C++: Using 3rd party libraries in QT Creator
My first web request
While in the very early stages of building Dorin Browser, I got to the point when I had to implement a web request functionality that would let it fetch resources from the internet.
Being a total newbie when it comes to C++, I had no idea how to do this. I was still half way through my “The C++ Programming Language” book by Bjarne Stroustrup, and there was no mention yet on how to do this.
Being eager to get this pretty important feature added to the browser, I dockduckgo’d “how to make a web request in cpp” and the first StackOverflow result that popped up, had as answer the curlpp library.
This sounded good to me. It’s a wrapper around the trusted libcurl library and the API seemed quite friendly.
3rd party libraries in C++
I felt like I was on the right path, now that I knew what library I’m going to use, but I had no idea how to actually get it into my project.
Most of the languages that I used to work with before, like JS, Java, Go, had some kind of a de facto package manager that would let you, relatively easy, add 3rd party packages to your project.
It seemed that even though there are some kind of package managers for C++, many developers prefer not to use one, and I was quite happy not to use one either. Having all my dependencies next to my source code, without needing to download stuff off the internet, was a very appealing idea and I still love it.
So, I had to figure this one out. My very brief research showed that there are two main ways of including libraries into a C++ project. That is, statiacally linking them or dynamically linking.
Static linking will take the source code of your library and build it into your program at compile time.
Dynamic linking will compile the library in a separate file which your program is going to use it.
So I decided to go ahead with having curlpp as a statically linked library.
My dev environment
I’m running on Linux Mint 19.1 and my IDE is QT Creator 4.12.3 based on Qt 5.14.2
If you’re on a different platform or using a different IDE, you’ll probably have to do things slightly different.
Adding the library to the project
The first thing you want to do, is make sure you have libcurl installed on your machine.
sudo apt-get install libcurl4 libcurl4-openssl-dev -y
This is required because curlpp is basically a wrapper around libcurl.
Getting the source code
Next, we have to download the actual source code from https://github.com/jpbarrette/curlpp/releases/tag/v0.8.1 (pick the latest version) and copy it into your project folder. Depending on how you have structured your project, you might want to have it inside a /libs folder.
Now you should have the curlpp source code within /your-project/libs/curlpp-x.x.x
Compiling the library
Inside the curlpp folder that you have just copied (curlpp-x.x.x), we are going to create a build folder, where the library is going to be compiled.
mkdir build cd build cmake .. make
Compiling the library is a necessary step for either statically or dinamically linking to it. That is unless you just download the binaries.
Adding the library to the project
Right click on your project and click on Add Library…
Select External libarary
Choose the newly built library file libcurlpp.a. This is telling the IDE that you want to use a statically linked library. Also select the Include path, which is a folder inside the curlpp-x.x.x folder.
QT Creator is going to auto-generate new config and place it in your project’s *.pro file. It is going to look something like this:
And that was it. Nothing complicated once you know how to do it :) Dorin Browser can now make web requests and get the beautiful source code which I yet have to parse and render.