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

Marcel Taeumel marcel.taeumel at hpi.de
Tue Jun 9 17:19:16 UTC 2020

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']

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.

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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