GCC compiler option for 64 bit

lilzz · 08-15-2006, 07:14 PM

original GCC makefile GCC flag
CCFLAGS=-Wall -m32 -march=i486 -Os -fomit-frame-pointer -fno-builtin -ffreestanding

modified for 64 bit
CCFLAGS=-Wall -m64 -march=i686 -Os -fomit-frame-pointer -fno-builtin -ffreestanding

error message
main.c:1: error: CPU you selected does not support x86-64 instruction set

how should I modify to make it compile for 64bit.
CPU I have is P4 2.2GHz

thanks

HappyTux · 08-15-2006, 07:16 PM

I no expert in this but should not it be -march=k8.

bulliver · 08-15-2006, 11:48 PM

Quote:

I no expert in this but should not it be -march=k8.

-march=pentium4 rather wouldn't you say?

Quote:

how should I modify to make it compile for 64bit.
CPU I have is P4 2.2GHz

You are aware that the P4 isn't 64 bit right?

If you are trying to compile code on your P4 for a different (actually 64bit) machine then I suggest you start with a google search for "gcc cross compiling"