Re: [Jack-Devel] JACK 1.9.10 to test (for 64/32 bits compatibility)

On 7 Jan 2013, at 15:50, Stéphane Letz wrote:

> 
> Not yet on master, but on a development branch
> 

Okay, I found it.  Sadly it doesn't compile with MSVC.  The reason is the use of the sizeof operator.  For example, the declaration for type 'jack_double' evaluates to this for MSVC:-

        typedef __declspec(align(sizeof(double))) double jack_double;

and the problem is that sizeof() isn't evaluated by the preprocessor (it gets evaluated later) so the alignment size is unknown at this point.

In any case, I'm not sure how this strategy leads to portable struct packing (or to put it another way, it might be working in the ARM compiler but I suspect it's probably working by accident).  Different structs (and even the fields within a struct) will have different alignment.  Of course, that's theoretically do-able - but it seems unlikely that the ARM compiler could make sense of this complicated, variable packing arrangement whilst at the same time, failing to understand 1-byte packing.

Are we sure that __attribute__((__packed__)) isn't just broken in the ARM compiler?  That seems the most likely explanation for what Robin observed.

John

1357584835.23472_0.ltw:2,RSa <BC88F349-313C-44FD-B08E-2B33267E9BD7 at tiscali dot co dot uk>