Best Way: _cdecl to _stdcall | Forex Factory

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Best Way: _cdecl to _stdcall

  • #1
  • First Post: Edited 5:51am Sep 20, 2011 3:20am | Edited 5:51am
Thanks.


anyone knows how this would be correctly done using extern


PHP Code
void _SomeFunction(int someint)
int _SomeFunction2(int a, int b)
I did it manually like:
PHP Code
MT4_EXPFUNC void __stdcall SomeFunction(int someint)
  {
  _SomeFunction(someint);
  return;
}




__Thanks__ MJ
  • #2
  • Edited 5:28am Sep 20, 2011 5:15am | Edited 5:28am
You make a wrapper dll (like you did) that wraps every function into a stdcall function or you use mt5/mql5 which can (from what have read 2 years ago¹) directly import cdecl functions. There is no way to use them directly from mql4.

______
¹ I have read this somewhere while mql5 was still in the planning phase, they might have changed this, I have never used mql5.
  • #3
  • Sep 20, 2011 9:52am Sep 20, 2011 9:52am
I have encountered a number of issues which I'm not sure how they are correctly handled.

Maybe someone knows thanks for any hints.


1.
_cdecl implementation: Not sure how to handle the 3 ... as I guess this are for any additional arguments
Object* Format(Object *exception, const char *format, ...)
PHP Code

MT4_EXPFUNC Object* __stdcall Format(Object *exception, const char *format, ...) {
    Object* e = Format(exception, format, ...);

    return(e);
}
2.
_cdecl implementation: Not sure how to handle this at all
int Call(int (*func)(void *), void *arg)

PHP Code
MT4_EXPFUNC int __stdcall Call(int (*func)(void *), void *arg) {
    int i = Call(int (*func)(void *), arg);

    return(i);
}
3. UNSURE with the return void* (it compiles but is it ok to do it like this?
_cdecl implementation:
void* MemMalloc(size_t n)

PHP Code
MT4_EXPFUNC void* __stdcall MemMalloc(size_t n) {
   void* is = Mem_Malloc(n);

    return(is);
}

I don't really need them but I came across them and would be interested how one does it correctly.


Thanks
__Thanks__ MJ
  • #4
  • Last Post: Edited 11:03am Sep 20, 2011 10:51am | Edited 11:03am
Quoting M_j
I don't really need them but I came across them and would be interested how one does it correctly.
It seems you are trying to wrap something more complicated.

Probably not everything that this dll exports can be used from mql4 or would even make sense (at least not in the exact same way how it would be used from C++). Functions that return pointers to complicated structs or objects or pointers to other functions and all that stuff would not be of much use in your mql4 code. If you need them then put all the code that uses them into your wrapper dll (thereby making it a little bit more than just a thin wrapper) and export only a few simple to use functions that can be easily used from mql4.

Move as much of the mql4 code as possible/reasonable into your dll and design a simple API for the whole thing so that you don't have to jump through hoops on the mql4 side to use your dll. You have found the right balance if the API between mql4 and the dll is as simple (elegant) and easy as possible.
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