When should -m32 option of gcc be used?

I am writing a program which if I compile on a Suse 10 32-bit system without adding the -m32 option and execute it on Suse 10 64-bit, it works fin开发者_JS百科e.

In this case, is it not required for me to add the -m32 option?

Can we execute programs built on 32-bit systems directly on their 64-bit counterparts without any side-effects? Or are there any updates or changes required?

There is no problems in running 32 bits executables on 64 bit OS (as long as 32 bit dynamic libraries are present and found).

-m32 is there to compile 32 bits objects on a compiler configured to compile 64 bits objects by default.

As long as the OS supports both 32bit and 64bit programs (hint: not all do, such as OpenBSD) on a 64bit OS, then you shouldn't have any kind of problems as long as you have all of the 32bit dependencies for it..