Dynamic source code in C++ [closed]

Answer 1

You could embed a C/C++ interpreter into your program if you really need this. However, you could also embed a more script-like language instead.

Answer 2

The real answer to your question is this:

extern "C" {
void function1 ();
void function2 ();
void function3 ();
}


 int main (int argv, char * argv [])
 {
     char * myString = new char [100];
     ...
     myString = "function1"; //user input     

     void (*f)() = dlsym(RTLD_NEXT, myString);
     f();
 }

You can obtain the function defined in your binary (by its name, if it was declared with extern "C"), and call it.

On windows, it becomes uglier, but still possible - read on GetProcAddress

Answer 3

To answer your question of how this is usually done, the answer is: it isn't.

Having to use something like eval() is usually a design problem. If you really do need it, embed a scripting language such as Lua or Python.

Answer 4

If you put function1 .. functionN in a DLL, you could simply pull them out and invoke them by name using dlopen/dlsym which would probably get you 90% of the way you want to go.

Answer 5

I would build an array, or an STL list, of function pointers and the strings that you find that trigger the call to them. If you really need to call an arbitrary function you should investigate RTTI http://en.wikipedia.org/wiki/Run-time_type_information

Answer 6

how do I declare an array of pointers to functions?

The C programmer's response to this question:

use cdecl.

cdecl> declare functable as pointer to function (int,pointer to int) returning double

double (*functable)(int , int *)

cdecl> declare functable as array 17 of pointer to function (int) returning double

double (*functable[17])(int )

Note that functions automatically convert into pointers to functions, in the same sense that arrays decay into pointers. You don't need an & to take the address of a function to put it in a pointer.

If you're in C++, it might help to use a std::map<YourFunctionPointerType> instead of an array, since you want to map strings anyway...

The OO approach:

Use polymorphism instead. It doesn't immediately solve your problems, but there's a good chance that if you're doing this it makes sense to have a class for each function.

Note that a vtable is, fundamentally, a table of pointers to functions.