.
├── main
│ └── main.c
└── shapes
├── include
│ └── shapes.h
└── shapes.c
4 directories, 3 files
shapes 文件夹是一个平面图形计算库，可计算矩形，圆形的面积和周长。
// include/shapes.h
#ifndef SHAPES_H
#define SHAPES_H
// 定义矩形结构体
typedef struct {
double length;
double width;
} Rectangle;
// 定义圆形结构体
typedef struct {
double radius;
} Circle;
// 计算矩形的面积
double calculateRectangleArea(Rectangle rectangle);
// 计算矩形的周长
double calculateRectanglePerimeter(Rectangle rectangle);
// 计算圆形的面积
double calculateCircleArea(Circle circle);
// 计算圆形的周长
double calculateCirclePerimeter(Circle circle);
#endif
// shapes.c
#include "shapes.h"
#include <math.h>
// 计算矩形的面积
double calculateRectangleArea(Rectangle rectangle) {
return rectangle.length * rectangle.width;
}
// 计算矩形的周长
double calculateRectanglePerimeter(Rectangle rectangle) {
return 2 * (rectangle.length + rectangle.width);
}
// 计算圆形的面积
double calculateCircleArea(Circle circle) {
return M_PI * circle.radius * circle.radius;
}
// 计算圆形的周长
double calculateCirclePerimeter(Circle circle) {
return 2 * M_PI * circle.radius;
}
main 文件夹是一个二进制可执行库，用于测试平面图形计算库
// main.c
#include <stdio.h>
#include "shapes.h"
int main() {
Rectangle rectangle = {5.0, 3.0};
Circle circle = {4.0};
printf("Rectangle Area: %lf\n", calculateRectangleArea(rectangle));
printf("Rectangle Perimeter: %lf\n", calculateRectanglePerimeter(rectangle));
printf("Circle Area: %lf\n", calculateCircleArea(circle));
printf("Circle Perimeter: %lf\n", calculateCirclePerimeter(circle));
return 0;
}
创建平面图形计算库的静态链接库 Link to heading
进入平面图形计算库根路径
cd shapes/
.
├── include
│ └── shapes.h
└── shapes.c
2 directories, 2 files
生成目标文件（shapes.o）：
gcc -c -o shapes.o shapes.c -I include/
.
├── include
│ └── shapes.h
├── shapes.c
+└── shapes.o
2 directories, 3 files
生成静态链接库（libshapes.a）：
ar rcs libshapes.a shapes.o
.
├── include
│ └── shapes.h
+├── libshapes.a
├── shapes.c
└── shapes.o
2 directories, 4 files
创建平面图形计算库的动态链接库 Link to heading
进入平面图形计算库根路径
cd shapes/
.
├── include
│ └── shapes.h
└── shapes.c
2 directories, 2 files
生成动态链接库（libshapes.so）：
gcc -shared -o libshapes.so -fPIC shapes.c -I include/
.
├── include
│ └── shapes.h
+├── libshapes.so
└── shapes.c
2 directories, 3 files
使用静态链接库 Link to heading
进入二进制可执行库根路径
cd main/
.
└── main.c
1 directory, 1 file
编译可执行文件并链接静态库
gcc -o main main.c -L ../shapes/ -l shapes -I ../shapes/include/
.
+├── main
└── main.c
1 directory, 2 files
运行可执行文件
$ ./main
Rectangle Area: 15.000000
Rectangle Perimeter: 16.000000
Circle Area: 50.265482
Circle Perimeter: 25.132741
查看可执行文件的动态链接库依赖关系以及它们的搜索路径
$ ldd ./main
linux-vdso.so.1 (0x00007ffe598e8000)
libc.so.6 => /lib64/libc.so.6 (0x00007f3cb171b000)
/lib64/ld-linux-x86-64.so.2 (0x00007f3cb1914000)
使用动态链接库 Link to heading
进入二进制可执行库根路径
cd main/
.
└── main.c
1 directory, 1 file
编译可执行文件并链接动态库
gcc -o main main.c -L ../shapes/ -l shapes -I ../shapes/include/
.
+├── main
└── main.c
1 directory, 2 files
添加动态链接库的搜索路径
export LD_LIBRARY_PATH=../shapes/
Info
也可以在编译可执行文件的时候通过 -Wl,-rpath 参数直接指定运行库路径，这样就不需要额外添加动态链接库的搜索路径
gcc -o main main.c -I ../shapes/include/ -Wl,-rpath, ../shapes/libshapes.so
查看可执行文件的动态链接库依赖关系以及它们的搜索路径
$ ldd ./main
linux-vdso.so.1 (0x00007ffd778ab000)
+ ../shapes/libshapes.so (0x00007f1526be8000)
libc.so.6 => /lib64/libc.so.6 (0x00007f15269f1000)
/lib64/ld-linux-x86-64.so.2 (0x00007f1526bef000)
运行可执行文件
$ ./main
Rectangle Area: 15.000000
Rectangle Perimeter: 16.000000
Circle Area: 50.265482
Circle Perimeter: 25.132741
查看可执行文件的动态链接库依赖关系以及它们的搜索路径
$ ldd ./main
linux-vdso.so.1 (0x00007ffc98260000)
+ libshapes.so => ../shapes/libshapes.so (0x00007f4f8efeb000)
libc.so.6 => /lib64/libc.so.6 (0x00007f4f8edf4000)
/lib64/ld-linux-x86-64.so.2 (0x00007f4f8eff2000)
运行可执行文件的同时打印动态链接库的搜索信息
$ LD_DEBUG=libs ./main
151250: find library=libshapes.so [0]; searching
151250: search path=../shapes/glibc-hwcaps/x86-64-v3:../shapes/glibc-hwcaps/x86-64-v2:../shapes (LD_LIBRARY_PATH)
151250: trying file=../shapes/glibc-hwcaps/x86-64-v3/libshapes.so
151250: trying file=../shapes/glibc-hwcaps/x86-64-v2/libshapes.so
151250: trying file=../shapes/libshapes.so
151250:
151250: find library=libc.so.6 [0]; searching
151250: search path=../shapes/glibc-hwcaps/x86-64-v3:../shapes/glibc-hwcaps/x86-64-v2:../shapes (LD_LIBRARY_PATH)
151250: trying file=../shapes/glibc-hwcaps/x86-64-v3/libc.so.6
151250: trying file=../shapes/glibc-hwcaps/x86-64-v2/libc.so.6
151250: trying file=../shapes/libc.so.6
151250: search cache=/etc/ld.so.cache
151250: trying file=/lib64/libc.so.6
151250:
151250:
151250: calling init: /lib64/ld-linux-x86-64.so.2
151250:
151250:
151250: calling init: /lib64/libc.so.6
151250:
151250:
151250: calling init: ../shapes/libshapes.so
151250:
151250:
151250: initialize program: ./main
151250:
151250:
151250: transferring control: ./main
151250:
Rectangle Area: 15.000000
Rectangle Perimeter: 16.000000
Circle Area: 50.265482
Circle Perimeter: 25.132741
151250:
151250: calling fini: [0]
151250:
151250:
151250: calling fini: ../shapes/libshapes.so [0]
151250:
151250:
151250: calling fini: /lib64/libc.so.6 [0]
151250:
151250:
151250: calling fini: /lib64/ld-linux-x86-64.so.2 [0]
151250:
Question
当同名的动态链接库和静态连接库在同一目录时，会优先链接哪个？
进入平面图形计算库根路径
cd shapes/
.
├── include
│ └── shapes.h
+├── libshapes.a
+├── libshapes.so
├── shapes.c
└── shapes.o
2 directories, 5 files
进入二进制可执行库根路径
cd main/
.
└── main.c
1 directory, 1 file
链接平面图形计算库
gcc -o main main.c -L ../shapes/ -l shapes -I ../shapes/include/
.
+├── main
└── main.c
1 directory, 2 files
查看可执行文件的动态链接库依赖关系以及它们的搜索路径
$ ldd main
linux-vdso.so.1 (0x00007ffc24b27000)
+ libshapes.so => ../shapes/libshapes.so (0x00007f7350c14000)
libc.so.6 => /lib64/libc.so.6 (0x00007f7350a1d000)
/lib64/ld-linux-x86-64.so.2 (0x00007f7350c1b000)
Note
优先链接动态链接库