Compiling 32-bit C/C++ Programs on 64-bit

By default, gcc will compile your c/c++ program to 64-bit instructions. In order to compile to 32-bit you need to add a -m32 flag to the command line. For example, to compile a file called hello-world.c using a Linux terminal, you would do something like this:

$ gcc -m32 hello-world.c -o hello-world

If you get the following error:

fatal error: bits/predefs.h: No such file or directory

it means that the multilib standard library is missing. Therefore, you must install gcc-multlib. The name is different based upon the distribution and the compiler. For Debian/Ubuntu-based distros it would be:

$ sudo apt-get install gcc-multilib # For C $ sudo apt-get install g++-multilib # For C++

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