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

Esteban Lorenzano estebanlm at gmail.com
Tue Jan 12 20:22:56 UTC 2016


> On 12 Jan 2016, at 21:12, Nicolai Hess <nicolaihess at gmail.com> wrote:
> 
> 
> 
> 2016-01-12 20:57 GMT+01:00 Esteban Lorenzano <estebanlm at gmail.com <mailto: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?

Well, we should add an #visitFFIPragmaNode: who can deal with it, in the mean time :)

Esteban

>  
> 
> At least, that’s what we have talk :)
> 
> Esteban
> 
>> On 12 Jan 2016, at 20:06, Nicolai Hess <nicolaihess at gmail.com <mailto:nicolaihess at gmail.com>> wrote:
>> 
>> 
>> 
>> 2016-01-10 16:57 GMT+01:00 Eliot Miranda <eliot.miranda at gmail.com <mailto:eliot.miranda at gmail.com>>:
>>  
>> Hi Nicolai,
>> 
>> On Sun, Jan 10, 2016 at 3:16 AM, Nicolai Hess <nicolaihess at gmail.com <mailto: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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