[Vm-dev] [squeak-dev] valid pragma syntax

[Nicolai Hess]

2016-01-12 20:57 GMT+01:00 Esteban Lorenzano <estebanlm at gmail.com>:

>
> well… UnifiedFFI, UFFI or whatever it will be called already does that… as
> you know.
> Currently we are using “older” NB way: as a method call, then solving it
> in first call. This is nice because is compatible and easies some stuff.
> But final objective is to provide a pragma and solve it in compilation
> time.
>
> Then we can 100% deprecate the invalid pragma old FFI uses today.
>

But how do we solve the issue?


>
> At least, that’s what we have talk :)
>
> Esteban
>
> On 12 Jan 2016, at 20:06, Nicolai Hess <nicolaihess at gmail.com> wrote:
>
>
>
> 2016-01-10 16:57 GMT+01:00 Eliot Miranda <eliot.miranda at gmail.com>:
>
>>
>> Hi Nicolai,
>>
>> On Sun, Jan 10, 2016 at 3:16 AM, Nicolai Hess <nicolaihess at gmail.com>
>> wrote:
>>
>>> pharo fogbugz issue: 17359 MessageNotUnderstood: receiver of "keywords"
>>> is nil
>>>
>>>
>>> is this valid pragma syntax:
>>>
>>>     <apicall: bool 'SetCursorPos' (long long) module: 'user32.dll'>
>>>
>>
>> As others have said this is not a valid pragma.  A valid pragma is a
>> message expression (a message with no receiver) that has only literal
>> arguments.  There is one exception, to accept a variable name for the error
>> code in a primitive invocation.
>>
>> And as Levente has said it is a goal of the new FFI to get rid of the old
>> syntax you show above.
>>
>
>
> Thanks Eliot.
>
> I think I will wait what Esteban will say to this, he put those classes in
> the image, maybe he had a plan for the new ffi/apicall syntax
>
>
>
>> And as Igor Stasenko discovered /any/ C signature can be written as a
>> literal Array, providing we allow underscores in Symbols (which is a
>> preference).  So for example, the heapsort declaration from the standard C
>> library:
>>
>> int
>>      heapsort(void *base, size_t nel, size_t width,
>>          int (*compar)(const void *, const void *))
>>
>> could be written as a pragma via e.g.
>>
>>     <ffiCCall: #(int heapsort(void *base, size_t nel, size_t width, int
>> (*compar)(const void *, const void *)))>
>>
>> in which case it is equal to
>>
>>    <ffiCCall: #(#int #heapsort #( #void #* #base #, #size_t #nel #,
>> #size_t #width #, #int #( #* #compar ) #( #const #void #*, #const #void
>> #*)))>
>>
>> which, while a massive hack, is pretty neat.  The only difficulty in
>> parsing the above s that void *, is #void #*, not #void #* #,.
>>
>> So for me, the natural pragma syntax for the new FFI should be a single
>> keyword starting with ffi that includes the language with which to parse
>> the pragma's argument, followed by a literal Array containing the signature
>> (rather than e.g. a String).  I'd also provide a special-purpose
>> pretty-printer for literal arrays that would be used to pretty-print the
>> above, e.g. when decompiling.
>>
>> This would easily allow extensions such as
>>
>>      <ffiCcall: #(wchar_t * wcschr(const wchar_t *s, wchar_t c)) arg1is:
>> #UnicodeString arg2is: Character>
>>
>> to guide a marshalling engine in providing automatic checks and
>> conversions.
>>
>> [Slightly OT]
>> Note that I'm already using this syntax in Alien callbacks because one
>> thing it does is to normalize the signature, eliminating the significance
>> of most whitespace (the #*, above being one example where it fails).  So a
>> Callback for heapsort above looks like
>>
>> voidstarvoidstarRetint: callbackContext sp: spAlien
>> <signature: #(int (*)(const void *, const void *)) abi: #IA32>
>> ^callbackContext wordResult:
>> (block
>> value: (Alien forPointer: (spAlien unsignedLongAt: 1))
>> value: (Alien forPointer: (spAlien unsignedLongAt: 5)))
>>
>> or
>> voidstarvoidstarRetintARM32: callbackContext sp: spAlien
>> <signature: #(int (*)(const void *, const void *)) abi: #ARM32>
>> ^callbackContext wordResult:
>> (block
>> value: (Alien forPointer: (spAlien registerAt: 1))
>> value: (Alien forPointer: (spAlien registerAt: 2)))
>>
>>
>> Hmmm, if Callback had subclasses for each ABI then the above would become
>>
>> IA32Callback methods for signature
>> voidstarvoidstarRetint: callbackContext sp: spAlien
>> <signature: #(int (*)(const void *, const void *))>
>> ^callbackContext wordResult:
>> (block
>> value: (Alien forPointer: (spAlien unsignedLongAt: 1))
>> value: (Alien forPointer: (spAlien unsignedLongAt: 5)))
>>
>> ARM32Callback methods for signatures
>> voidstarvoidstarRetint: callbackContext sp: spAlien
>> <signature: #(int (*)(const void *, const void *))>
>> ^callbackContext wordResult:
>> (block
>> value: (Alien forPointer: (spAlien registerAt: 1))
>> value: (Alien forPointer: (spAlien registerAt: 2)))
>>
>> Much nicer.  I shall make it so.
>>
>> our (pharo) parser can not parse this (does not recognizes the
>>> "selector parts" (apicall:module:) right)
>>>
>>> Any recommendations how to fix this
>>> - fix RBParser or
>>> - change this pragma, for example, like this
>>>   <apicall: #(bool SetCursorPos (long long)) module: 'user32.dll'>
>>>
>>>
>>> nicolai
>>>
>>
>> _,,,^..^,,,_
>> best, Eliot
>>
>>
>
>
>
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