[solved] HookEntry style stub for C++ class method

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Sat, 2015-08-29 21:16

salass00

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Last seen: 1 year 2 months ago

Joined: 2011-02-03 11:27

[solved] HookEntry style stub for C++ class method

What I want to do is make a HookEntry style stub function that calls a method specified by pointer in hook->h_SubEntry on an object instance also specified by pointer in hook->h_Data.

This is the test code I've written for this so far:

#include <utility/hooks.h>
 
class MyClass {
	ULONG func1(APTR obj, APTR msg);
	ULONG func2(APTR obj, APTR msg);
	ULONG func3(APTR obj, APTR msg);
};
 
typedef ULONG (MyClass::*MyClassHookMethod)(APTR, APTR);
 
ULONG MyClassHookEntry(struct Hook *hook, APTR obj, APTR msg) {
	MyClass *instance = (MyClass *)hook->h_Data;
	MyClassHookMethod method = (MyClassHookMethod)hook->h_SubEntry;
	return (*instance.*method)(obj, msg);
}

Unfortunately for some reason g++ does not seem to like my casting of h_SubEntry to MyClassHookMethod. I can't really understand why though as their both pointer types.

The error g++ gives me is this:

hooktest.cpp: In function ‘ULONG MyClassHookEntry(Hook*, APTR, APTR)’:
hooktest.cpp:13:54: error: invalid cast from type ‘ULONG (*)() {aka long unsigned int (*)()}’ to type ‘MyClassHookMethod {aka long unsigned int (MyClass::*)(void*, void*)}’
  MyClassHookMethod method = (MyClassHookMethod)hook->h_SubEntry;
                                                      ^

Any ideas how to solve this?

I could also use friend functions for the hooks but I would rather avoid that if possible...

Sat, 2015-08-29 21:46

salass00

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Last seen: 1 year 2 months ago

Joined: 2011-02-03 11:27

Re: HookEntry style stub for C++ class method

Just found that sizeof() on MyClassHookMethod returns a size of 8 bytes so apparently it's more than just a simple pointer as I originally thought. In that case I will just need to use an extended Hook structure to fit the extra data in and problem solved.

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