CODEWITHSUNDEEP
c++linuxopengllinker-errorsqt5
David Burson
David Burson

Reputation: 3197

/usr/bin/ld: cannot find lGL when building Qt5 app in Qt Creator on Linux Mint

I'm porting my application from Qt4 to Qt5. I installed Qt5.2.1 from the online installer on Linux Mint 16 64-bit, in a vm on my MacBook Pro. When I run qmake and build in Qt Creator, I get:

/usr/bin/ld: cannot find -lGL

Do I need openGL? I'm not using it when I build on Windows or OSX. I'm very new to Linux, and far from expert in C++ or Qt. I found a post that included a hack to remove -lGL from mkspecs/common/linux.conf. That worked.

My question is, assuming I don't need -lGL, what is the normal way to keep the linker from attempting to link it? I imagine I do something in the .pro file, but what?

Upvotes: 1

Views: 2500

Answers (1)

datenwolf
datenwolf

Reputation: 162164

Qt5 makes heavy use of OpenGL internally. On Windows OpenGL support is a bit flaky (you must install the original vendor drivers, because Microsoft strips OpenGL from the automatically installed drivers) and hence makes use of a built in OpenGL emulation layer library.

On Linux however OpenGL support is much better. You'll find at least the Mesa softpipe backend, if the GPU is not supported by the standard drivers. If the GPU is supported, then out-of-the-box OpenGL support in Linux has become pretty good over the past years.

On MacOS X OpenGL is actually the foundation of all the higher level graphics operations and hence part of the inner workings of the operating system; sounds great in theory, but is also a major obstacle for quick version turnaround, as every major OpenGL version bump mandates an operating system update.

Now, unless your installation of Linux is seriously outdated you actually should have a OpenGL library installed. If not (and your linker error tells you this), just install the Mesa development package.

Linux Mint is a derivative of Ubuntu which in turn is a Debian derivative. The command to install the Mesa development package for OpenGL is

sudo apt-get install libgl1-mesa-dev

Upvotes: 1

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