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!standard B.5 (00)          99-09-24 AI95-00204/02
!class binding interpretation 99-09-24
!status work item 99-02-02
!status received 98-03-27
!priority High
!difficulty Medium
!subject Interfaces.Fortran must be absent, right?
!summary
Interface packages such as Interfaces.Fortran may be provided independently of whether the implementation supports the interfacing pragma for that language. This applies also to other foreign languages including C and COBOL.
!question
Is it permitted to provide a package Interfaces.Fortran even if pragma convention Fortran is not supported? (Yes.)
!recommendation
(See summary.)
!wording
Replace the first sentence of B.2(12) which states
"For each implementation-defined convention identifier, there should be a child package of package Interfaces with the corresponding name."
by
"A child package of package Interfaces with the name of a convention may be provided irrespective of whether the convention is supported by the pragma Convention."
!discussion
There are two primary reasons for interfacing to another language such as Fortran. One is to access data in the conventions of that language and the other is to call code written in that language.
Ada provides two techniques for such interfacing. One is the pragma convention with appropriate parameter and the other is the existence of packages such as Interfaces.Fortran.
It is the intention that either or both of these techniques may be provided independently for a given language. Thus the package Interfaces.Fortran provides types that are sufficient for interfacing as stated by B.5(2) irrespective of whether the pragma Convention is supported for Fortran.
This is in apparent contradiction to B.2(12) which seems to imply that an interface package can only be provided if the corresponding pragma Convention is supported.
Similar rules apply to other foreign languages.
!corrigendum B.02(12)
Replace:
For each implementation-defined convention identifier, there should be a child package of package Interfaces with the corresponding name.
by:
A child package of package Interfaces with the name of a convention may be provided irrespective of whether the convention is supported by the pragma Convention.
!ACATS test
This is a permission to do something, so it is untestable by itself. The underlying features are throughly tested by the ACATS.
!appendix

!section B.5(00)
!subject interfaces.fortran must be absent, right?
!reference AARM-B.5
!from Samuel T. Gregory 98-03-19
!reference 1998-15830.a Samuel T. Gregory 1998-3-19>>
!discussion

Because of a lack of a FORTRAN compiler, and lack of (scheduled) time to
get FORTRAN unconstrained array parameters right before scheduling an
AVF, we were not going to claim to interface to FORTRAN, then someone
here typed in INTERFACES.FORTRAN and checked it into our runtime. Now,
instead of getting an error on the "with Interfaces.Fortran" lines of
CXB50042 and CXB50052, we get other errors later on.

Please confirm that INTERFACES.FORTRAN must actually be absent in order
for an implementation not to claim to interface to FORTRAN and not have
the FORTRAN acvc tests apply. Or tell us the real criteria.

Ivan's reasoning follows:

 - B.5(20) requires us to support convention FORTRAN for a
   FORTRAN-eligible type.
 - B.1(14-18) defines a FORTRAN-eligible type as one that either is, or
   has only components that are, FORTRAN-compatible.
 - B.1(13) says that a type is FORTRAN-compatible if it's declared in
   package INTERFACES.FORTRAN or it's defined to be FORTRAN-COMPATIBLE.
 - B.5(18) requires us to claim that the specified types (ie. all of them
   in INTERFACES.FORTRAN) are FORTRAN-compatible.

 - Ergo, if we provide INTERFACES.FORTRAN, then we must support
   convention FORTRAN for any type that is derived from, or has
   components of, any type within INTERFACES.FORTRAN.

 - But, if we don't provide INTERFACES.FORTRAN, then B.1(20) allows us to
   claim that we don't permit *any* FORTRAN-compatible type, and
   therefore, that there are *no* FORTRAN-eligible types in our
   implementation, and therefore, that B.5(20) is moot.

****************************************************************

From:   Brashear, Phil
Sent:   Friday, January 29, 1999 7:34 AM

On tests CXB5004 and CXB5005, an implementation rejects the Import pragma
because they do not define convention Fortran. As shown by CXB5001..3, they
do provide package Interface.Fortran, but they don't support actual linkages
to Fortran code.

The tests expect an implementation not fully supporting Fortran interfaces to
reject "with Interface.Fortran;"  In the past, we have had implementations do
that and have also had implementations that accept the entire program but fail
at link time (because no Fortran compiler is available).  Both behaviors have
been graded Not-Applicable.

We believe that rejecting the pragma (because of the undefined convention
Fortran) is a third way to handle this situation. Is this acceptable?


****************************************************************

From:   Brukardt, Randy
Sent:   Friday, January 29, 1999 1:33 PM

The discussion of AI-00204 at the Paris meeting suggests that such an
implementation is not allowed. However, it would be best if the AI
write-up made clear whether or not the package Interface.Fortran implies
support for convention Fortran, and vice versa. (Of course, any such
result should apply to all language conventions).

****************************************************************

From: 	Robert A Duff
Sent: 	Tuesday, February 02, 1999 9:58 AM

> Interface packages such as Interfaces.Fortran shall not be provided if
> the implementation does not support the interfacing pragma for that
> language. This applies also to other foreign languages including C and
> COBOL.

I think the ruling is silly.  It's perfectly harmless to have "extra"
Interfaces.* packages lying around.  And there's nothing in the RM
saying otherwise.  First, Implementation Advice ("should" rules) don't
count.  Second, the Impl Advice quoted in the AI, B.2(12) doesn't say
the same thing as the AI -- it says that if you support convention X,
you *should* have a package Interfaces.X.  Not the other way around.

Note that the AI claims to be a "confirmation", so it ought to follow
from the RM rules.  Preferably in an "obvious" way!  ;-)

Whether such "extra" packages are useful or not is irrelevant.  The ARG
is not in the business of forbidding useless things.  Such packages are
harmless, and the RM doesn't forbid them.  Therefore they're allowed.

The only reason this came up is because some ACVC tests have both a
"with Interfaces.Fortran" and also "pragma Convention(Fortran, ...)".
The grading criteria say that if the implementation complains about
the with-clause, that's OK, but if the implementation complains about
the pragma, that's not OK.

So we have a case of some test writer being slightly confused, and the
ARG then making that into law, by sheer invention of rules.

Some of our implementations currently violate this rule.  It would be
easy to fix -- we just have to delete the package Interfaces.Fortran.
Or, more likely, save it away somewhere for when we ever get around to
finishing the implementation of Fortran interfacing.  Therefore, from a
practical point of view, I don't much care which way this turns out.
The reason I'm saying something about it is that I don't like the idea
of test-driven language rulings (as opposed to RM-driven, or
user-needs-driven).

- Bob

****************************************************************

From: 	Robert Dewar
Sent: 	Tuesday, February 02, 1999 7:16 AM

<<Interface packages such as Interfaces.Fortran shall not be provided if
the implementation does not support the interfacing pragma for that
language. This applies also to other foreign languages including C and
COBOL.
>>

I find this completely wrong, it is extremely useful to have
Interfaces.COBOL around even if there is no COBOL compiler around.
As I read the AI, it is written up with exactly the contrary view.


<<However, whether Interfaces.Fortran is present or not, the provider of
the implementation must identify the Fortran compilers with which the
conventions agree and there must be at least one such compiler.
>>

It is that sentence that seems plain wrong, why does there have to be
at least one such compiler around.

I can't really speak for Fortran here, but for example, GNAT always
provides Interfaces.COBOL using standard IBM data formats shared by
many compilers.

This is useful on ALL machines, including those with no COBOL compiler,
since it allows an Ada program to read and process files generated by
an IBM-compatible COBOL compiler.

Perhaps I read the AI wrong, but certainly the summary and the above
quoted sentence seem to come to exactly the wrong conclusion here.

It is never helpful to force compilers to remove a useful feature for the
sake of some theoretical, and in this case plain silly, formal reason.

****************************************************************

From: 	Randy Brukardt
Sent: 	Tuesday, February 02, 1999 12:35 PM

Robert commenting on the AI:

<<Interface packages such as Interfaces.Fortran shall not be provided if
the implementation does not support the interfacing pragma for that
language. This applies also to other foreign languages including C and
COBOL.
>>

I find this completely wrong, it is extremely useful to have
Interfaces.COBOL around even if there is no COBOL compiler around.
As I read the AI, it is written up with exactly the contrary view.

Randy:

Supporting the Interfacing pragma does not require that a compiler exist.
Indeed, to properly support data representations, the convention name
COBOL, Fortran, etc. HAS to be supported.

If you know what compiler you are supporting, you can generate appropriate
import/export code. You don't need to actually have a compiler.

Back to Robert:

<<However, whether Interfaces.Fortran is present or not, the provider of
the implementation must identify the Fortran compilers with which the
conventions agree and there must be at least one such compiler.
>>

It is that sentence that seems plain wrong, why does there have to be
at least one such compiler around.

I can't really speak for Fortran here, but for example, GNAT always
provides Interfaces.COBOL using standard IBM data formats shared by
many compilers.

This is useful on ALL machines, including those with no COBOL compiler,
since it allows an Ada program to read and process files generated by
an IBM-compatible COBOL compiler.

Randy says:

I totally agree that no compiler should be allowed. I'm not so convinced
about the laissez-faire approach to handling this. It means that a user
cannot really depend on anything about interfacing (if X is supported,
that tells us nothing about whether anything else works), and it makes
interfacing untestable. (It would not be possible to fail the tests - they
would always be not applicable.)

In that case, I would rather withdraw the tests as of no value - the only
value they would have is to an implementor testing their compiler
in-house, and that is not the purpose of the ACATS.

Therefore, I think we HAVE to have some rules as to what support
is required if any support is.

							Randy.

****************************************************************

From: 	john barnes[SMTP:jgpb@JBINFO.DEMON.CO.UK]
Sent: 	Wednesday, February 03, 1999 3:13 AM

 Clearly this is going to have to be discussed again.

 I don't have very strong feelings about this topic. I wrote the AI as directed
 by the meeting and as written up in the minutes. But I thought it would
 prompt further discussion. Robert's point that the conventions might be well
defined by some other standard even if only de facto rather than having to refer
to an actual compiler is a very good one. It's no doubt better to have the
conventions defined by a standard than by some wretched compiler.

But I think it's untidy and confusing to provide an interfaces package without
supporting the convention pragma and that was certainly strongly felt at the
meeting if I recall correctly. However, everyone wasn't present.

 John

****************************************************************

From: 	Erhard Ploedereder
Sent: 	Wednesday, February 03, 1999 6:58 AM

>> Interface packages such as Interfaces.Fortran shall not be provided if
>> the implementation does not support the interfacing pragma for that
>> language. This applies also to other foreign languages including C and
>> COBOL.

Bob:
> I think the ruling is silly.  It's perfectly harmless to have "extra"
> Interfaces.* packages lying around.  And there's nothing in the RM
> saying otherwise.

Robert:
> I find this completely wrong, it is extremely useful to have
> Interfaces.COBOL around even if there is no COBOL compiler around.

I think it is neither silly nor wrong, just badly worded. It should not
say "interfacing pragma" but rather "convention pragma".

Look at the comment that prompted this whole issue. Do we consider it to be
conformant, if somebody types in the package spec, provides some dummy Ada
bodies that in effect convert Ada to Ada, and that's it ??

This is in gross violation of RM B.2(1), B.5(2) and RM B.5(20), combined with
1.1.3(17). Put simply: "You are not allowed to provide a package with
the same name as the predefined one that doesn't do what the RM prescribes, in
this case that the types have Fortran convention representation."

Erhard

****************************************************************

From: 	Robert Dewar[SMTP:dewar@GNAT.COM]
Sent: 	Wednesday, February 03, 1999 7:27 AM

<<I think it is neither silly nor wrong, just badly worded. It should not
say "interfacing pragma" but rather "convention pragma".
>>

Nope, that's wrong too.

Interfaces.COBOL is very useful even if you do not support pragma
Convention (COBOL, xxx).

Remember that Interfaces.COBOL is provided as part of the feature for
interfacing with COBOL, fine in this context of course you need the
pragmas.

But if you can't interface with COBOL, because there is no COBOL compiler,
then of course the RM does not force you to interface with COBOL!!!

However, you can still implement any or all of the relevant section to
provide useful facilities to a user, providing you implement them
correctly.

****************************************************************

From: 	Robert A Duff[SMTP:bobduff@WORLD.STD.COM]
Sent: 	Wednesday, February 03, 1999 10:02 AM

I really think the ARG has no business modifying the RM unless there's a
good reason.  There's no support in the RM for this imagined
restriction.  Therefore, to apply such a restriction, the ARG should
first argue that there's some concrete benefit to users, which I haven't
seen.  I've seen John saying it seems untidy, and Erhard being outraged
at implementor laziness, which may well be true -- bit it's pretty
marginal.

- Bob

****************************************************************

From: 	Erhard Ploedereder[SMTP:ploedere@INFORMATIK.UNI-STUTTGART.DE]
Sent: 	Wednesday, February 03, 1999 10:59 AM

Robert writes:
> Obvoiously the COBOL interfaces package is VERY useful even if you do not
> support the [convention] pragma.

Hmmm. Interfaces.COBOL might be a special case. Let me replay your argument
in my words to check whether I got it....
Because Interfaces.COBOL has all these Display_Format operations, it's
useful even if B.4(51) ("each type in Interfaces.COBOL is COBOL-compatible")
is violated. For really interfacing with COBOL at a binary level, you
obviously need the support of the various pragmas, but for writing text
files matching COBOL-expectations, the package alone is enough and pretty
useful.

Is that it ?

(I looked at Interfaces.C, too. And there similar benefits would be much more
marginal (Is_Nul_Terminated might be useful) and, in my opinion, even
detrimental if used as a packaged way of unsafe programming,
c.f., Interfaces.C.Strings.
For Interfaces.Fortran the benefits are non-existent, since it lacks any
useful interfaces.

****************************************************************

From: 	Robert Dewar
Sent: 	Wednesday, February 03, 1999 11:38 AM

Yes, and there is no issue of it violating "each type in Interfaces.COBOL
is COBOL-compatible". This is indeed true even if there is no pragma around
and no COBOL compiler around. It is not the case that the only way to make
things COBOL-comptible is using a pragma Convention. Who knows what
magic is in the private part of Interfaces.COBOL and in its body????

****************************************************************

From: 	Erhard Ploedereder[SMTP:ploedere@INFORMATIK.UNI-STUTTGART.DE]
Sent: 	Wednesday, February 03, 1999 11:21 AM

> I really think the ARG has no business modifying the RM unless there's a
> good reason.  There's no support in the RM for this imagined
> restriction.

Well, it's a confirmation AI. We're not modifying the RM.

And RM B.2(1), B.5(2), B.5(18) [and analogous sentences for the other language
packages], combined with 1.1.3(17), are repeated and ample justification to
call this a !confirmation. How you can read these paragraphs and come to
a different conclusion is beyond my understanding, but I'm listening :-)

So, if Bob's and Robert's opinion carries, the AI would need to be rewritten
to be a binding interpretation, nullifying the Annex B paragraphs cited
above by saying that these types shall be ..., IF pragma Convention is
supported. I sure hope that at least that's a universally agreed requirement
or else these Interface packages become a complete joke.

****************************************************************

From: 	Randy Brukardt
Sent: 	Wednesday, February 03, 1999 4:08 PM

>I am completely unable to read this restriction into the RM (and of course
>if it is there it is obviously wrong), but please restate your argument
>that this restriction is already there

B.3(61) says that an implementation SHALL support pragma convention for
a C-eligible type. (Each of the other sections have similar language). B.1(14-17)
makes it clear that such types can be constructed from the types in the package.
I don't see how you can get around the fact that the language ties the two
together.

Anyway, I see a larger problem here: there is absolutely nothing normative
in the manual that says that these packages are NOT required of all
implementations. The only thing that comes close is the Implementation
Advice in B.2(13), which says that implementions ought to support these
packages. But unless the section defining the package says that it is optional
(and these don't), they are a required part of the standard.  (Remember, B
is not a Specialized Needs Annex!!!). The Implementation Advice proves
intent, but that's all it can do (especially because it never says that you
don't have to implement these packages).

So, now I'm certain that this needs to be a Binding Interpretation (at least to
get to the Dewar/Duff position). Unless of course we solve Robert's
complaint by requiring Interfaces.COBOL of all implementations...


                                        Randy.

****************************************************************

From: 	Jean-Pierre Rosen
Sent: 	Wednesday, February 03, 1999 12:46 PM

Robert says:
>Interfaces.COBOL is very useful even if you do not support pragma
>Convention (COBOL, xxx).
>
>Remember that Interfaces.COBOL is provided as part of the feature for
>interfacing with COBOL, fine in this context of course you need the
>pragmas.
>
>But if you can't interface with COBOL, because there is no COBOL
>compiler, then of course the RM does not force you to interface with
>COBOL!!!

But, as you said, the goal is to be able to interface with Cobol data.
This does not require a COBOL compiler, but it would be logical to be
able to have a pragma Convention COBOL for data types - at least.

Of course, you can argue that you can use only COBOL data types
defined in package Interfaces.COBOL, not user defined ones. It just
doesn't seem consistent to me.

****************************************************************

From: 	Robert Dewar
Sent: 	Thursday, February 04, 1999 6:42 AM

<<But, as you said, the goal is to be able to interface with Cobol data.
This does not require a COBOL compiler, but it would be logical to be
able to have a pragma Convention COBOL for data types - at least.

Of course, you can argue that you can use only COBOL data types
defined in package Interfaces.COBOL, not user defined ones. It just
doesn't seem consistent to me.
>>

Fully implementing pragma convention COBOL is a much bigger job than just
implementing Interfaces.COBOL.

Interfaces.COBOL is useful even if you don't have pragma Convention COBOL.

So why do you want to tell a user: "sorry, I know you would find it useful
to have Interfaces.COBOL, and I would be happy to provide it to you, but the
ARG says I can't do that unless I also provide pragma Convention COBOL, so
you can't have it. Yes, I know you don't need pragma Convention COBOL, but
that's the way the rule is. Yes, I know it makes no sense, don't ask me,
complain to the ARG.

Being able to deal with primitive COBOL data elements is definitely useful
on its own, without the full mechanism of, e.g. copying the effect of
alignment on COBOL records (indeed we provide no built in mechanism anyway
for dealing with SYNCHRONIZED, so a useful implementation of pragma
Convention COBOL would have to include an extra pragma to handle
SYNCHRONIZED in any case, and for sure the RM does not require that.

So really what you are threatening to say is

You may not provide the useful facility Interfaces.COBOL unless you also
provide a partial implementation of pragma Convention COBOL that is unlikely
to be of use.

This makes no sense. I am amazed that we even spend time discussing the
possibility of such an obviously stupid restriction.

It is certainly nice if all compilers provide all features (right now in
the real world, I think only GNAT provides Interfaces.COBOL in any case,
and it fully implements interfacing to COBOL [on appropriate machines we
pass the test of actually calling COBOL].

The approach being suggested here means that GNAT would have to remove
Interfaces.COBOL on some machines if we really insisted in actual interfacing,
well thankfully that silly idea seems to be gone, and GNAT does always allow
pragma Convention COBOL.

But what about other compilers? I think it would be useful to encourage
people to provide Interfaces.COBOL even if they don't provide other useful
stuff. In fact I think other compilers could even adopt the GNAT
implementation, I don't think it relies on non-standard features (Aonix
did this for a while for some of the math routines, given the GPL status
it is quite legitimate to do this).

Why on EARTH would we tell other vendors that they cannot provide this
useful facility. It boggles the mind for the ARG to be in the business
of issuing rules that are detrimental to implementors and users alike!

****************************************************************

From: 	Randy Brukardt
Sent: 	Thursday, February 04, 1999 10:21 AM

>Interfaces.COBOL is useful even if you don't have pragma Convention COBOL.

If we're going to allow compilers to support features of dubious utility, then there is
no advantage to these packages being optional. We should just follow the wording
(not the intent) of the RM, and require them of everyone. Implementing simple
versions of these packages is just about trivial, if you make no requirement about
the types being compatible with a particular compiler. (Which is what Robert is
saying he wants - because that is what the effect of not requiring a pragma
Convention.)

                                                        Randy.

****************************************************************

From: 	Tucker Taft
Sent: 	Thursday, February 04, 1999 5:16 PM

Randy Brukardt wrote:
>
> >I am completely unable to read this restriction into the RM (and of course
> >if it is there it is obviously wrong), but please restate your argument
> >that this restriction is already there
>
> B.3(61) says that an implementation SHALL support pragma convention for
> a C-eligible type. (Each of the other sections have similar language). B.1(14-17)
> makes it clear that such types can be constructed from the types in the package.
> I don't see how you can get around the fact that the language ties the two
> together.

Well, I sort of hate to wade into this morass.  However,
what B.3(61) says, in my view, is that to support *interfacing
to C*, the implementation must support convention C.  B.3(1),
similarly, indicates that to support *interfacing to C*,
the implementation must provide the package Interfaces.C and
its children.  Nowhere does it say that if the implementation
does *not* fully support interfacing to C, then it must *not*
provide Interfaces.C, nor for that matter must it *not* support
pragma Convention C.

For the Specialized Needs annexes, we clearly allow subset
implementations, so long as the implementation does not claim
to fully support the annex.

I believe we have adopted this same attitude relative to Annex B
(even though it is not officially a Special Needs Annex), that
implementations need not fully support interfacing to all languages.
Nowhere do I see a requirement for an all or nothing support of
interfacing to a particular language.

> ...
> So, now I'm certain that this needs to be a Binding Interpretation (at least to
> get to the Dewar/Duff position). Unless of course we solve Robert's
> complaint by requiring Interfaces.COBOL of all implementations...
>

I agree we should make it clear that support for particular "foreign"
languages is optional, and that the support may be partial support
or full support.

Full support requires supporting both the corresponding Interfaces.*
package(s) and the corresponding convention.  Partial support
is any well-defined subset of that, using the guidelines of 1.1.3(17)
for indicating what is a "well-defined subset."  E.g., the unsupported
capability shall be identified before run-time, or by an exception
at run-time.  There is no all-or-nothing requirement.

****************************************************************

From: 	john barnes
Sent: 	Friday, February 05, 1999 2:05 AM

In message stt@AVERSTAR.COM writes:
>
> Well, I sort of hate to wade into this morass.  However,
> what B.3(61) says, in my view, is that to support *interfacing
> to C*, the implementation must support convention C.  B.3(1),
> similarly, indicates that to support *interfacing to C*,
> the implementation must provide the package Interfaces.C and
> its children.  Nowhere does it say that if the implementation
> does *not* fully support interfacing to C, then it must *not*
> provide Interfaces.C, nor for that matter must it *not* support
> pragma Convention C.

So the "should" in B.2(12) is overridden by an implicit "shall" in
B.3(1).

As a result (as writtne) the "should" only applies to languages other
than C, COBOL and Fortran so those three languages are special. Not
quite what I would have expected. I would have expected Ada to treat
all languages the same except that it tells you what to do if you
want to support C, COBOL and Fortran but leaves you on your own
for others.

****************************************************************

From: 	Erhard Ploedereder
Sent: 	Friday, February 05, 1999 12:13 PM

Erhard:
<<So, if Bob's and Robert's opinion carries, the AI would need to be rewritten
to be a binding interpretation, nullifying the Annex B paragraphs cited
above by saying that these types shall be ..., IF pragma Convention is
supported. I sure hope that at least that's a universally agreed requirement
or else these Interface packages become a complete joke.
>>

Robert:
> Sorry, I don't get the joke, what are you talking about here???

I am talking about the view that any user of the packages will have: he
will expect that the effects of a pragma Convention, whatever
they may be on binary infacing of data, apply to the types in these
packages. I.e., Interfaces.C.long_double really,really is of the same
representation as in C.

Note that in the position that you're pushing, Interfaces.C is perfectly
conforming to the Standard if it defines
    type long_double is digits 6;  -- too busy to worry about it now

I am struggling with the question of what to tell the user, when he asks:
What must be the case, so that I can assume Interfaces.C.long_double is
binary compatible with the long_double in my C program ?

The AI in its current form would say (and so does the RM today): This is the
case, if the package exists. No major buts and ifs. (Maybe a few minor buts
and ifs, well documented.:-)

My original response quoted at the beginning of this message tried a
compromise: Yes, there is a "if", namely support for pragma Convention.

I am certainly unhappy about the answer: "Oh, you thought this type
declaration in the Interface package means something other than a name ?
Sorry, it really is just a name and an implementation need not guarantee
anything about the type."

****************************************************************

From: 	Robert A Duff
Sent: 	Friday, February 05, 1999 1:19 PM

> Note that in the position that you're pushing, Interfaces.C is perfectly
> conforming to the Standard if it defines
>     type long_double is digits 6;  -- too busy to worry about it now

No, that would not be conforming.  I admit that the ACVC would not catch
it, but that's a separate issue.  I don't see how the AI negates this
requirement.

Note that support for pragma Convention is not the same thing as the
conventions of things in these packages.  We always assumed that
Interfaces.C.long_double would get it's convention "by magic" in many
(most?)  implementations -- not via pragma Convention.

- Bob

****************************************************************

From: 	Robert I. Eachus
Sent: 	Friday, February 05, 1999 1:17 PM

>                                                 However,
> what B.3(61) says, in my view, is that to support *interfacing
> to C*, the implementation must support convention C.  B.3(1),
> similarly, indicates that to support *interfacing to C*,
> the implementation must provide the package Interfaces.C and
> its children.  Nowhere does it say that if the implementation
> does *not* fully support interfacing to C, then it must *not*
> provide Interfaces.C, nor for that matter must it *not* support
> pragma Convention C.

   And I agree with this as well.  In 1.1.3(16) we read (all emphasis mine):

"An implementation that conforms to this Standard shall support each
capability required by the core language as specified."

   In B.2(11) I see:

     Implementation Permissions

"An implementation MAY provide implementation-defined library units that
are children of Interfaces, and may add declarations to the visible part of
Interfaces in addition to the ones defined above."

   Later B.2(13):

     Implementation Advice

"An implemenation supporting an interface to C, COBOL, or Fortran SHOULD
provide the corresponding packages described in the following clauses."

   And back to Chaper 1.1.3(17):

"An implementation conforming to this International Standard MAY provide
additional attributes, LIBRARY UNITS, and pragmas.  However, it shall not
provide any attribute, library unit, or pragma having the same name as an
attribute, library unit or pragma(respectively) specified in a Specialized
Needs Annex unless the provided construct is either as specified in the
Specialized Needs Annex or is more limited in capability than that required
by the Annex."

   So there seems to be NO way to reject an implementation that provides a
package Interfaces.Cobol or Interfaces.C no matter what is in the package.
IF Annex B was a Specialized Needs Annex, there would still be no
justification for rejecting a child of Interfaces that conforms to the
Standard.  We might want to extend 1.1.3 to include that requirement, but
it is not there now. But it is real hard to argue that may in B.2(11) away.

****************************************************************

From: 	john barnes
Sent: 	Saturday, February 06, 1999 2:00 AM

> At 08:05 AM 2/5/99 GMT, john barnes wrote:
>
> >So the "should" in B.2(12) is overridden by an implicit "shall" in
> >B.3(1).

I was stating what I thought Tuck said B.3(1) meant. Not that I personally
necessarily believed it.

I could interpret B.3(1) as stating these things (packages and pragmas) are
the domain of discourse but not imposing any requirements.

>
>    That is a real stretch that ignores the one paragraph between them,
> B.2(13) quoted above.  I don't see any reason for reading a 'shall' into
> B.3(1), when it is preceded by an unambigous 'should'.
>

Yes that's two shoulds versus one suspected shall.

I agree.


However, maybe we should concentrate on what we want and then decide how the
RM should be fixed if it doesn't provide it.

****************************************************************

From: 	Tucker Taft
Sent: 	Saturday, February 06, 1999 7:31 AM

> > At 08:05 AM 2/5/99 GMT, john barnes wrote:
> >
> > >So the "should" in B.2(12) is overridden by an implicit "shall" in
> > >B.3(1).
>
> I was stating what I thought Tuck said B.3(1) meant. Not that I personally
> necessarily believed it.

Then I was unclear (I suspect you didn't notice one of my "not"s in
the message -- I got carried away with double negatives).

What I was *trying* to suggest was that support for foreign
languages is effectively optional.  Furthermore, there is no "all or nothing"
requirement for supporting a particular language.  You may provide
the Interfaces.X package, or the pragma for convention X, or neither,
or both.  However, to claim to "fully support interfacing to X" you
must supply both.

Some have argued (I think) that providing Interfaces.X without
supporting pragma convention X is not useful, or is misleading.
I don't agree, but in any case, I don't see any justification
for requiring an all-or-nothing rule here, while we don't require
an all-or-nothing rule in the Specialized Needs Annexes.

> ...
> Yes that's two shoulds versus one suspected shall.
>
> I agree.
>
>
> However, maybe we should concentrate on what we want and then decide how the
> RM should be fixed if it doesn't provide it.

I think we should make it more clear that support for foreign languages
is optional, and that partial support is allowed.  Whether this
is a binding interpretation or a ramification or a confirmation seems
relatively minor in my view.  I will happily sign up for whatever
categorization the majority believes is most appropriate.

****************************************************************

From: 	Jean-Pierre Rosen
Sent: 	Saturday, September 25, 1999 4:21 AM

> !corrigendum
>
> Replace the first sentence of B.2(12) which states
>
> "For each implementation-defined convention identifier, there should be
> a child package of package Interfaces with the corresponding name."
>
> by
>
> "A child package of package Interfaces with the name of a convention may
> be provided irrespective of whether the convention is supported by the
> pragma Convention."
>
>
I think "replace" should be "add after".
What the old paragraph says, is that if you support a convention, you'd
better provide the corresponding package, which makes sense to me: if you
interface with programs, you'd better interface with data also (note that
there is a "should").

OTOH, what the second paragraph says is that you can provide the package
even if you don't support the convention. I'm OK with that, but I don't
think it subsumes the first paragraph.

****************************************************************

From: 	John Barnes
Sent: 	Saturday, October  2, 1999 7:26 AM

The original view of the ARG was that you can provide the convention pragma
with or without the package (the paragraph says should not shall) but not the
package without the pragma.

But the meeting in Burlington changed its mind to say let either be provided
independently. Hence I rewrote it that way.

****************************************************************


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