CMake Tutorial EP 3 | Git Submodules (adding glfw windowing library example)
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- เผยแพร่เมื่อ 6 ก.ย. 2024
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The -D predates CMake and is part of gcc syntax for a definition which gets translated to a #define statement. Other executables (like java) use this convention as well for injecting variables (of one kind or another) in from the command line.
16:00 in target_link_libraries you reference other targets, in this case glfw specifies a target. This comes from the call to add_library() in external/glfw/src/CMakeLists.txt. In that CMakeLists.txt file you can see that they somehow set the name of the target library to glfw3 (for whatever reason), but the beauty of using targets is that you don't need to care about how it is actually called. You work only with the target name which can be completely different than the library name.
Damm 3 weeks old answer on 2 years old video. looks I really watch it at the right time. Please pin the above comment Code, Tech, and Tutorials.
@@priyanshu_hiro I would recommend reading the docs to whatever CMake functions are used in the video. Then you would know that it isn't the isn't the lib name, its the target name.
Apparently they set the "OUTPUT_NAME" property (used by CMake to determine the actual filename) on the "glfw" target to "GLFW_LIB_NAME", which in turn is set to "glfw" or "glfw3" based on a condition.
I was trying to build GLFW into my project from a git submodule for 9 hours, learned compiling, learned linking, learned cmake, with the first and second tutorial... I spent 3 hours searching about how things were seen by various linkers and whatnot...
then I noticed there was a 3rd tutorial episode.
don't know if i suck at finding it but this was the only good tutorial on git submodules, thanks a lot
same here!
I think we use glfw instead of glfw3, because we should put here the parameter, which was used in add_library(glfw [...]) (in external/glfw/src/CMakeLists.txt,). The same was for Adder. Let me know if it's a good way of thinking about it :)
Yes you are right .
Yes, that can be done but he is trying to keep things as simple as possible because many viewers are basically at beginner level in CMake. Eventually, he covers how to add ANYTHING and several ways of doing it.
Then why is the built library named "libglfw3.a" and not "libglfw.a"?
@@anddero it is because external/glfw/src/CMakeLists.txt set so in the very first line add_library(...).
Thanks so much for these videos man! I know you're more of a small TH-camr, but I don't like the other videos on TH-cam about CMake as much as yours. Your examples, even though sometimes you make a lot of errors along the way, actually help me learn a lot better, because I see what doesn't work and what does Usually it makes me learn _why._ This is very helpful for me, because I can get a sense of what under-girds the principles behind these tools. Thanks so much man!
Very well done and very helpful for the total NOOB. I enjoy the little bit of light humor. Keeps things from getting too bland.
Do not try to add multiple directories via one add_subdirectory() command (it is not even plural!!!) as i tried to. It works, but only the first directory is added which results in linking errors!!!
EXTREMELY helpful tutorial series! I've been trying to get this setup since 2014, unsuccessfully. I know I'm dumb but it's generous digital elves like you that save grace upon this wretched planet 😅
I enjoy the small jokes you slip in, "git into git" and the binocular vision when something in the Cmake documentation piqued your interest in the last episode. Informative and funny, thanks for this series.
Literally trying to figure out how to setup a cross platform project for Linux/Windows that uses GLFW and CMake and just found this series, thankyou, such relief to have someone explain this in simple terms.
Thank you for the wonderful explanation of the teeny tiny details! Great to learn as a beginner!
I feel like a will become the very Lord and Savior by end of this course! Great job!
10:21 "-D" is use for option because it's actually #define of particular macro.
this play list is my main reference whenever I want to use CMake, extremally helpful
Thank you for this tutorial, as a novice in CMake, it really helped me in my project.
It probably has been mentioned below. But the target_link_directories don't seem to be needed since you actually use the names in the add_library commands and not the names of the library files. That's why you use glwf and not glwf3 since the CMakeLists.txt of GLWF uses the add_library(glfw ...) command to create the library
Well, at least as a noob, that's how see to understand it
Exactly!
Regarding cmake targets (around the 14:30 mark): target_include_directories refers to the directories that the target needs to search for its own include headers (in this case adder). If that target were to be used as a dependency of a different target (like glfw here), its directories would be transitive and be passed on (provided they are public) by just adding the cmake target in target_link_libraries.
Having said that, adding another target’s directories to the target in question is kind of hijacking it to make the directories visible at compilation time. Hope this wasn’t too confusing.
i think in this example target_include_directories is not necessary as these header file directories from library are already included when building the libraries, and when you do the target_link_libraries it will add its interface_include_directories to the current target include_directories automatically.
Nice tutorial! Really appreciate it!
This tutorial is amazing! Best one I came across :)
Make this is top notch tutorial! This is such a complex topic and you make it look so easy.
Thank you thank you, this was the video that finally helped me get SFML configured for VSCode and CMake on a Mac.
Glad it helped!
glfw3 is a library name but cmake needs a target, which is glfw.
This series is so great! Really push me to tick CMake off my to-learn list!!!
this tutorial is pure gold
Thanks for the great tutorial man, very well made and easy to understand.
Glad it helped!
re: 10:22 why "D" is option. The -D* is probably mimicking the way that g++ does macro [D]efinitions
Oh Zeus you're the real saviour, thy shal be thanked!
thanks for the awesome tutorial and didn't know he bring his twin brother to talk this time lol.
Thanks a lot for the video. Best explanation overrall.
A change needed in CMakeLists.txt (line 29): "external_modules/glfw" --> "external/glfw".
but he did change it during the video right ?
These courses are fantastic.
You're the man!!! So easy to follow you.
Thanks! glad you found it helpful
OMG Somebody stole your goatee, did you have it insured ? Haha 😄 another great tutorial!!
Awesome series. Been a great help for my project👏
What if my submodule only has MakeFile not CMakeLists?
This was very helpful. Thank you!!
I wonder what would happen if I import two submodules with options having conflicting names, and I want to have one of them ON and other OFF.
Thanks for the video.
Thanks, Sir! I learn a LOT!
Question: why is the libglfw3.a file generated in the src dir (though it involves under 'build' dir)? Is it source code?
And when we include the path of libglfw3.a, why don't we need to include the 'out/build' in front of it?
Because he links to the CMake library (created by using add_library() inside glfw sources) which knows the path and the final name (.i.e. the 3 at the end of the name). Also, if glfw is created as STATIC or SHARED, from outside you dont need to care about .a or .so (that's a real added value about how CMake simplifies things)
thank you
where I can find the source code? It's no longer in the description.
I have subbed. Your channel is awesome. Thank you so much 🙏
Thanks for the sub!
This is a great series! Thank you!
Thank you!
Good tutorial. Thank you!
This is very so good lecture!!!!! Great job!!!! Thanks!
You're very welcome!
Amazing tutorials!
fascinating explanation, best regards
Thank you very much!
thankyou for your efforts bro...!
Hi, thanks for the tut, I wonder what does this "#!" mean, and when I use it on my windows, the command just won't work, tells me '#!' is not recognized as an internal or external command....
It's a Linux bash thing. On Windows unless you're using WSL and a Linux console, you might have to do something different
Cool video and explanation
Maybe someone can help and explain why do we need "target_link_directories"? And what is the difference with target_link_libraries?
I wrote the code without "target_link_directories", but with "target_link_libraries" and it still works just fine.
target_link_directories will tell CMake what directory/folder to look for libraries for the given target. Different OS's will have their default library search paths, but target_link_directories will allow you to specify where to search before the default library search paths.
target_link_libraries actually links the library files to the target so that the function definitions of the library can be used in the target.
I think that this call to target_link_directories is unnecessary because of the call to add_subdirectory for glfw3
Really good tutorial!!!
Thank you!
My god. Thanks a ton. Sincerely.
When building I got the following error: /home/pavel/Projects/olas/external/glfw/include/GLFW/glfw3.h:241:12: fatal error: GL/gl.h: No such file or directory
#include . I fixed it by modification of glfw3.h, which is not the correct way I guess. Any advice, please?
Yes same issue, thanks for mentioning it
Okay so i just needed to install the libglu1-mesa-dev packages
sudo apt-get update -y
sudo apt-get install -y libglu1-mesa-dev
thanks bro it WORKED!!! I was wandering aimlessly for 2-3 hours @@maximilien7737
Thanks for the very helpful tutorial! What about libs like GLEW ? That don't have CMakeLists.txt in treir repos ? How can you add them as a submodule ? or is there a different approach for those ? Thx and keep up and the good work!
You can, it can get a little complicated though and will vary from case to case. In my video on bgfx I use submodules and cmake to include bgfx and bgfx doesn't use cmake so that is one example. I'll try to cover more of this in upcoming cmake tutorials.
Great tutorial. Made me subscribe to your channel. :)
Awesome, thank you!
If I remove the `target_include_directories(...)` it can still be run without problem. Any idea?
btw, I think -D means Define variable
IN the cmake docs it says that `target_include_directories(...)` is rarely necessary, if you already use `link_library()`, you don't need it.
TY SO MUCH!!!
Firstly , Thank you for great tutorial !
I have a question. I add git submodules glad and sdl2. when glad build , it build a glad.c and glad.h so i can't target_include it in cmake . How can i make it work ?
Thanks! I recall having trouble submoduling both of those as well, it has been a while since I've tried again. If I ever figure it out I'll be sure to make a video.
@@CodeTechandTutorials Thanks u ! I look forward to it.
Thanks
Welcome
good tutorial!
I have a question. In main.cpp you include . Why did you include as a system library? #include "glfw3.h" seems more reasonable to me due to target_include_directories(${PROJECT_NAME}
PUBLIC Adder
PUBLIC external/glfw/include
)
However, that solution throws me an error during compilation. What am I missing?
Nice video anyway! It helps me to understand cmake much better!
The angle bracket includes doesn't necessary mean it is a system lib, it just means its within the projects known include directories. target_include_directories puts -I/path/to/include on the compile command for the objects so is sufficient. Quotes should work just the same really, it just searches the local directories first before checking the known includes. Hope that makes sense.
In this example, I noticed there's nothing in the folder:
external/glfw/include
The only thing there is another folder, GLFW, which means when I did THIS in the CMakeLists.txt file:
target_include_directories(${PROJECT_NAME}
PUBLIC external/glfw/include/GLFW
)
it worked to do #include or #include "glfw3.h".
EDIT: DON'T DO THIS, you should include the folder explicitly named "include" if there is one, to follow best-practices/C++ conventions.
So in this case, you'd write: #include or #include "GLFW/glfw3.h".
Sorry for the confusion!
@@carlosdalomba This is not correct however. You must set include dir as external/glfw/include and do #include "GLFW/glfw3.h" not just #include "glfw3.h". This is a convection, but you must follow it, because the library itself (or any other library) will follow it internally - the library will do MYNAME/myinclude, assuming the folder that contains MYNAME is added to include directories. Again this is universal assumption - if the public headers are in a folder with the same name as the library, you set the containing folder as include directory.
@@YourCRTube Ohhh I see, so it's (almost) universally assumed as a convention to include the "include" folder (if there is one)?
Thanks, that makes sense then, I'll edit my comment lol >.> oops
@@CodeTechandTutorials Hopefully, a simple question with a simple
answer. The window which appears is the old style. It says "Gears" and
the only button is a exit (X) one and it is NOT a radio button but the
generic one. The window is black but the header bar on top of the window is white instead of the gray one in the tutorial. I watched the video a couple
more times and looked at my code but could not find the problem. Any thoughts?
Your videos are great; make me sub to it. I have followed this video, didn't get any error, but the window didn't pop up :( What did I miss?
10:25 my guess D was used because D could mean "Dependency" but I dont think it means Dependency, but perhaps thats why they chose D because the options that people use could be seen as build deps.
git into git............... I'm dead
what happened to ur hair? on previous video u were more like Jesus, i liked it better)
It got scissored... and its long again!