Thanks, I was able to decipher that from the gcc documentation finally. Another question, if I want to optimize for core 2 duo, what -mtune should I use? Thanks, FM -----Original Message----- From: Ian Lance Taylor [mailto:iant@xxxxxxxxxx] Sent: Friday, February 08, 2008 6:48 PM To: Frank W. Miller Cc: gcc-help@xxxxxxxxxxx Subject: Re: 64-bit for OS kernel development "Frank W. Miller" <fwmiller@xxxxxxxxxxx> writes: > I am interested in using gcc to extend the development of an OS kernel > from 32-bit to 64-bit for Intel and AMD processors. > > If I use a compiler that is built for a 32-bit Linux distro, and I > change my types in the kernel code from 32 bit (long and unsigned long) > to 64 bit (long long and unsigned long long), will the resulting data > types use the native 64-bit types on the underlying machine? Only if you compile in 64-bit mode. A compiler for a 32-bit distro probably compiles in 32-bit mode by default. It may support the -m64 option to generate 64-bit code. Ian
