OpenEuphoria

1. Problem calling my C DLL from a IDE created source

• Posted by Andrew Katz <Akatz712 at gmail.com> Mar 07, 2007
• 548 views

I have spent all day trying to figure out why my Euphoria windows program
cannot access my DLL. I have determined that in fact it does access it, but
that the arguments are passed wrong. So, I made a test case for this forum.

Here is my C code compiled with the Watcom C compiler and linked to a
Win32 NT DLL:

#if defined(__cplusplus)
#define EXPORTED extern "C" __declspec( dllexport )
#else
#define EXPORTED __declspec( dllexport )
#endif


EXPORTED int dll_entry( int arg )
{
	return (arg + arg);
}

------------

Here is the code from the IDE:

--  code generated by Win32Lib IDE v0.22.0 Build Dec-16-2006

constant TheProgramType="exw" 
 
include Win32lib.ew
without warning

--------------------------------------------------------------------------------
--  Window Window1
constant Window1 = createEx( Window, "Window1", 0, Default, Default, 400, 300,
0, 0 )
---------------------------------------------------------
--------------------------------------------------------------------------------
-- Test code in Window1 general

include dll.e -- this is for calling the dll written in C

atom dll
integer entry, garbage

dll = open_dll ("dlltest.dll")
entry = define_c_func (dll, "dll_entry_", {C_UINT}, C_UINT)
if entry = -1 then
    abortErr( "Function dll_entry not found" )
end if

garbage = c_func (entry,{5})
printf (1,"here is the value of 5+5 is %08x", garbage )





WinMain( Window1,Normal )
--this program has 33 lines without including this line. If there is a
discrepancy please send this file zipped to Judith.

Note: In order to make this find the function, I had to append a _ to the name.

Here is what happens when it is run:
A Console is generated by C:\EUPHORIA\bin\exw.exe

here is the value of 5+5 is 04000008

Note: global constant C_CHAR = #01000001,
                   C_UCHAR = #02000001,
                   C_SHORT = #01000002,
                  C_USHORT = #02000002,
                     C_INT = #01000004,
                    C_UINT = #02000004,

It seems as if the C_UINT value is being passed and not what I pass in c_proc.

Please tell me what I am doing wrong?
Thanks.

3. Re: Problem calling my C DLL from a IDE created source

• Posted by Andrew Katz <Akatz712 at gmail.com> Mar 07, 2007
• 502 views

Robert Craig wrote:
> 
> Andrew Katz wrote:
> > 
> > I have spent all day trying to figure out why my Euphoria windows program
> > cannot access my DLL. I have determined that in fact it does access it, but
> > that the arguments are passed wrong. 
> 
> You might have to specify the CDECL calling convention.
> 
>  From the documentation for define_c_func():
> 
>     "On Windows, you can add a '+' character as a prefix to the 
>      function name. This indicates to Euphoria that the function 
>      uses the cdecl calling convention. By default, Euphoria assumes 
>      that C routines accept the stdcall convention."
> 
> i.e.
> 
>     entry = define_c_func (dll, "+dll_entry_", {C_UINT}, C_UINT)
> 
> Regards,
>    Rob Craig
>    Rapid Deployment Software
>    <a href="http://www.RapidEuphoria.com">http://www.RapidEuphoria.com</a>

Adding the + had no effect. Should I try to compile the EUPHORIA language
myself and try to debug it?

5. Re: Problem calling my C DLL from a IDE created source

• Posted by Igor Kachan <kinz at peterlink.ru> Mar 07, 2007
• 514 views

Andrew Katz wrote:

[snip]

> Adding the + had no effect. Should I try to compile the EUPHORIA language
> myself and try to debug it?

Hi Andrew,

Your C test code:

-- #if defined(__cplusplus)
-- #define EXPORTED extern "C" __declspec( dllexport )
-- #else
-- #define EXPORTED __declspec( dllexport )
-- #endif

-- EXPORTED int dll_entry( int arg )
-- {
--      return (arg + arg);
-- }

is just equal the following Euphoria code:

global function dll_entry(integer x)
  return x+x
end function  

I've translated it using ecw.exe with
-wat -dll options and compiled with OW 1.4

Resulting Dll works Ok for me here, your test
program prints 00000010.

So I think, why not go this way?

DLL is yours one, you have C code,
Euphoria code is simple ...

Why not?

Then, maybe to compile your C code of your Dll
with options of make.bat, generated by ecw.exe?

I'm not a specialist in C/C++, so just my $0.02.

Regards,
Igor Kachan
kinz at peterlink.ru

7. Re: Problem calling my C DLL from a IDE created source

• Posted by Robert Craig <rds at RapidEuphoria.com> Mar 08, 2007
• 517 views

Andrew Katz wrote:
> I fixed this as follows:
> 
> The C program is:
> 
> int __stdcall __export _dll_entry( int arg )
> {
> 	return (arg + arg);
> }
> 
> And the change to the EU code is one line:
> 
> entry = define_c_func (dll, "__dll_entry@4", {C_UINT}, C_UINT)
> 
> -----------------
> 
> I do think this is a very strange way of doing things.
> For example, why does not dll_entry by itself work?

Windows dll's and the multiple C calling conventions are 
needlessly complicated and poorly documented, and aren't
fully compatible from one C compiler to the next.
Unfortunately Euphoria has to be able to interface
with these things. I think they add the "@4" part so
the C linker will know how many bytes of arguments
are to be passed.

> It is important to realize that this was just a test case. I have a long C
> procedure which I want to call and not rewrite.

You've won more than half the battle just by getting the interface
to work. What you do inside your C routine is your business
and should be relatively easy.

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com