ysflight.com - Cross-Compiling 32-bit OpenGL program in 64-bit Ubuntu |
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2014/07/11 I'm writing this document on July 11, 2014. But, I could not cross-compile 32-bit OpenGL program in 64-bit Ubuntu (until I found this work around, of course) only because of a known bug. I hope someone fixes it and un-necessitate this document soon. I saw some questions from someone who were trying to do the same, but I didn't find an answer nowhere. Probably they are still looking for an answer. I hope this work around helps them. Until now, I was compiling 32-bit binary on 32-bit Ubuntu, and 64-bit binary on 64-bit Ubuntu. I launch a different virtual machine in VirtualBox for each case. But, it's not very efficient. It is the same operating system. I have been wanting to build and package both 32-bit and 64-bit version binary from one script. There are options -m32 and -m64 of gcc, which force the compiler to spit out 32-bit and 64-bit binary respectively. However, if I tried gcc -m32 in 64-bit Ubuntu, I was getting an error complaining predef.h not found. Today, somehow that problem came back to my mind. I searched for the solution and learned that what I needed was multilib libraries. Further search indicated that not all libraries are as convenient as multilib, but I can do sudo apt-get install lib???:i386 to get 32-bit version libraries in most cases. That made me hopeful. I thought it should be easy to set up cross-compiling so that I can compile both 32-bit and 64-bit binaries in 64-bit Ubuntu. Then I hit a brick wall. After installing multilib, gcc told me that libGL and libGLU cannot be found. Not a big deal. I should be able to apt-get install libgl1-mesa-dev:i386 and libglu1-mesa-dev:i386 to install 32-bit version of libGL and libGLU, right? Unfortunately it turned out not so easy. apt-get gave me an error and could not install 32-bit libGL and libGLU. Search implied that it is one of the known bugs of Ubuntu (or Debian). https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/1317113 If Microsoft leaves known bugs unfixed long time, it's a shame. Like Microsoft Office Drawing Tools have been broken for long time. But, Linux is an open source software. All I can do is shrug and give up, usually. But, this time I didn't give up. What gcc is complaining was missing 32-bit libGL and libGLU. I have them in my 32-bit Ubuntu. I can copy them from there. About half-day struggle, this strategy worked. I finally was able to build 32-bit OpenGL program in 64-bit Ubuntu and run. My impression is that some people are having the same problem. I summarize what I did below. Hope this information helps some fellow OpenGL programmers.
Step 1. Installing Mesa libraries in 32-bit Ubuntu I am assuming you are running Ubuntu in VirtualBox. You should be able to do the same from a natively-running Ubuntu. You probably need to have 32-bit Ubuntu of the same version as your 64-bit Ubuntu. I am using Ubuntu 12.04. The goal is to copy OpenGL libraries, you need to install libgl1-mesa-dev and libglu1-mesa-dev, at least. Then, create a shared folder of VirtualBox. You will copy library files to the shared folder, which later will be copied into 64-bit Ubuntu. Step 2. Copy Mesa libraries to the shared folder in 32-bit Ubuntu Type the following: % locate libGL to find where Mesa libraries are located. It shows you libraries that starts with libGL. So, you will also see GLU libraries. In my environment, I had to copy: /usr/lib/i386-linux-gnu/libGL* to the shared folder. I also had to copy ALSA and Pulse Audio libraries, which also were not cross-compiling friendly. I could use the same technique for these libraries. Of course if you only need OpenGL, you don't need ALSA and Pulse Audio. You don't need 32-bit Ubuntu at this point. You may want to keep it only for testing your 32-bit binary. Step 3. Installing multilib in 64-bit Ubuntu Type following in 64-bit Ubuntu to install multilib packages. % sudo apt-get install gcc-multilib This creates a directory for 32-bit libraries. In my environment, it was /lib32. But, some people are saying it is /usr/lib32. You can find by yourself. Step 4. Copying 32-bit library files to the 32-bit library directory. If you haven't mounted the shared folder where 32-bit library files are copied, please do so now. If you are running native Ubuntu, both 32-bit and 64-bit, maybe you can do it via a USB drive. What's important is to copy 32-bit library to the appropriate directory. In my environment, I had to type: % sudo cp /ysshare/libGL* /lib32 /ysshare was my shared directory. You may want to keep copied libraries in a separate location and make a symbolic link so that you can clean up the copied libraries easier if necessary later time. Step 5. Installing other 32-bit libraries You also need the following packages to cross-compile an OpenGL program. % sudo apt-get install libX11-6:i386 Then, all you need to do is compiling with -m32 option. I tested with PolygonCrest and YSFLIGHT. I could build 32-bit binaries of the both programs in 64-bit Ubuntu, which ran ok in both 32-bit and 64-bit Ubuntu. If you mixed up something, you may see an error message whey you try to run your 32-bit OpenGL program in 64-bit Ubuntu like lib???.so.1 not found. Then, you may have to do: % sudo ldconfig Probably that will fix. So, now I am able to compile both 64-bit and 32-bit binaries of PolygonCrest from one script. I need to do the same for MacOSX, then I can upload the program.
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