patchelfの挙動確認するのに使った色々

compose.yml

services:
  task:
    build:
      context: .
      dockerfile: Dockerfile.patchelfpoc
    tty: true
    stdin_open: true
    working_dir: /working_dir
    command: /bin/bash
    volumes:
      - ./src:/working_dir

Dockerfile.patchelfpoc

FROM debian:bookworm

RUN apt-get update
RUN apt-get install -y gcc g++ make software-properties-common curl wget vim patchelf file
RUN apt-get clean && rm -rf /var/lib/apt/lists/*

CMD ["/bin/bash"]

main.c

void func();

int main() {
  func();

  return 0;
}

Makefile

build:
	gcc -c -o main.o main.c
	gcc -fPIC -shared -o libmylib1.so mylib1.c
	gcc -fPIC -shared -o libmylib2.so mylib2.c
	gcc -o main main.c -L. -lmylib1 -Wl,-rpath,.

link2:
	patchelf --add-needed ./libmylib2.so main

read:
	readelf -d main

mylib1.c

#include <stdio.h>

void func(void) {
  printf("Hello World!\n");
}

mylib2.c

#include <stdio.h>

void func(void) {
  printf("Bye World!\n");
}