Re: [Jack-Devel] packed data structures in jack2

On Thu, Jul 19, 2012 at 11:41 AM, Basil Nutmeg <
[hidden]> wrote:

On Thu, Jul 19, 2012 at 06:54:41AM +0200, Stéphane Letz wrote:
> > The point to pack memory is to allow a 64 bits server to be used with 32
> bits clients or the contrary. Since shared memory is going to be used by
> "both sides", the only safe way we found was to use packed memory struct.
>
> Ah, thanks, I see now. I see how putting packed on everything does make
> this easier. However, it also makes the code unusable on some platforms
> and slow on others. Would you be open to alternative approaches here? I'd
> be willing to do some work to help out


 [ ... ]


>
> /* ... this type has the same layout between 32-bit and 64-bit. */
> struct A_with_alignment {
>   aligned_char x;
>   aligned_int64_t i;
> };
>

this translates to:

     struct A_with_alignment {
          char     x    __attribute__((aligned(sizeof(char));
          int64_t i     __attribute__((aligned(sizeof(int64_t));
      };

which i think is not the same as what "packed" does at all. it could be
enough though, and arguably is better because it preserves aligned access.

however, as stephane noted: far easier to just change the macros that do
this stuff so that they are no-ops.


> As another idea would be to have a source file which simply includes all
> the important headers and is compiled with -Wpadded and maybe even
> -Werror, to catch any mistakes.
>

i don't this is portable to non-gnu compilers. i could be wrong.

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