On 12 April 2018 at 16:00, Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com> wrote:

>
>
> 2018-04-12 3:10 GMT+02:00 Eliot Miranda <eliot.miranda at gmail.com>:
>
>> Hi Nicolas,
>>
>> On Wed, Apr 11, 2018 at 2:23 PM, Nicolas Cellier <
>> nicolas.cellier.aka.nice at gmail.com> wrote:
>>
>>> I'm trying to see how hard it is to port my HDF5 work from VW to Squeak.
>>> It was not a pleasure in VW, because that already raised some questions
>>> despite that there is a somehow detailed DLLCC manual:
>>>
>>> https://stackoverflow.com/questions/49544642/why-cant-i-pass
>>> -an-uninterpretedbytes-to-a-void-thru-dll-c-connect
>>> https://stackoverflow.com/questions/49564024/isnt-pointer-ty
>>> pe-checking-disabled-in-dll-c-connect-and-is-that-ok
>>>
>>
>> What are you actually trying to do?  Can you post the C definitions?  I'm
>> very familiar with both the SqueakFFI and DLLCC (as of 7.4.1) and the basic
>> differences are to do with DLLCC's better cross-platform support, in that
>> it auto-redefines typedefs on load.  But other than that I think the
>> SqueakFFI is either just as good, or in some cases better (e.g. DLLCC has a
>> bug in that it is the actual parameter that carries detailed type
>> information for a struct, whereas in Andreas' SqueakFFI it is, correctly,
>> the formal parameter).
>>
>> Hi Eliot,
> the library is huge (HDF5).
> All the interfacing code is available at cincom public store (HDF5 bundle)
> To get an idea, you can inspect a clone of HDF5 library at
> https://github.com/live-clones/hdf5/tree/develop/src
> The main structures/enum/typedefs/prototypes are in the H5*public.h files
>
> The problems are all exposed in SO questions, but I can try and priotitize.
>
> The essential barrier is that those headers use almost exclusively
> typedef'ed types.
> Library is too huge for manual subsitution; this must be mechanized.
> I would prefer some kind of support in FFI rather than having to hack own
> fragile ad-hoc pre-processor.
>

Maybe more of a distraction than a help, but browsing around because its an
interesting topic,
some discoveries...
*
https://eli.thegreenplace.net/2012/12/17/dumping-a-c-objects-memory-layout-with-clang
* https://github.com/rpav/c2ffi
* http://blog.llvm.org/2018/03/dragonffi-ffijit-for-c-language-using.html
* https://github.com/marianopeck/FFICHeaderExtractor

cheers -ben



>
> Then I have a problem because of alignment of struct fields which is
> compact in Squeak FFI rather than conforming to platform conventions.
> Same here, manually hacking with field size is a no go, this must be
> mechanized.
>
> Then some unions are used too and there is no support at all in FFI.
>
> Then definitions like size_t are dependent on machine word size (32 or 64
> bits), and there is no support for that in FFI.
> I'll have to duplicate some work for supporting both 32 and 64 bits
> Squeak, or explore new hacks...
> But there is no support and no documentation (how to).
>
> Then while digging in source coden I did not see any double pointer
> support in struct fields.
> The example I provide on SO shows what I would qualify as a bug.
> I don't know yet whether I'll need those, but it's not good.
>
> Maybe I can shoot each problem with more or less ugly workarounds.
> At the end i can declare void * and deal with offset directly, but that's
> both:
> - a lot of work
> - a good recipe for generating very hard to find bugs - crashes if lucky,
> silent corruption if not
>  (dealing with offsets is like writing in assembler instead of C)
>
> Given the size of the library, the probability of not creating such fault
> in manual translation is 0%
> Plus, there are a few evolutions from one version of the library to the
> other...
>
> That's my definition of hard++
>
>
>>
>>>
>>>
>>> But in Squeak, it sounds like hard++:
>>>
>>> https://stackoverflow.com/questions/49782651/how-one-aligns-
>>> structure-fields-in-squeak-ffi
>>> https://stackoverflow.com/questions/49783126/how-one-defines
>>> -a-union-type-in-squeak-ffi
>>> https://stackoverflow.com/questions/49783443/how-one-defines
>>> -a-fixed-size-array-member-in-a-struct-in-squeak-ffi
>>> https://stackoverflow.com/questions/49783882/how-one-deals-w
>>> ith-typedefs-in-squeak-ffi
>>> https://stackoverflow.com/questions/49784253/how-one-deals-w
>>> ith-multiple-pointer-level-like-char-in-squeak-ffi
>>> https://stackoverflow.com/questions/49784522/how-one-support
>>> s-both-32-and-64-bits-target-in-squeak-ffi
>>>
>>> Either I'm blind, or the very light documentation that I found lacks
>>> those details
>>> http://wiki.squeak.org/squeak/2426
>>>
>>> I think that I could throw a few more questions (dealing with enums...)
>>> but I don't want to excede some unknown quota and start irritating a touchy
>>> SO moderator ;)
>>>
>>> I'm afraid that there is no answer but "you're on your own"...
>>> I'm open to studying Alien or UnifiedFFI of Pharo.
>>> Or I can try and improve FFI.
>>> At this stage, my trajectory has already been quite perturbed, and
>>> despite my knowledge of rocket science, I can see that I'm not going to put
>>> HDF5 on the intended orbit :(
>>>
>>> Thoughts?
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> _,,,^..^,,,_
>> best, Eliot
>>
>>
>>
>>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.squeakfoundation.org/pipermail/squeak-dev/attachments/20180412/647f1917/attachment.html>