Re: Help with Gnat Cross-compile

[Ara Kassabian <akass@worldnet.att.net>]

Samuel G. Williams wrote:
> 
> I am looking for good examples on two scenarios. The first is the compile of
> Ada code for later linking in C. I would also like any recommendations for call
> converntions. Second I am looking for the reverse. Being able to compile c
> then link in with Ada also with the calling conventions. I am currently
> attempting to help a friend without an Internet connection obtain this
> information. I would welcome all replies. BTW he is using GNAT on a Solaris
> workstation. He found brief entries in the GNAT UG but didn't quite
> understand them well enough to be useful.
> 
> Thanks in advance for your help.
> 

In Ada-83, interfacing with C was as easy as using the right pragmas, so long as
you didn't run into threading issues (both the C and Ada-83 parts of our program
were threaded, and the two threading packages were not aware of each other). It
*should* be just as easy with GNAT. The procedure should be:

1. Calling C from Ada: Write a package spec declaring the C functions and using
"pragma import", so Ada knows it needs to use C calling conventions.

2. Calling Ada95 from C: Write a header file with the Ada95 function/procedure
prototypes. If you cannot turn off name mangling in Ada95 using a pragma, then
you need to compile your files, figure out the mangled names by looking in the
object files and use those as your function names in your C header files. You
make things look pretty by using #define to create unmangled aliases for the
mangled functions. You *may* run into problems with Ada95 procedures. I am not
sure if they equate to void functions in C.

------------------------------------------------------
Ara Kassabian            akass@worldnet.att.net
                         akassabian@logicon.com (work)
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