扩展动态链接共享库？ [英] Extend a dynamic linked shared library?

问题描述

我是新的C，我的知识的缺乏很抱歉（我这里C-书真的是巨大的：）

I'm new at C, so sorry for my lack of knowledge (my C-book here is really massive :)

我想延长与封闭源代码的共享库（libcustomer.so），但公众所知的API。

I would like to extend a shared library (libcustomer.so) with closed source, but public known api.

是这样的可能吗？

1. 重命名为libcustomer.so liboldcustomer.so


2. 创建一个扩展的共享库libcustomer.so（以便其他人含蓄地使用扩展的）


3. 链接liboldcustomer.so到我的扩展libcustomer.so通过-loldcustomer


4. 直接转发任何额外的未实现的方法到老liboldcustomer.so

我不认为它会工作方式（姓名被编译到。所以，不是吗？）。
但是，什么是另类？

I don't think it would work that way (the name is compiled into the .so, isn't it?). But what's the alternative?

有关＃4：有没有做到这一点的一般方式，还是我写了一个名为像旧的方法，并调用转发（如何？）

For #4: is there a general way to do this, or do I have to write a method named like the old one and forward the call (how?)?

由于原libcustomer.so（= liboldcustomer.so）可随时更改，所有的东西应该动态地工作。

Because the original libcustomer.so (=liboldcustomer.so) can change from time to time, all that stuff should work dynamically.

有关安全方面的原因，我们的系统没有LD_ preLOAD（否则我会采取:(）。

For security reasons, our system has no LD_PRELOAD (otherwise I would take that :( ).

想想扩展验证的检查和放大器;一些更好的NPE-装卸。

Think about extended validation-checks & some better NPE-handlings.

在此先感谢您的帮助！

编辑：

我只是执行我的扩展如图所示的答案，但我都不得不时刻与一个未处理的情况：

I'm just implementing my extension as shown in the answer, but I have one unhandled case at the moment:

我如何代理了从扩展库结构？

How can I "proxy" the structs from the extended library?

例如我有这样的：

customer.h：

customer.h:

struct customer;

customer.c：

customer.c:

struct customer {
    int children:1;
    int age;
    struct house *house_config;
};

现在，在我的客户extension.c我写的​​所有的公共方法形成customer.c，但我怎么直通的结构？

Now, in my customer-extension.c I am writing all the public methods form customer.c, but how do I "pass-thru" the structs?

您的时间和放大器非常感谢;帮助！

Many thanks for your time & help!

推荐答案

所以，你必须用OldLib

So you have OldLib with

void func1();
int  func2();
... etc

步骤4可能看起来像一些静态初始化创建另一个库。

The step 4 might look like creating another library with some static initialization.

与内容创建NewLib：

Create NewLib with contents:

void your_func1();

void (*old_func1_ptr)() = NULL;
int  (*old_func2_ptr)() = NULL;

void func1()
{
    // in case you don't have static initializers, implement lazy loading
    if(!old_func1_ptr)
    {
       void* lib = dlopen("OldLibFileName.so", RTLD_NOW);
       old_func1_ptr = dlsym(lib, "func1");
    }

    old_func1_ptr();
}

int func2()
{
    return old_func2_ptr();
}

// gcc extension, static initializer - will be called on .so's load
// If this is not supported, then you should call this function
// manually after loading the NewLib.so in your program.
// If the user of OldLib.so is not _your_ program,
// then implement lazy-loading in func1, func2 etc. - check function pointers for being NULL
// and do the dlopen/dlsym calls there.
__attribute__((constructor))
void static_global_init()
{
   // use dlfcn.h
   void* lib = dlopen("OldLibFileName.so", RTLD_NOW);

   old_func1_ptr = dlsym(lib, "func1");
   ...
}

的 static_global_init 和所有的 func_ptr 的可能，如果你有旧的API的一些描述来自动生成。创建NewLib后，你当然可以更换OldLib。

The static_global_init and all the func_ptr's can be autogenerated if you have some description of the old API. After the NewLib is created, you certainly can replace the OldLib.

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