dlsym（）和dlopen（）在C ++中的替代方法 [英] Alternatives to dlsym() and dlopen() in C++

问题描述

我有一个应用程序的一部分使用共享库。这些库在编译时链接。


在运行时，加载器期望共享对象在 LD_LIBRARY_PATH 中，如果没有找到，整个应用程序崩溃，出现错误无法加载共享库。注意，不能保证客户端将有库，在这种情况下，我想让应用程序留下合适的错误消息，独立部分应该正常工作。

I have an application a part of which uses shared libraries. These libraries are linked at compile time.
At Runtime the loader expects the shared object to be in the LD_LIBRARY_PATH , if not found the entire application crashes with error "unable to load shared libraries".Note that there is no guarantee that client would be having the library, in that case I want the application to leave a suitable error message also the independent part should work correctly.

为此，我使用 dlsym（）和 dlopen（）共享库。问题是如果我有很多的API，我必须使用 dlsym（）和ptrs访问它们在我的情况下，导致内存损坏

For this purpose I am using dlsym() and dlopen() to use the API in the shared library. The problem with this is if I have a lot of functions in the API, i have to access them Individually using dlsym() and ptrs which in my case are leading to memory corruption and code crashes.

有任何替代方案吗？

推荐答案

你的问题的常见解决方案是声明一个函数指针表，做一个单一的dlsym（）来找到它，然后通过指向该表的指针调用所有其他函数。示例（未测试）：

The common solution to your problem is to declare a table of function pointers, to do a single dlsym() to find it, and then call all the other functions through a pointer to that table. Example (untested):

// libfoo.h
struct APIs {
   void  (*api1)(void);
   void *(*api2)(int);
   long  (*api3)(int, void *);
};

// libfoo.cc
void fn1(void) { ... }
void *fn2(int) { ... }
long fn3(int, void *) { ... }

APIs api_table = { fn1, fn2, fn3 };


// client.cc
#include "libfoo.h"
...
  void *foo_handle = dlopen("libfoo.so", RTLD_LAZY);
  if (!foo_handle) {
     return false;            // library not present
  }
  APIs *table = dlsym(foo_handle, "api_table");
  table->api1();              // calls fn1
  void *p = table->api2(42);  // calls fn2
  long x = table->api3(1, p); // calls fn3

使用dlsym和指针单独访问您的API函数本身不会导致内存损坏和崩溃。很可能你只是有错误。

P.S. Accessing your API functions individually using dlsym and pointers does not in itself lead to memory corruption and crashes. Most likely you just have bugs.

编辑：

你可以使用这个完全相同的技术与第三方库。创建 libdrmaa_wrapper.so 并将 api_table 添加到其中。将包装器直接链接到 libdrmaa.so 。

You can use this exact same technique with a 3rd-party library. Create a libdrmaa_wrapper.so and put the api_table into it. Link the wrapper directly against libdrmaa.so.

在主可执行文件中， dlopen libdrmaa_wrapper.so，RTLD_NOW）。如果（而且只有） libdrmaa.so 在运行时出现，并且提供您使用的所有API函数，此 dlopen 在 api_table 中。如果它成功，单个 dlsym 调用将允许您访问整个API。

In the main executable, dlopen("libdrmaa_wrapper.so", RTLD_NOW). This dlopen will succeed if (and only if) libdrmaa.so is present at runtime and provides all API functions you used in the api_table. If it does succeed, a single dlsym call will give you access to the entire API.

这篇关于dlsym（）和dlopen（）在C ++中的替代方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！