Unsupported x86-64 instruction set error when compiling C file

Question

I am trying to follow the tutorials in this link.

When I get down to the part where I start making a test.c file, I try to run the first compilation line.

Answer 1

in fact add -m32 you can keep -march=i686 ...

gcc -c -g -Os -march=i686 -m32 -ffreestanding -Wall -Werror test.c -o test.o

works

gcc -c -g -Os -march=i686 -m16 -ffreestanding -Wall -Werror test.c -o test.o

works

gcc -c -g -Os -march=i686 -m64 -ffreestanding -Wall -Werror test.c -o test.o

fails with ;

test.c:1:0: error: CPU you selected does not support x86-64 instruction set asm(".code16\n");

Answer 2

gcc -std=c99 -c -g -Os -march=i686 -m32 -ffreestanding -Wall -Werror test.c -o test.o
ld -static -T test.ld -m elf_i386 -nostdlib --nmagic -o test.elf test.o

Answer 3

Supply -m32 instead of -march=i686.