World: r3wp

I think I understand what you think, but I got lost in translation 
:-) I will have to think about it few times and try to do some experiments.Thank 
for putting some time into the topic ...

I understand the first two steps, but I don't understand, how such 
a function wrapper in Red/System would look like ...

Here's an example from the C library binding:

on-quit: function [  ; Register handler for normal program termination.
;	handler		[function! []]  ; Callback
	handler		[integer!]
	return:		[logic!]
][
	#either OS = 'Syllable [
		not as-logic _on-quit handler none none
	][
		not as-logic _on-quit handler
	]
]

Instead of passing the handler, you'd execute it directly

hmm, as I am not loading the library myself (IIRC R2 had something 
like addres-of), but Red/System is doing so. I wonder, if there is 
a way of how actually get the library handle ...

hmm, I have installed PE Explorer. It can somehow display some DLL 
related info. In export table, I can see functions entry points. 
If I understand it correctly, those will be an offsets from address, 
to which the library is bound after loading?

Basically, but that's not the method used when loading manually

If you can find the functions you need in there, it shouldn't be 
necessary to load them manually. If so, something else keeps your 
functions from working

If they're not in the list, that would explain why they don't work, 
because the manual loading is needed to pull them in at run time

Besides GetProcAddress, there's a set of a few function for loading 
libraries and symbols. You'd need to bind them and use them to load 
the library, which yields the library handle, and then load the functions. 
They're what load/library and make routine! in REBOL use

Not sure if the Windows symbol tables work like I said, so you'll 
have to try

Hm, I'm not sure either if the wrapper function can currently be 
written like I said. You'd have to use the specific declaration as 
function! type for the function pointer, but the Red/System type 
checker may not currently support getting the function pointer in 
the right type

Hmm, so in my case the situation in Red/System is even worse than 
possibly in R2 and World, where I could get such a handle from load/library 
directive, whereas in Red/System, what you describe, is writing completly 
separate layer. In fact, C's LoadLibrary is not difficult to handle, 
but still - a C level coding, which I thought is almost eliminated 
for wrapping purposes ...

All in all, if it's possible to load the functions manually, it should 
also be possible to import them at load time with the regular #import 
method. So something else may be wrong in the binding

The Red/System situation is certainly not worse: it's the other way 
around. You can program manual loading with just a few well defined 
functions, the same that R2 and World use. But normally, you use 
automatic loading by the operating system, which is the standard 
and most efficient way to do it, and which R2 and World can't use 
because they execute bindings at run time

It's just that there is no ready binding for manual loading that, 
so you currently have to program it yourself

loading yet

This is the code from LEDSet program:

bool LoadLedCtrl(void)
{
	g_hLedCtrlInst = LoadLibrary("LedCtrl.dll");
	if (!g_hLedCtrlInst)
	{
		g_hLedCtrlInst = LoadLibrary("..\\LedCtrl.dll");
		return false; 
	}
	//

 fpIsPower		= (LSN_ISPOWER)GetProcAddress(g_hLedCtrlInst, "LSN_IsPower");

So, if I would wrap LoadLibrary and GetProcAddress, I could get what 
you describe? :-)

See, the library handle comes from the standard library loading function 
(well, Windows standard)

Yes, that would make your binding work the same way as the C code, 
so if that doesn't work, you definitely know the problem is elsewhere

Can you show your complete #import specification and the definition 
of a function that doesn't work?

#import [

   "LedCtrl.dll" cdecl [

      led-is-power?: "LSN_IsPower" [
         return: [logic!]
      ]

      led-open-card: "LSN_OpenCard" [
          return: [logic!]
      ]  

      led-get-screen-number: "LSN_GetLedScrNumb" [
          return: [integer!]
      ]

      led-set-power: "LSN_Power" [
         power-on? [logic!]
         return: [logic!]
      ]

      led-get-brightness: "LSN_GetBright" [
         return: [integer!]
      ]

led-get-brightness is the first one to fail ...

your lib uses stdcall, so better use stdcall instead of cdecl (though 
that's most likely not the culprit here)

I used that, I changed it later to give it a try ...

rest looks good to me, at first glance

just to be sure: in the code example from the LEDSet program you 
gave earlier, is there maybe some initialisation function called 
_after_ all the proc addrs have been retrieved?

there is plenty of ASSERT(fpIsPower		!= NULL);, for each funcitons, 
then function LoadLedCtrl returns true ...

well, I am bothering you here more, than if I would upload somewhere 
a project file with all sources. The app is really small, but I might 
be missing some obvious setting or something else :-)

An initialisation function is indeed a good candidate for the problem

http://xidys.com/pekr/ledset-source.zip

It's not that obvious, the C code does strange indirections :-)

Kaj - so I defined following functions. It returns something :-) 
Hopefully I have an integer handle, representing the "address"? of 
the requested function. Now is the last step you described - how 
should I invoke it?

   "Kernel32.dll" stdcall [

      load-library: "LoadLibraryA" [
         name [c-string!]
         return: [integer!]
      ]
       
      get-proc-address: "GetProcAddress" [
         library-handle [integer!]
         function-name  [c-string!]
         return: [integer!] 
       ]

   ]

print ["load-library: " handle: load-library "LedCtrl.dll" lf]

print ["get-proc-address: " get-proc-address handle "LSN_IsPower" 
lf]

led-power?: function [
	handler		[function! [return: [logic!]]]
	return:		[logic!]
][
	handler
]

led-power? as function! get-proc-address handle "LSN_IsPower"

Something like that, but I'm not sure the casting to function! type 
will be accepted

get-proc-address should really be defined as return: [function!] 
but that's not currently supported

*** Compilation Error: invalid definition for function led-power?: 
[function! [return: [logic!]]]

Ah, that's only supported in import functions, I think. That's why 
I handle them as integers everywhere, but then you can't call it 
as a function. So game over

I will return to serial communication decoding, although that's not 
much fun :-)

Some Red/System type casting will not help? :-)

No, because those casts aren't supported yet

Anyway - it was a good way to learn a few bits in a practical manner 
:-)

I can't find anything in the C++ code, though, that would necessitate 
manual loading. It looks like the regular #import should work. What 
errors are you getting exactly from those functions?

*** Runtime Error 99: unknown error
*** at: 7572FC56h

Doc may need to have a look at it

R2 and World crash. In fact I think that those functions just try 
to write to serial port ...

If R2 and World crash the same way, manual loading doesn't help