Some C(atexit and on_exit) and Assembly Examples

main.c

// about atexit and on_exit: https://www.gnu.org/software/libc/manual/html_node/Cleanups-on-Exit.html

#include <stdio.h>
void byebye();
void seeyouagain();
int main()
{
    void *p = NULL;
    atexit(byebye);
    on_exit(seeyouagain, p);
    //printf("Hello World");

    return 0;
}

void byebye()
{
  //printf("\nBye bye~\n");
}
void seeyouagain()
{
  //printf("\nWant see you again.~\n");
}

makefile

all: main
start.o:
	@echo "----------Compile ASM----------"
	nasm -f elf64 start.asm -o start.o
main.o:
	@echo "----------Compile C------------"
	gcc -c main.c -o main.o
main: start.o main.o
	@echo "----------LINK OBJ(will error)------------"
	@echo "----------not stisfy----------------------"
	ld main.o start.o /usr/lib/x86_64-linux-gnu/libc.a
clean:
	rm -fr main.o start.o

start: start.o
	ld start.o -o start

start.asm

global _start

section .data
start_str: db  "Start Program\n", 0
start_len: equ $-start_str

section .text
_start:
    mov     edx,start_len
    mov     ecx,start_str
    mov     ebx,1
    mov     eax,4
    int     0x80