[M3devel] Problem interfacing C lib

[Dragiša Durić]

Here are procedures I am binding. No nonsense, no #define hell. Clear and pure, and I don't see how I would write better and clearer :).

=====
struct evbuffer_ptr
evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start)
{
        return evbuffer_search_range(buffer, what, len, start, NULL);
}

struct evbuffer_ptr
evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start, const struct evbuffer_ptr *end)
{
   
On Mar 21, 2012, at 5:35 AM, Jay K wrote:

> That is a bit wierd.
> Lots of things seem wierd at first..and wierd even at second,
> but often there are reasons things are how they are,
> and often there are barriers to change.
> 
>  
> I would expect Ctypes.char = CHAR.
>  
> 
> But I don't know why it isn't.
>  
>  
> I realize that CHAR ideally is some idealized abstract thing that can hold a unicode character.
> But it isn't. It is 8 bits and will never be larger.
>  
>  
> You are really best not to interface directly to C that you didn't write
> and the C that you write that you interface to, you are best restricting
> to a subset of C.
>  
> 
> And use m3-libs/m3core/src/unix for working examples.
>  
> 
> I remember when I added "BITS FOR" in Ctypes, it broke stuff.
> I either didn't commit that or later removed it, leaving things as they
> have been historically.
>  
>  
>  - Jay
> 
> > To: dabenavidesd at yahoo.es
> > Date: Tue, 20 Mar 2012 15:06:59 -0700
> > From: mika at async.caltech.edu
> > CC: m3devel at elegosoft.com
> > Subject: Re: [M3devel] Problem interfacing C lib
> > 
> > char_star is, at least in my installation
> > 
> > UNTRACED REF [-16_7f-1 .. 16_7f]
> > 
> > But it's a good point that it's not actually an UNTRACED REF ARRAY OF CHAR
> > 
> > However 
> > 
> > ADR(chars[0]) 
> > 
> > ought to be more or less precisely of the type char_star
> > 
> > ... so I doubt that is the problem.
> > 
> > I'm curious about whether the assembly code for the call changes without
> > the <*EXTERNAL*> pragma... it shouldn't should it? In which case, where
> > is chars passed, in pure Modula-3 code? I don't know enough about the
> > standard ABI of amd64 to know what the code should look like I'm afraid.
> > 
> > Mika
> > 
> > "Daniel Alejandro Benavides D." writes:
> > >Hi all:
> > >I think the unchecked error lays down to:
> > >Unsafe Operations section 2.7 (cf. Green Book SPWM3, p- 61):
> > >it's allowed to have " ... a value of type ADDRESS to be assigned to a vari=
> > >able of type UNTRACED REF T. It is an unchecked runtime error if the value =
> > >does not address a variable of type T."
> > >
> > >which could be reads conversely as:
> > >
> > >a value of type UNTRACED REF T to be assigned to a variable of type ADDRESS=
> > >. It is a checked runtime error if the variable does not address a var=
> > >iable of type .T=20
> > >=20
> > >And because because char_star is a subrange [-128 .. 127] OF INTEGER (and n=
> > >ot ADDRESS) and chars is UNTRACED REF ARRAY OF CHAR erro is cf. the specif=
> > >ication.
> > >So maybe you need to change your char_star
> > >
> > >Thanks in advance
> > >
> > >
> > >--- El mar, 20/3/12, Dragi=C5=A1a Duri=C4=87 <dragisha at m3w.org> escribi=C3=
> > >=B3:
> > >
> > >> De: Dragi=C5=A1a Duri=C4=87 <dragisha at m3w.org>
> > >> Asunto: Re: [M3devel] Problem interfacing C lib
> > >> Para: "Mika Nystrom" <mika at async.caltech.edu>
> > >> CC: m3devel at elegosoft.com
> > >> Fecha: martes, 20 de marzo, 2012 01:04
> > >> Errorr is SIGSEGV.
> > >>=20
> > >> chars is UNTRACED REF ARRAY OF CHAR but it is lesser
> > >> problem, I think. It looks like formal 'what' is not
> > >> sent at all!? It's place is taken by next argument - INTEGER
> > >> len (equal 0x7 in this example).
> > >>=20
> > >> One common problem I meet often (as I bind C often :) is
> > >> this - address of open array argument is ot what it looks
> > >> like. To be sure you are getting address of various UNTRACED
> > >> REF..ARRAY.. and open array procedure arguments - use=20
> > >>=20
> > >> ADR(chars[0])
> > >>=20
> > >> and do not use:
> > >>=20
> > >> LOOPHOLE(chars, ADDRESS)
> > >>=20
> > >> Of course, I tried ADR(chars[0]) :) - Same thing happened.
> > >> Right now II downgraded my code to use strstr(3), but this
> > >> argument passing still bugs me.
> > >>=20
> > >> dd
> > >>=20
> > >>=20
> > >> On Mar 20, 2012, at 1:26 AM, Mika Nystrom wrote:
> > >>=20
> > >> > What are the declarations of all the variables involved
> > >> in the call?
> > >> >=20
> > >> > And what is the actual error? Is it a SIGBUS,
> > >> SIGSEGV?
> > >> >=20
> > >> > =3D?utf-8?Q?Dragi=3DC5=3DA1a_Duri=3DC4=3D87?=3D writes:
> > >> >> I had some error before I LOOPHOLEd it.
> > >> >>=20
> > >> >> On Mar 19, 2012, at 7:27 PM, Daniel Alejandro
> > >> Benavides D. wrote:
> > >> >>=20
> > >> >>> Hi all:
> > >> >>> if chars is ADDRESS type why are you
> > >> LOOPHOLE'ing it?=3D20
> > >> >>> Thanks in advance
> > >> >>> =3D20
> > >> >>> --- El lun, 19/3/12, Dragi=3DC5=3DA1a Duri=3DC4=3D87
> > >> <dragisha at m3w.org>
> > >> =3D
> > >> >> escribi=3DC3=3DB3:
> > >> >>> =3D20
> > >> >>>> De: Dragi=3DC5=3DA1a Duri=3DC4=3D87 <dragisha at m3w.org>
> > >> >>>> Asunto: [M3devel] Problem interfacing C
> > >> lib
> > >> >>>> Para: "m3devel" <m3devel at elegosoft.com>
> > >> >>>> Fecha: lunes, 19 de marzo, 2012 12:13
> > >> >>>> #1 0x00000035bd8172a0 in
> > >> >>>> evbuffer_search_range (buffer=3D3D0x694090,
> > >> what=3D3D0x7 <Address
> > >> >>>> 0x7 out of bounds>, len=3D3D0,
> > >> start=3D3D0x0,
> > >> >>>> end=3D3D0x7fffffffdbb0)
> > >> >>>> at buffer.c:2441
> > >> >>>> #2 0x0000000000404a0c in
> > >> Buffer__Search (t=3D3D<error
> > >> >>>> reading variable>, pattern=3D3D<error
> > >> reading
> > >> >>>> variable>, from=3D3D<error reading
> > >> variable>,=3D20
> > >> >>>> to=3D3D<error reading
> > >> variable>) at
> > >> >>>> ../src/Buffer.m3:150
> > >> >>>> =3D20
> > >> >>>> Buffer.m3:150
> > >> >>>> pos :=3D3D
> > >> >>>> evbuffer.search_range(t.b, LOOPHOLE(chars,
> > >> ADDRESS), len,
> > >> >>>> NIL, NIL);
> > >> >>>> =3D20
> > >> >>>> t.b is a pointer, so is chars=3DE2=3D80=3DA6 len
> > >> is Utypes.size_t and
> > >> >>>> it's value is 7.
> > >> >>>> =3D20
> > >> >>>> <* EXTERNAL evbuffer_search_range *>
> > >> >>>> PROCEDURE search_range(buf: t; what:
> > >> char_star; len: size_t;
> > >> >>>> start, end: UNTRACED REF ptr): ptr;
> > >> >>>> =3D20
> > >> >>>> t is an ADDRESS, and so on=3DE2=3D80=3DA6
> > >> >>>> =3D20
> > >> >>>> Critical Mass Modula-3 version d5.9.0
> > >> >>>> last updated: 2010-07-21
> > >> >>>> compiled: 2010-10-04 07:24:16
> > >> >>>> configuration: /etc/cm3.cfg
> > >> >>>> host: AMD64_LINUX
> > >> >>>> target: AMD64_LINUX
> > >> >>>> =3D20
> > >> >>>> =3D20
> > >> >>>> Any ideas? TIA,
> > >> >>>> dd
> > >> >>>> =3D20
> > >> >>>> =3D20
> > >>=20
> > >>

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