知识点

知识点2

知识点3

实例

//a.cc == main.cc
#include <iostream>
#include "b.h"

int main()
{
    bbb();
    std::cout << "Hello world" << std::endl;
    return 0;
}

//b.h-----
#pragma once

void bbb();

//b.cc-----
#include <iostream>
#include "ccc.h"

void bbb()
{
    ccc();
    std::cout << "Hello world" << std::endl;
}

// ccc.h-----
#pragma once
void ccc();

// ccc.cc-----
#include <iostream>

void ccc()
{
    std::cout << "Hello world" << std::endl;
}

编译过程1

$ g++ -fPIC -shared ccc.cc -o libccc.so
$ g++ -fPIC -shared b.cc -o libbbb.so -L. -lccc
# g++ a.cc -L. -lb 是不行的，具体看https://blog.csdn.net/zrq293/article/details/105969423
g++ a.cc -L. -lb -Wl,--copy-dt-needed-entries
/usr/bin/ld: warning: libccc.so, needed by ./libb.so, not found (try using -rpath or -rpath-link)
$ g++ a.cc -L. -lb -Wl,--copy-dt-needed-entries,-rpath-link=.
$ ./a.out
./a.out: error while loading shared libraries: libb.so: cannot open shared object file: No such file or directory
$ g++ a.cc -L. -lb -Wl,--copy-dt-needed-entries,-rpath-link=.,-rpath=.
tiantian@DESKTOP-UVN3KRD:~/code$ ./a.out
./a.out: error while loading shared libraries: libccc.so: cannot open shared object file: No such file or directory

$ ldd a.out
        linux-vdso.so.1 (0x00007ffff5585000)
        libb.so => ./libb.so (0x00007f44961f0000)
        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f4495fc0000)
        libc.so => ./libc.so (0x00007f4495fb0000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4495d80000)
        libccc.so => not found
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f4495c80000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f4496215000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f4495c60000)
$ export LD_LIBRARY_PATH=.
$ ./a.out
Hello world
Hello world
Hello world

cmake的扩展