Am Donnerstag, 26. Februar 2009 12:36 schrieb Magnus Therning:
Are there any guarantees here, or is it just me telling the compiler to please do what I say, but the compiler can decide not to follow my wishes?
I don't think there are guarantees, as the section ends with: "If a field cannot be unpacked, you will not get a warning, so it might be an idea to check the generated code with -ddump-simpl. See also the -funbox-strict-fields flag, which essentially has the effect of adding {-# UNPACK #-} to every strict constructor field." But it should be very likely to do what you want (of course, always compile with -O or -O2).
Is address aligning predictable?
Absolutely no idea, sorry.
I'm basically wondering if it'd be possible to to use this mechanism to avoid using FFI when reading data that basically is a dump of structs in a C program.
I doubt it, as I understand it, with {-# UNPACK #-}, you'll have the layout constuctor rawdata and the C structs won't have the constructor.
/M
Cheers, Daniel