下面是著名的hello world！程序，此文将逐行解释c程序使用gcc 编译生成的汇编的 汇编程序。
hello.c
#include <stdio.h>
int main(void){
printf("hello.\n");
return 0;
}
编译生成汇编文件hello.s
gcc -S hello.c
.file "hello.c"
.section .rodata
.LC0:
.string "hello."
.text
.globl main
.type main, @function
main:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
leaq .LC0(%rip), %rdi
call puts@PLT
movl $0, %eax
popq %rbp
.cfi_def_cfa 7, 8
ret
.cfi_endproc
.LFE0:
.size main, .-main
.ident "GCC: (Ubuntu 7.2.0-8ubuntu3) 7.2.0"
.section .note.GNU-stack,"",@progbits
解释 line by line
.file "hello.c"
# 汇编来源的原始文件名
.section .rodata
# 定义一个data section，里面的数据是ro（read only的）
.LC0:
# .LC0 local constant, e.g string literal.
.string "hello"
.text
# 代码开始
.globl main
# global makes the symbol visible to ld.
# 定义一个全局可见的symbol
# We define a function called "main" and
# globally visible (other object files will be able to invoke it).
.type main, @function
# set the type of a symbol.
# 定义symbol main 的类型为一个function
.LFB0:
# .LFB0 local function beginning
pushq %rbp
movq %rsp, %rbp
leaq .LC0(%rip), %rdi
call puts@PLT
movl $0, %eax
popq %rbp
ret
# funtion exit
.LFE0:
# .LFE0 local function ending,
.size main, .-main
# set the size associated with a symbol
# 设置symbol main 的大小
# “.-main” ： 从当前位置到main
.ident "GCC: (Ubuntu 7.2.0-8ubuntu3) 7.2.0"
# 备注编译器版本
.section .note.GNU-stack,"",@progbits
# 意思是这个segment会被标记为 “非可执行栈”（栈中不能存可执行的指令，只存数据）
# With this section, the executable will be marked as
# "compatible with a non-executable stack" which the kernel
# will happily provide as such.
# A special section where GCC writes that the code can
# accommodate a non-executable stack. This is the normal case.
# Executable stacks are needed for some special usages (not standard C).
# On modern processors, the kernel can make a non-executable stack
# (a stack which triggers an exception if someone tries to execute
# as code some data which is on the stack); this is viewed by
# some people as a "security feature" because putting code on the stack
# is a common way to exploit buffer overflows.
END.
