From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 X-Received: by 10.182.246.225 with SMTP id xz1mr1413159obc.14.1381946085862; Wed, 16 Oct 2013 10:54:45 -0700 (PDT) X-Received: by 10.49.75.168 with SMTP id d8mr129852qew.3.1381946085809; Wed, 16 Oct 2013 10:54:45 -0700 (PDT) Path: border1.nntp.dca3.giganews.com!backlog4.nntp.dca3.giganews.com!border4.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!usenet.blueworldhosting.com!feeder01.blueworldhosting.com!npeer02.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!o2no8459504qas.0!news-out.google.com!9ni45434qaf.0!nntp.google.com!i2no16006993qav.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Wed, 16 Oct 2013 10:54:45 -0700 (PDT) In-Reply-To: <54aa8ad2-cd98-4f3e-bef9-494ddaefe4e9@googlegroups.com> Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=82.43.197.131; posting-account=g4n69woAAACHKbpceNrvOhHWViIbdQ9G NNTP-Posting-Host: 82.43.197.131 References: <1374ac32-0fb5-4589-a9a5-7740030fd3c6@googlegroups.com> <4bb47482-ccb9-4641-a702-2b2978100ff9@googlegroups.com> <5b59543c-7c48-4427-afc6-30289f6d8895@googlegroups.com> <54aa8ad2-cd98-4f3e-bef9-494ddaefe4e9@googlegroups.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <50cd020a-480f-4569-990b-b2861f628bc1@googlegroups.com> Subject: Re: Passing a String to a C/C++ Subprogram (Special Case) From: Martin Injection-Date: Wed, 16 Oct 2013 17:54:45 +0000 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Received-Bytes: 6331 X-Original-Bytes: 6541 Xref: number.nntp.dca.giganews.com comp.lang.ada:183636 Date: 2013-10-16T10:54:45-07:00 List-Id: On Wednesday, October 16, 2013 6:42:29 PM UTC+1, Eryndlia Mavourneen wrote: > On Wednesday, October 16, 2013 12:32:36 PM UTC-5, Martin wrote: >=20 > > On Tuesday, October 15, 2013 10:02:17 PM UTC+1, Eryndlia Mavourneen wro= te: >=20 > >=20 >=20 > > > On Tuesday, October 15, 2013 3:11:30 PM UTC-5, Adam Beneschan wrote: >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > On Tuesday, October 15, 2013 12:54:18 PM UTC-7, Eryndlia Mavourneen= wrote: >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > I have a couple of strings that are bounded; that is, they are es= sentially fixed-length strings, and I need to pass them as "in" parameters = to a subprogram that may or may not be written in C/C++. I don't really wa= nt to hassle with the Interfaces packages for this, since the subprogram la= nguage is indefinite, and the strings are part of a package that many other= s likely will want to use, and the strings most likely will be used as stan= dard Ada fixed-length strings. >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > Q: Is there any reason that I cannot just declare each of them in= this way, assuming the subprogram is written in C/C++: >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > . . . >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > A_String : String (1 .. 30); >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > pragma Convention (C, A_String); >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > . . . >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > procedure C_Prog (C_String : in String); >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > pragma Import (Entity =3D> C_Prog, ...); >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > begin >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > C_Prog (C_String =3D> A_String); >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > . . . >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > > and have it work properly? >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > B.3(70) says, "An Ada parameter of an array type with component typ= e T, of any mode, is passed as a t* argument to a C function, where t is th= e C type corresponding to the Ada type T." Since a String is defined as an= array of Character in Ada, this should cause a "char*" argument to be pass= ed. However, this is in a section marked "Implementation Advice", so there= 's a possibility that a particular Ada compiler may not conform. You'll wa= nt to check the Ada compiler manual and/or try it yourself and see what cod= e it generates. Note that this means the 'First and 'Last of the string pa= rameter won't be passed to the C routine. But it looks like you know that = already.=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > > -- Adam >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > Yes, Adam. Thank you. Of course, Annex B is optional anyway. lol >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > I guess you choose your poison. >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > >=20 >=20 > >=20 >=20 > > > -- Eryndlia Mavourneen (KK1T) >=20 > >=20 >=20 > >=20 >=20 > >=20 >=20 > >=20 >=20 > >=20 >=20 > > Annex B is part of the 'core language' - it isn't optional. Annex A and= J are also 'core'. The 'Special Needs Annex' sections are the 'optional' p= arts of the language. See 1.1.2 and 1.1.3. >=20 > >=20 >=20 > >=20 >=20 > >=20 >=20 > > -- Martin >=20 >=20 >=20 > In the Ada95 LRM (I have to use Ada95.), in the introduction to Annex B (= B 2/3) it states: "Support for interfacing to any foreign language is opti= onal." >=20 >=20 >=20 > -- Eryndlia Mavourneen (KK1T) That looks like Ada2012 RM rather than Ada95 (or Ada2005) [http://www.ada-a= uth.org/standards/12rm/html/RM-B.html]. But I do like the Ada2012 wording...it seems clearer - either the compiler = has to indicate the lack of support; or exception has to be raised. If neit= her of those occur then your code should work as expected. -- Martin