From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on ip-172-31-65-14.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-3.2 required=3.0 tests=BAYES_00,NICE_REPLY_A, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "Jeffrey R.Carter" Newsgroups: comp.lang.ada Subject: Re: GNAT or Language Problems? Date: Thu, 22 Jun 2023 14:56:42 +0200 Organization: A noiseless patient Spider Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Thu, 22 Jun 2023 12:56:42 -0000 (UTC) Injection-Info: dont-email.me; posting-host="9b320abd6a04c902207fcf7efd7448a0"; logging-data="3422879"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+x/ZCyTf4VtrCMaNLCaFqRkBEdKGCeS84=" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Cancel-Lock: sha1:5A8iuxaidDPJLQsvKWncTjAWsSg= In-Reply-To: Content-Language: en-US Xref: news.eternal-september.org comp.lang.ada:65340 List-Id: On 2023-06-22 11:51, Randy Brukardt wrote: > You missed my point: The requirement that the subtypes are statically > compatible was newly added. That applies to *all* subtypes, not just those > with predicates. The reason the requirement was added had to do with > predicates, but it might affect some marginal cases beyond that. It's a > weaker requirement than static matching, but stronger than no requirement at > all. > > As I said the other day, you need to check if 4.9.1 allows or disallows your > example (that's where the definition of static compatibility is found). If > it allows it, then it's a compiler bug, if it doesn't allow it, it's an > incompatibility with a language fix and you need to find a different way to > do whatever it is you are doing. Sorry, but I think you're wrong. The problem isn't static compatibility; it's static matching. The error msg says the subtypes must statically match, and the wording in 7.4(6/3) for deferred constants (which this is) refers to statically matching constraints. So static compatibility doesn't seem to be the issue. > I don't have the energy tonight to go > through that exercise myself (I apparently brought back a bug from Lisbon, > and have spent much of the last several days in bed - but for some reason I > seem to only be able to sleep during the day. Really louses up life...). Sorry to hear that. Hope you feel better soon. > "Jeffrey R.Carter" wrote in message > news:u6jtue$16d9e$1@dont-email.me... >> On 2023-06-17 09:28, Randy Brukardt wrote: >>> Regarding your second problem, refer to AI22-0041-1. >>> >>> Essentially, there are problems if predicates are involved. We changed >>> the >>> rule to require static compatibility (as a Binding Interpretation). I >>> don't >>> have the energy to look up what "static compatibility" requires in this >>> case >>> (enjoy figuring out 4.9.1). In some cases, it requires static matching, >>> in >>> others, it has weaker requirements. >> >> There are no predicates involved. One can cut it down to just the type and >> constant: >> >> package B_Strings_Prob is >> type B_String (Max_Length : Positive := 1_000) is tagged limited >> private; >> >> Null_B_String : constant B_String; -- A string of zero characters >> private -- B_Strings_Prob >> type B_String (Max_Length : Positive := 1_000) is tagged limited record >> Len : Natural := 0; >> Value : String (1 .. Max_Length) := (1 .. Max_Length => ' '); >> end record; >> >> Null_B_String : constant B_String := (Max_Length => 1, others => <>); >> end B_Strings_Prob; >> >> and still get the error: >> >> $ gnatmake -gnatc b_strings_prob.ads >> x86_64-linux-gnu-gcc-13 -c -gnatc b_strings_prob.ads >> b_strings_prob.ads:12:04: error: subtype does not statically match >> deferred declaration at line 5 >> gnatmake: "b_strings_prob.ads" compilation error >> >> I don't see any mention of AI22-0041-1 in ARM 7.4. >> >>> I don't have the time or energy tonight to look into your other problem. >>> (I'm waiting for a backup to finish, or I would have already gone home -- >>> since I only got back from Lisbon last night, I'm not equipped for my >>> usual >>> late night work...) >> >> I'm surprised you're this functional already. >> >> -- >> Jeff Carter >> "I was in love with a beautiful blonde once, dear. >> She drove me to drink. That's the one thing I'm >> indebted to her for." >> Never Give a Sucker an Even Break >> 109 >> > > -- Jeff Carter "[I]t is easy to use [Ada] just like any other language: using only predefined types, using packages just for separate compilation (without any consideration for information hiding), ignoring generics altogether, etc. I have seen projects doing this; they didn't get much gain from using Ada, and spent a lot of time fighting the compiler." Jean-Pierre Rosen 165