Re: Interfacing between Ada and C: records and structs

[awdorrin <awdorrin@gmail.com>]

This is code from the POSIX Florist API for Ada. There is a comment in the code that says that the 'Dummy' tagged null record is:
 "to force by-reference parameter mode"

Your test code matches up with similar code I wrote on my system, except being 32-bit I get D as "range 0 .. 31"

The 'rep' files generated by -gnatR3s for the Florist POSIX API gives:
for DUMMY'Size use 32;
for DUMMY'Alignment use 4;
for DUMMY use record
   _TAG at 0 range  0 .. 31;
end record;

for MUTEX'Object_Size use 256;
for MUTEX'Value_Size use 224;
for MUTEX'Alignment use 8;
for MUTEX use record
   MUTEX at  0 range  0 .. 191;
   D     at 24 range  0 .. 31;
end record;


So at least I understand why it isn't 192 bits, but 256.