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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,b307bd75c8071241 X-Google-Attributes: gid103376,public From: "John G. Volan" Subject: Re: Assuaging sour grapes :-) [was: newbie Q: storage management] Date: 1997/05/07 Message-ID: <3370B12E.499D@sprintmail.com>#1/1 X-Deja-AN: 240007301 References: <5k5hif$7r5@bcrkh13.bnr.ca> <336A065B.41C6@magellan.bgm.link.com> <336E15A4.167E@magellan.bgm.link.com> <5knhge$mul@top.mitre.org> <336FDF8B.73AF@sprintmail.com> <52F0EC12E20AA44E.5796B5986C85CB4B.8C3BF60EE8ED6C1C@library-proxy.airnews.net> <33708E99.2186@sprintmail.com> Reply-To: johnvolan@sprintmail.com Newsgroups: comp.lang.ada Date: 1997-05-07T00:00:00+00:00 List-Id: Sorry, I need to make a few clarifications: John G. Volan wrote: > > Kevin Cline wrote: > > > > On most systems, dynamically loaded libraries can be built from C or > > C++ code. The library source code is portable, although the commands to build > > the library from source vary from system to system. > > How is Ada95 different here? Isn't it possible to create DLL's from > Ada95 source code, too? (For instance, using Aonix ObjectAda?) And even > if current implementations of Ada95 don't happen to generate DLLs, isn't > it at least feasible in principle? I should have said: "Isn't it feasible in principle using the _current_ definition of Ada95, without need for a language change?" ObjectAda for instance supports pragmas Import and Export with Convention=>DLL, couldn't other compilers just do the same? I see the portability issue: Without a standard definition of "dynamic linkage", different implementors could come up with different solutions; the best we could hope for is for informal agreement between vendors to support a de-facto standard. Then there's portability across platforms: Isn't dynamic linkage an operating-system dependent thing? Can you take a DLL written in C or C++ on WindowsNT and port it, and the applications that use it, immediately to any Unix box? If so, that's interesting, what would hinder us from doing the same with Ada95? On the other hand, if dynamic linkage mechanisms are OS-specific, how can we possibly invent something at the language-level that magically gives us portability? Maybe it's already been done: Consider Java, and Ada95=>JVM compilers like ObjectAda or AppletMagic. A JVM program isn't "linked" per se; class files get loaded as they are needed. However, I don't know whether a given JVM execution can re-load a different class file to replace an already-loaded class. > My question remains: What would "arrays of packages as first- or second- > class objects" give you? It seems to me that there's nothing in C or > C++ that makes it easier to dynamically load different versions of the > same package/class. It's still an extra-linguistic mechanism: It > requires configuration management mechanisms outside the programming > language level. > > Or am I still missing something...? ------------------------------------------------------------------------ Internet.Usenet.Put_Signature (Name => "John G. Volan", Home_Email => "johnvolan@sprintmail.com", Slogan => "Ada95: The World's *FIRST* International-Standard OOPL", Disclaimer => "These opinions were never defined, so using them " & "would be erroneous...or is that just nondeterministic now? :-) "); ------------------------------------------------------------------------