C++ dlopen使用

C++ dlopen使用 Loading Functions

Loading Functions

In C++ functions are loaded just like in C, with dlsym. The functions you want to load must be qualified as extern “C” to avoid the symbol name being mangled.

Example 1. Loading a Function

main.cpp:

#include
#include <dlfcn.h>

int main() {
using std::cout;
using std::cerr;

cout << "C++ dlopen demo\n\n";// open the library
cout << "Opening hello.so...\n";
void* handle = dlopen("./hello.so", RTLD_LAZY);if (!handle) {cerr << "Cannot open library: " << dlerror() << '\n';return 1;
}// load the symbol
cout << "Loading symbol hello...\n";
typedef void (*hello_t)();
hello_t hello = (hello_t) dlsym(handle, "hello");
if (!hello) {cerr << "Cannot load symbol 'hello': " << dlerror() <<'\n';dlclose(handle);return 1;
}// use it to do the calculation
cout << "Calling hello...\n";
hello();// close the library
cout << "Closing library...\n";
dlclose(handle);

}

hello.cpp:

#include

extern “C” void hello() {
std::cout << “hello” << ‘\n’;
}
链接class;
main.cpp:

#include “polygon.hpp”
#include
#include <dlfcn.h>

int main() {
using std::cout;
using std::cerr;

// load the triangle library
void* triangle = dlopen("./triangle.so", RTLD_LAZY);
if (!triangle) {cerr << "Cannot load library: " << dlerror() << '\n';return 1;
}// load the symbols
create_t* create_triangle = (create_t*) dlsym(triangle, "create");
destroy_t* destroy_triangle = (destroy_t*) dlsym(triangle, "destroy");
if (!create_triangle || !destroy_triangle) {cerr << "Cannot load symbols: " << dlerror() << '\n';return 1;
}// create an instance of the class
polygon* poly = create_triangle();// use the class
poly->set_side_length(7);cout << "The area is: " << poly->area() << '\n';// destroy the class
destroy_triangle(poly);// unload the triangle library
dlclose(triangle);

}

polygon.hpp:

#ifndef POLYGON_HPP
#define POLYGON_HPP

class polygon {
protected:
double side_length_;

public:
polygon()
: side_length_(0) {}

void set_side_length(double side_length) {side_length_ = side_length;
}virtual double area() const = 0;

};

// the types of the class factories
typedef polygon* create_t();
typedef void destroy_t(polygon*);

#endif

triangle.cpp:

#include “polygon.hpp”
#include

class triangle : public polygon {
public:
virtual double area() const {
return side_length_ * side_length_ * sqrt(3) / 2;
}
};

// the class factories

extern “C” polygon* create() {
return new triangle;
}

extern “C” void destroy(polygon* p) {
delete p;
}

There are a few things to note when loading classes:

You must provide both a creation and a destruction function; you must not destroy the instances using delete from inside the executable, but always pass it back to the module. This is due to the fact that in C++ the operators new and delete may be overloaded; this would cause a non-matching new and delete to be called, which could cause anything from nothing to memory leaks and segmentation faults. The same is true if different standard libraries are used to link the module and the executable.The destructor of the interface class should be virtual in any case. There might be very rare cases where that would not be necessary, but it is not worth the risk, because the additional overhead can generally be ignored.If your base class needs no destructor, define an empty (and virtual) one anyway; otherwise you will have problems sooner or later; I can guarantee you that. You can read more about this problem in the comp.lang.c++ FAQ at http://www.parashift.com/c++-faq-lite/, in section 20.

链接:
http://www.faqs.org/docs/Linux-mini/C+±dlopen.html

C++ dlopen使用相关推荐

System.err: java.lang.UnsatisfiedLinkError: dlopen failed: library “libc++_shared.so“ not found
Android Studio 配置OpenCV 的时候出现这样的提示黄色警告libc++_shared.so" not found : System.err: java.lang.Unsa ...
c语言获取文件名的相对路径,c – 如何获取对应于给予dlopen的相对路径的绝对库文件名？...
在我的程序中,我有如下代码 /* libname may be a relative path */ void loadLib(char const *libname) { void *handle ...
分析Android ：java.lang.UnsatisfiedLinkError: dlopen failed * is 32-bit instead of 64-bit
Crash 日志: java.lang.UnsatisfiedLinkError: dlopen failed: "/data/data/com.ireader.plug.sdk/iread ...
关于android 5.0报错:dlopen failed: couldn't map ... Permission denied
问题描述: 我的应用当中集成了一个安全相关的sdk,而这个sdk中使用的so是加过壳的. 它加载native so的方式是:Java System.loadLibrary --> native ...
dlopen failed: library “libopencv_java4.so“ not found 解决
dlopen failed: library "libopencv_java4.so" not found Android studio编译yolov5时报错, 最后解决方法: a ...
用g++编译生成动态连接库*.so的方法及连接(dlopen() dlsym() dlclose())
================================================================ //test_so_file.h ifndef TEST_SO_FIL ...
【Android 逆向】Android 进程注入工具开发 ( 注入代码分析 | 获取 linker 中的 dlopen 函数地址并通过远程调用执行该函数 )
文章目录一.dlopen 函数简介二.获取目标进程 linker 中的 dlopen 函数地址三.远程调用目标进程 linker 中的 dlopen 函数一.dlopen 函数简介 dlo ...
【Android 逆向】Android 进程注入工具开发 ( EIP 寄存器指向 dlopen 函数 | ESP 寄存器指向栈内存 | 调试程序收回目标进程控制权 )
文章目录一.EIP 寄存器指向 dlopen 函数二.ESP 寄存器指向栈内存三.调试程序收回目标进程控制权一.EIP 寄存器指向 dlopen 函数代码段中 , 一般都有 dlopen 函 ...
【错误记录】NDK 动态库报错 ( dlopen failed: file offset for the library /lib/arm64/libwebp.so“ ＞= file size:0)
文章目录一.报错信息二.解决方案一.报错信息运行 NDK 时 , 删除了引用的动态库 , 然后 " Ctrl + Z " 恢复 , 运行就报如下错误 ; 2021-04-2 ...
采用dlopen、dlsym、dlclose dlopen dlerror加载动态链接库【总结】
1.前言为了使程序方便扩展,具备通用性,可以采用插件形式.采用异步事件驱动模型,保证主程序逻辑不变,将各个业务已动态链接库的形式加载进来,这就是所谓的插件.linux提供了加载和处理动态链接库的系统调 ...

C++ dlopen使用

C++ dlopen使用 Loading Functions

C++ dlopen使用相关推荐

最新文章

热门文章