OpenEuphoria

2. Re: Machine level exception with define_c_func()

• Posted by mic <micol972 at gmail.com> Dec 09, 2005
• 565 views

Without knowing the details about this particular DLL, shouldn't the allocate
function return a value (a pointer/handle to the resource), which also is the
input parameter to Free. Right now you have the Allocate function as a procedure
which pretty much makes it useless.

4. Re: Machine level exception with define_c_func()

• Posted by Craig Welch <craig at singmail.com> Dec 10, 2005
• 587 views

Al Getz wrote:

>>The last statement fails with "A machine-level exception occurred during 
>>execution of this statement".
>>
>>Given that I've never used any C functions from Euphoria, my first 
>>assumption is that I've put coded the c_func() or define_c_func() 
>>statements wrongly. But I've gone over them and over, and tried 
>>different types of C variables ... without any success.
>>
><snip>
>
>which for your code would look something like this:
>
>CONVERTER_Allocate = define_c_func(dll_handle, "CONVERTER_Allocate", {}
>,C_POINTER)
>CONVERTER_Free = define_c_func(dll_handle, "CONVERTER_Free", {C_POINTER}, 
>C_LONG)
>  
>

>atom ob
>ob=c_func(CONVERTER_Allocate,{})
>result=c_func(CONVERTER_Free, {ob})
>
>There's also a chance the free'er can be defined as a procedure instead of
>a function.
>
Thanks Al,

I've done that, and still get the failure "A machine-level exception 
occurred during execution of this statement"

I've also tried changing CONVERTER_Free to a procedure.

Time to ask the DLL owner, or any more thoughts from the Euphoria end?

I'm using an evaluation copy of the DLL, so I don't know that the owner 
will want to put any effort into supporting me at this stage. If I can 
get it working, I'm quite happy to pay him for a licence.

-- 
Craig

6. Re: Machine level exception with define_c_func()

• Posted by Bernie Ryan <xotron at bluefrog.com> Dec 10, 2005
• 584 views
• Last edited Dec 11, 2005

atom handle_ref
handle_ref = allocate(4)
poke4(handle_ref,handle)

if not c_func( CONVERTER_Free, {handle_ref} ) then  -- PASSED BY REFERENCE !!
  puts( 1, "Invalid converter handle!\n" )
end if

Bernie

My files in archive:
w32engin.ew mixedlib.e eu_engin.e win32eru.exw

Can be downloaded here:
http://www.rapideuphoria.com/cgi-bin/asearch.exu?dos=on&win=on&lnx=on&gen=on&keywords=bernie+ryan

8. Re: Machine level exception with define_c_func()

• Posted by Craig Welch <craig at singmail.com> Dec 11, 2005
• 563 views

Bernie Ryan wrote:

>if not c_func( CONVERTER_Free, {handle_ref} ) then  -- PASSED BY REFERENCE !!
>  puts( 1, "Invalid converter handle!\n" )
>end if
>
Well that fixed the problem for me!

Thanks DGuy for pointing out that my lack of understanding of the need 
for a handle, and my lack of realising that the '&' signified same.

In fact, I had looked through Bernie's w32.engin beginners.txt a few 
days ago, when I started this project, as there are some notes there on 
C interfacing. I obviously didn't pay enough attention, because there is 
a paragraph there that describes conventions such as '&Handle'.

Bernie, thanks for going to the trouble of adding that key bit of code 
that completely fixed the problem.

Now the machine exception makes perfect sense to me, as I was giving the 
DLL a what it thought was a reference to memory that was completely invalid.

I've done a few Euphoria projects now, and I think I'm beginning to get 
a better understanding of when I should just re-think and re-read to get 
the answer to a problem, and when I'm out of my depth and need to ask here.

Every time I've asked here, I've had the right answer within a day or 
two, and my knowledge of programming (generally, not just Euphoria) has 
increased dramatically.

The problem above helps validate my choice of Euphoria as the language 
in which to program. I'm sure glad I didn't choose one of the C variations!

Thanks again,

-- 
Craig