OpenEuphoria

RE: stdcall / cdecl -- please clarify

• Posted by Andy Serpa <renegade at earthling.net> Feb 12, 2002
• 620 views

Matthew Lewis wrote:
> 
> 
> Andy Serpa wrote:
> > Regarding the problem with calling functions using cdecl in 
> > .dll files:
> > 
> > I am not a C programmer, so this is not completely clear to me.  Will 
> > the corruption/errors only occur when using the Translator?  If I use 
> > the interpreter with these .dll's, do I have no worries?
> 
> You'll have this problem in Eu regardless.  Every Eu call is stdcall.
>  

Hmmm... that means that even though the interpreter "luckily" can handle 
these things, it means we are on shaky ground for a number of powerful C 
libraries:  the Regex library that I noted a while back, and also the 
SQL-Lite (I can't remember the exact name) library.  I would love to be 
using those, but this issue makes me wary -- plus I want to be able to 
translate to C for distribution, which definitely doesn't work.


> > Can this problem be gotten around by using the Translator with Watcom 
> > for my Euphoria programs, or is it the .dll that needs to be 
> > altered?  
> > (I believe the latter, but I'm not positive.)
> > 
> > Would it be possible to make a simple "intermediate" C 
> > program or .dll 
> > that is called with stdcall, which then in turn calls the 
> > desired .dll 
> > using cdecl?  In other words, my Euphoria program calls a 
> > function in a 
> > .dll using stdcall.  That fuction calls the 2nd .dll  using cdecl.  
> > Would this slow things down?
> 
> I've done something similar by wrapping a dll with another, hand coded c 
> dll
> that simply passes the calls through using cdecl.  It should be fairly 
> easy
> to implement, assuming a little bit of c knowledge.
> 

My knowledge of C is next to nothing.  But I think maybe some bright 
person around here could possibly make a "universal" dll wrapper where 
you could pass the name of the "final" dll, the name of the function & 
the arguments to the euMiddleMan (There.  Now the project even has a 
name.), which would in turn call that function using cdecl, get any 
return values, and then return those back to the Euphoria program.  This 
could even support a variable number of arguments.  Anybody want to 
tackle it?

I could do it myself, but I'd have to learn C first, so it would take a 
while.

OR -- maybe Euphoria itself could support this in the future?  It seems 
we are missing out on a lot of fast & powerful existing code over a 
relatively minor issue...


> And then Euman wrote:
> > This is an intersting subject and one Im struggling with aswell.
> > I tried to use a method presented by Matt Lewis on a cdecl .dll
> > and it doesnt work still if the .dll is designed for call_backs to
> > your program. Im guessing this might have something to do with
> > non-reintrant Euphoria. I just dont know.
> 
> So you implemented the asm I posted, and had the dll call the asm which
> called your function?  Can you tell me what happened?  I haven't had a
> chance to test any of that (just know that it works for stdcall).  Maybe
> I'll work up a little DLL and dissasemble it to get an idea for how 
> cdecl
> code looks.  Looking at the code I posted before, I'm sure that there's 
> more
> messing with the stack early on.  I think I can rework both pieces of 
> asm to
> call/be called by cdecl.
> 

If I could get this working on the regex and sql C libs I noted above, 
I'd be happy for the time being...


Andy Serpa
renegade at earthling.net