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=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,d71460587da14d5b X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-07-30 22:35:58 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!headwall.stanford.edu!newshub.sdsu.edu!elnk-nf2-pas!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!newsread4.news.pas.earthlink.net.POSTED!not-for-mail From: "Matthew Heaney" Newsgroups: comp.lang.ada References: Subject: Re: Importing C structs? X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: <1V1Wa.299$jp.55@newsread4.news.pas.earthlink.net> Date: Thu, 31 Jul 2003 05:35:57 GMT NNTP-Posting-Host: 65.110.133.134 X-Complaints-To: abuse@earthlink.net X-Trace: newsread4.news.pas.earthlink.net 1059629757 65.110.133.134 (Wed, 30 Jul 2003 22:35:57 PDT) NNTP-Posting-Date: Wed, 30 Jul 2003 22:35:57 PDT Organization: EarthLink Inc. -- http://www.EarthLink.net Xref: archiver1.google.com comp.lang.ada:41056 Date: 2003-07-31T05:35:57+00:00 List-Id: "Ching Bon Lam" wrote in message news:Xns93C9C9EB630Fcblamstudentutwenten@194.109.133.20... > > that would be: > > type DB is interfaces.c.extensions.opaque_structure_def; This is probably overkill. For an opaque type all you need to do is: type DB_Type is limited null record; type DB_Access is access all DB_Type; for DB_Access'Storage_Size use 0; pragma Convention (C, DB_Access); > -- i have too less information about DBTYPE, so i assume > -- it's just a struct > type DBTYPE is interfaces.c.extensions.opaque_structure_def; > > function dbopen > (file : interfaces.c.char_array; > flags : interfaces.c.int; > mode : interfaces.c.int; > type : DBTYPE; > openinfo : interfaces.c.extensions.void_ptr) > return DB; > > pragma Import(C, dbopen, "dbopen'); The type of parameter file is incorrect. The char_array type is an unconstrained Ada array type, which does not correspond directly to any C type. Specifically, your problem is that on the Ada side a dope vector describing the array object is passed -- this is definitely *not* what you want. You need to use the type Interfaces.C.Strings.chars_ptr instead. You can probably use System.Address for void*. The C type void* was accidently omitted from Interfaces.C in the Ada95 standard, but I assume that oversite will be corrected in a future version of the language. It's not clear whether your return type should be DB or an explicit access type (as in DB_Access), because I'm not familiar with the package Interfaces.C.extensions. I would use DB_Access, which is completely portable. The type DBTYPE is a bit of a mystery at this point, since structs aren't typically passed by value in C. Perhaps DBTYPE is really a pointer?