[squeak-dev] FFI | How to call a function that expects a "long" argument in C?

Marcel Taeumel marcel.taeumel at hpi.de
Wed Jun 10 09:20:05 UTC 2020

Hi Nicolas,

good idea! I just did that.

https://stackoverflow.com/questions/49784522/how-one-supports-both-32-and-64-bits-target-in-squeak-ffi [https://stackoverflow.com/questions/49784522/how-one-supports-both-32-and-64-bits-target-in-squeak-ffi]

https://stackoverflow.com/questions/49784253/how-one-deals-with-multiple-pointer-level-like-char-in-squeak-ffi [https://stackoverflow.com/questions/49784253/how-one-deals-with-multiple-pointer-level-like-char-in-squeak-ffi]

https://stackoverflow.com/questions/49783882/how-one-deals-with-typedefs-in-squeak-ffi [https://stackoverflow.com/questions/49783882/how-one-deals-with-typedefs-in-squeak-ffi]

https://stackoverflow.com/questions/49783126/how-one-defines-a-union-type-in-squeak-ffi [https://stackoverflow.com/questions/49783126/how-one-defines-a-union-type-in-squeak-ffi]

https://stackoverflow.com/questions/49782651/how-one-aligns-structure-fields-in-squeak-ffi [https://stackoverflow.com/questions/49782651/how-one-aligns-structure-fields-in-squeak-ffi]

Am 09.06.2020 22:42:03 schrieb Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:

Le mar. 9 juin 2020 à 22:39, Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com [mailto:nicolas.cellier.aka.nice at gmail.com]> a écrit :

Le mar. 9 juin 2020 à 19:19, Marcel Taeumel <marcel.taeumel at hpi.de [mailto:marcel.taeumel at hpi.de]> a écrit :

Hi, there.

I want to understand how data models for 64-bit influence the image side of Squeak FFI.
https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models [https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models]

I discovered that there are test functions in the SqueakFFIPrims plugin (sqFFITestFuncs.c) that expect actual "long" types. So, I assume that that is the "long" from C, not Squeak FFI, and thus different on 64-bit Windows vs. 64-bit Unix.




ffiTestMixedDoublesAndLongs (!!!)

Only the last one is actually called from FFI Tests, which could be worse. Because there is not yet a mechanism in place that considers the data model an 64-bit platforms.

So, I think that an atomic type alias for such a C "long" argument could be defined like this:

(wordSize = 4 or: [platformName = 'Win32'])
   ifTrue: ['long' "meaning 'int' in the plugin]
   ifFalse: ['longlong']

BTW, I documented as I discovered in a serie of SO questions like

I'm on a poor man hp sucking touchpad... Give me back my Mac!

https://stackoverflow.com/questions/49784522/how-one-supports-both-32-and-64-bits-target-in-squeak-ffi [https://stackoverflow.com/questions/49784522/how-one-supports-both-32-and-64-bits-target-in-squeak-ffi]

Feel free to add new answers for updated FFI when ready.

Yet, I have no clue on how to name such a type alias. long_t ? native_long_t ? Squeak FFI's 'long' is already taken, and it is always 4 byte.

Me neither... c_long?

Would it make sense to also query the data model through a primitive and add that to FFIPlatformDescription? LLP64, LP64, ILP64, SILP64, ... 


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