I have two different libGL libraries on the same Ubuntu 11.04 machine. One library was installed for the Nvidia's graphics card at /usr/lib/libGL.so the other is the default that came installed with Ubuntu, located at usr/lib/x86_64-linux-gnu/mesa/libGL.so.
Now, the problem I have is the Qt library downloaded from Ubuntu's repositories links against the mesa library, but I want to link against Nvidia's library. This will probably give better performance, and there have been issues using mesa's libGL when compiling a program. Those have been fixed by:
export LIBGL_ALWAYS_INDIRECT=1
To my knowledge this forces X11 to choose the openGL library, and it is choosing the correct one. But, I would much rather have Qt and the program that is compiled with QtOpenGL be linking directly with the correct library.
I downloaded Qt and compiled it myself using these options:
./configure -nomake examples -nomake demos -nomake tools -release -no-webkit
I hoped the linker would use the correct library. No dice. Next, I tried editing the mkspec/linux-g++-64/qmake.conf with these variables set:
QMAKE_LIBDIR_X11 = /usr/lib/x86_64-linux-gnu
QMAKE_LIBDIR_OPENGL = /usr/lib
Is there an option where I can force the linking of a specific library instead of another (specifically when the configure script is run)? I would prefer not to configure the linker in any specific way. I would also rather not remove the mesa library.
If there is no such configure script flag to do so, is there a way to set precedence of libraries the linker uses?
Worst case scenario, I could probably change all the Makefiles after ./configure is run. Grep the entire Qt tree for use of -lGL and change it to /usr/lib/libGL.so. I feel this is quite a hack though.
Update
Some success. I did a grep on the Qt tree for lGL and found that other mkspecs (besides linux-g++-64) used other variables to specify OpenGL path. So I added them to linux-g++-64's mkspec, here's the result of mkspec/linux-g++-64/qmake.conf:
QMAKE_LIBS_OPENGL = /usr/lib/libGL.so
QMAKE_LIBS_OPENGL_QT = /usr/lib/libGL.so
So I set the path to the library I wanted directly thinking it would link properly. Indeed it was good news, during the compilation, -lGL was never used. However, the ultimate result was lib/libQtOpenGL.so is still linked with the wrong library:
$ ldd lib/libQtOpenGL.so
linux-vdso.so.1 => (0x00007fffd83ff000)
libQtGui.so.4 => (edited)lib/libQtGui.so.4 (0x00007f554c684000)
libQtCore.so.4 => (edited)lib/libQtCore.so.4 (0x00007f554c19c000)
libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f554beda000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f554bcd6000)
**libGL.so.1 => /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1 (0x00007f554ba7a000)**
libXrender.so.1 => /usr/lib/x86_64-linux-gnu/libXrender.so.1 (0x00007f554b86e000)
libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007f554b536000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f554b22f000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f554afaa000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f554ad94000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f554a9f5000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f554a7d7000)
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f554a4e1000)
libpng12.so.0 => /lib/x86_64-linux-gnu/libpng12.so.0 (0x00007f554a2ba000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f554a0a1000)
libSM.so.6 => /usr/lib/x86_64-linux-gnu/libSM.so.6 (0x00007f5549e99000)
libICE.so.6 => /usr/lib/x86_64-linux-gnu/libICE.so.6 (0x00007f5549c7f000)
libfontconfig.so.1 => /usr/lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f5549a48000)
libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007f5549835000)
libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f554962f000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f5549427000)
/lib64/ld-linux-x86-64.so.2 (0x00007f554d66f000)
libglapi.so.0 => /usr/lib/x86_64-linux-gnu/libglapi.so.0 (0x00007f5549203000)
libXdamage.so.1 => /usr/lib/x86_64-linux-gnu/libXdamage.so.1 (0x00007f5548fff000)
libXfixes.so.3 => /usr/lib/x86_64-linux-gnu/libXfixes.so.3 (0x00007f5548df9000)
libXxf86vm.so.1 => /usr/lib/x86_64-linux-gnu/libXxf86vm.so.1 (0x00007f5548bf3000)
libdrm.so.2 => /usr/lib/x86_64-linux-gnu/libdrm.so.2 (0x00007f55489e7000)
libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f55487cb000)
libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f554858e000)
libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007f5548389000)
libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f554815f000)
libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007f5547f5b000)
libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f5547d55000)
I have no idea why, I specified directly what library to use and it was passed correctly to g++, but the linker apparently ignored it. I believe it is no longer a Qt problem, but a linker problem.
Is there any way with ldconfig or other tools to specify what library to link to in case of -lGL? I know other libraries have a program which will organize what library to use (libusb-config comes to mine), but I do not think this is the case with openGL.