stuff is explained here: https://stackoverflow.com/q/76552264/2752075

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I don't mind the questions at all

soft basalt Jun 27, 2025, 6:16 AM

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okay hmmm- its still not finding OpenAL

gentle spoke Jun 27, 2025, 6:18 AM

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Ah

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target_link_libraries goes after add_executable

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because add_executable is what creates the OpenAL_link_test target

soft basalt Jun 27, 2025, 6:18 AM

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oh! that worked!

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ahhh that makes sense yeah

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now when im adding multiple libraries- do i add a new line find_package([package_name] REQUIRED) for each new library?

gentle spoke Jun 27, 2025, 6:23 AM

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Yeah

soft basalt Jun 27, 2025, 6:24 AM

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then for the target_link_libraries how would I separate that out? or would I need to do multiple target_link_libraries calls

gentle spoke Jun 27, 2025, 6:25 AM

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target_link_libraries(blah PUBLIC A::A B::B C::C)

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You can separate it into multiple calls, I don't think there's a difference

soft basalt Jun 27, 2025, 6:25 AM

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ah okay! but i cant dot the same for find_package, it has to be separate?

gentle spoke Jun 27, 2025, 6:25 AM

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I think so

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Because it can take a bunch of other arguments (the specific library version, etc)

soft basalt Jun 27, 2025, 6:27 AM

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ah got it okay! thanks so much for your help i really appreciate it!
first major hurdle tackled!

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!solved

#Help with CMake linking libraries