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C++ Dynamic Shared Library on Linux
I am writing a shared object say libtest.so which has a class and a function. I have another program say "Program.cpp" from which i want to call the class and its function present in the libtest.so file. I am clueless as to how to proceed. Please help.
Thanks Regards Mahesh
Dynamically, you need to call dlsym to get the address of the function, and then call it through the pointer. The syntax for this is a bit tricky, since dlsym returns a void*, and there's no conversion between void* and a pointer to function. (Some compilers do allow it, although formally, in pre C++11, it required a diagnostic, as does the C standard.) The solution recommended in the Posix standard is:
int (*fptr)( int ); *(void**)(&fptr) = dlsym( handle, "function_name" ); This supposes that pointers to functions have the same size and format as pointers to data—not guaranteed by the C or C++ standards, but guaranteed by Posix.
dlsym to get the address of the object (a straight-forward cast from void* will do here), and call the function on it: MyType* p = (MyType*)dlsym(...); p->function();
dlopen), or statically? In the latter case just add-ltestto yourld.