Re: Calling C++ from within ADA

[Richard G. Hash <rgh@shell.com>]

In <CVANOVER.1.0007E49E@bamanet.ua.edu> CVANOVER@bamanet.ua.edu writes:
> Is there a way to call a C++ procedure from within ADA?
> I am using IBM AIX on an RS6000.

Unless I'm missing something you've got a link problem - both Ada
and C++ want control first (before main) for "elaboration" (and whatever
C++ calls it). A normal (AIX) C++ application uses /bin/xlC to link,
which actually creates a little tmp file with the cdtors table
in it, and links it in (you can see this being generated by munch if
you use "xlC -#").

You'll find that the crt0.o being linked in by C++ isn't the
one in /usr/lib/crt0.o, it's in /usr/lpp/xlC/lib/crt0.o, and it
has a call to "__C_runtime_startup()" in it.

We got around this by generating the ld script for the Ada program
(using an Ada main), and then linking in the generated cdtors
table and manually calling _C_runtime_startup () first thing
in our Ada main (we were linking in a C++ Dynatext library).

Yes, it's ugly; no, it's not portable; no, I can't even guarantee
it will always work (I just found _C_runtime_startup in crt0 and
said "hmm, looks suspicious, wonder what happens if you call it?").

If there is a cleaner solution then I would like to hear it (it took
me two months to convince Dynatext their library was in C++ (prior
versions were in C), and then all they said was "how about that?",
and didn't offer any solutions).

--
Richard G. Hash                                      email: rgh@shell.com
Shell Development Company, Bellaire Research Center  phone: (713) 245-7311
Member Team Ada                Free Ada94 compilers: cs.nyu.edu:/pub/gnat