Helo list, I'm using FC6 for x86_64. I need to compile a program for linux 32 bits. I tried with the -m32 flag to gcc, but I got: core_recv.c:(.text+0x130): undefined reference to `__umoddi3' and tons of ld warnings: /usr/bin/ld: warning: i386 architecture of input file `main.o' is incompatible with i386:x86-64 output I searched in Google, but couldn't find the solution. For the undefinded references I suppose it is because some missing i386 libraries right? And what about the other things? How can I compile a 32 bit application under a 64 bit system? Thanks in advance.