[Pharo-users] C struct in 32 bits vs 64 bits VM

April 19, 2018

      I try to understand differences between 32 bits and 64 bits FFI support for
C structures.

I build a class called MyStruct subclass of FFIExternalStructure.
and define a layout for this structure like this one :

MyStruct class>>fieldsDesc
    "self rebuildFieldAccessors"

    ^ #(
        int index ;)

and then I generate automatically the field accessors.

If I use a 32 bit VM, the following method is generated to access the index
field :

index
    "This method was automatically generated"
    ^handle signedLongAt: OFFSET_INDEX

and if I use a 64 bits VM, the same method is generated ...

I'm a bit puzzled because, if sizeof(int) = sizeof(long) in a 32 bits VM,
they have different for 64 bits VM (sizeof(int) = 4 and sizeof(long) = 8).

Someone to explain me or this is a bug ?

âThank you.â

-- 
Serge Stinckwich
UMI UMMISCO 209 (SU/IRD/UY1)
"Programs must be written for people to read, and only incidentally for
machines to execute."http://www.doesnotunderstand.org/