x86 Assembly pushl/popl don't work with “Error: suffix or operands invalid”

Question

I\'m a newbie to assembly programming, working through Programming Ground Up on an Ubuntu x86_64 desktop with GNU assembler v2.20.1.

I\'ve been able to assemble/link

Answer 1

You may push any value without push command like that

decq %rsp
movb $0, (%rsp)

push 1 byte on stack and pop after

movb (%rsp), %al
incq %rsp

And any other size. As compilator don't generate any error and all will work good! To address may use rbp register instead of rsp. Now is allowed.