Re: Import a type from C

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

"Frank J. Lhota" <NOSPAM.lhota.adarose@verizon.net> writes:

>     pragma Convention( C, My_Data );
> 
> The Convention pragma can be used to specify that this record type should be
> laid out in the same way that a C compiler would. 

Note that "a C compiler" really means "the C compiler that the Ada
compiler knows about, with its default command line args". For
example, GNAT will assume Gnu C, _without_ -fpacked. ObjectAda
probably assumes MS C, again without the "packed" flag. That has
caused me some major problems, when linking against C code compiled
_with_ the -fpacked flag.

So I always use a rep spec, instead of relying on Convention (C). Then
I write some C code that checks the struct size, to be sure there is
no padding.

-- 
-- Stephe