[m-rev.] for review: implement pragma foreign_export

[Ian MacLarty]

On Wed, Jul 19, 2006 at 02:09:28PM +1000, Julien Fischer wrote:
> >>doc/reference_manual.texi:
> >>	Add a new section to the foreign language interface chapter
> >>	documenting the new pragma.
> >>
> >>	Update the descriptions of the language specific bindings to include
> >>	the new pragma.
> >>
> >>tests/hard_coded/Mmakefile:
> >>tests/hard_coded/pragma_foreign_export.{m,exp}:
> >>	Make sure that we can parse the new syntax and run a simple program
> >>	that uses exported procedures.
> >>
> >
> >Are you planning to replace all uses of ":- pragma export" in the
> >compiler (such as in browser/declarative_debugger.m) with the new pragma
> >in a subsequent diff?
> >
> 
> Not immediately.

But it seems that your diff has replaced ":- pragma export" with
":- pragma foreign_export" in error messages.  Will I get an error about
a ":- pragma foreign_export" now if I have an error in a ":- pragma
export"?  If so, then that's a bug.  I propose you fix that bug by
disallowing ":- pragma export" as soon as the new compiler has been
installed on our Mercury machines.

> >>Index: doc/reference_manual.texi
> >>===================================================================
> >>RCS file: /home/mercury1/repository/mercury/doc/reference_manual.texi,v
> >>retrieving revision 1.357
> >>diff -u -r1.357 reference_manual.texi
> >>--- doc/reference_manual.texi	5 Jul 2006 08:45:37 -0000	1.357
> >>+++ doc/reference_manual.texi	12 Jul 2006 08:05:27 -0000
> >>@@ -6071,6 +6071,9 @@
> >> 				       or function as a call to code
> >> 				       written in a different
> >> 				       programming language.
> >>+* Calling Mercury from foreign code::  How to call a Mercury predicate
> >>+                                       or funciton from a different
> >>+                                       programming language.
> >> * Using foreign types from Mercury::   How to use a type defined in
> >> 				       a different programming language
> >> 				       in Mercury code.
> >>@@ -6388,6 +6391,41 @@
> >>
> >> @c 
> >> -----------------------------------------------------------------------
> >>
> >>+ at node Calling Mercury from foreign code
> >>+ at section Calling Mercury from foreign code
> >>+
> >>+Mercury procedures may be exported so that they can be called by code
> >>written
> >>+in a foreign language.
> >>+
> >
> >I think you need to clarify that the foreign code that calls the Mercury
> >code must in turn have been called from Mercury code, or alternatively
> >the user needs to take steps to initialize the Mercury runtime before
> >calling the exported procedure.
> 
> Yes, but I'm not going to do that as a part of this diff.  Currently
> the only documentation we can point a user to for doing that is the 
> code in samples.  I'm planning to write a new section for the user's
> guide on initialising the runtime as part of the standalone libraries
> change - I'll update this section then.
> 

I still think it at least say that calling exported Mercury procedures
from foreign code that's not called from Mercury code originally is not
yet supported.  Reading the doc I'd expect to be able to call the
exported proc from my C program, but that won't work at the moment.

Ian.
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