When should -m32 option of gcc be used?

Question

I am writing a program which if I compiler on Suse 10 32 bit system without adding the -m32 option and execute it on Suse 10 64 bit works fine.

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

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

Answer 1

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.

Answer 2

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..