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 2002:a6b:1b85:: with SMTP id b127-v6mr556217iob.51.1535313250374; Sun, 26 Aug 2018 12:54:10 -0700 (PDT) X-Received: by 2002:aca:2b06:: with SMTP id i6-v6mr217752oik.0.1535313250254; Sun, 26 Aug 2018 12:54:10 -0700 (PDT) Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!news.linkpendium.com!news.linkpendium.com!news.snarked.org!border2.nntp.dca1.giganews.com!nntp.giganews.com!w19-v6no2800998itb.0!news-out.google.com!c63-v6ni3111ith.0!nntp.google.com!g24-v6no2795162iti.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Sun, 26 Aug 2018 12:54:09 -0700 (PDT) In-Reply-To: <2145221813.556924687.162377.laguest-archeia.com@nntp.aioe.org> Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=47.185.195.62; posting-account=zwxLlwoAAAChLBU7oraRzNDnqQYkYbpo NNTP-Posting-Host: 47.185.195.62 References: <309225242.556906218.575482.laguest-archeia.com@nntp.aioe.org> <2145221813.556924687.162377.laguest-archeia.com@nntp.aioe.org> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <3892c779-2924-405c-b88d-19389fc5ba3e@googlegroups.com> Subject: Re: Studying and Maintaining GNAT, Is There Any Interest in a New Group? From: "Dan'l Miller" Injection-Date: Sun, 26 Aug 2018 19:54:10 +0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Xref: reader02.eternal-september.org comp.lang.ada:54261 Date: 2018-08-26T12:54:09-07:00 List-Id: On Saturday, August 25, 2018 at 4:48:07 PM UTC-5, Luke A. Guest wrote: > wrote: >=20 > > However I am discouraged with what you are saying about the bugs being = on > > the compiler side and not so much in the RTS. >=20 > It=E2=80=99s more the bugs are in the Ada front end, not the GCC backend,= which is > the codegen. Although it might be quibbling over the definition of =E2=80=9Cfront-end=E2= =80=9D and =E2=80=9Cback-end=E2=80=9D, it is my belief that the vast majori= ty of the bugs outside of the runtime is either: 1) front-end proper: lack of fidelity (to the _LRM_ or to nuanced explanations in the _AARM_) in= the Ada-language semantic-adornment of the AST and 2) lack of fidelity in the GIGI tree-transducer middle layer (which might b= e truly one-of-a-kind unique to GNAT) effectively =E2=80=A2outside=E2=80=A2= the Ada-language-source-code front-end proper and the GENERIC/GIMPLE/RTL b= ack-end proper: Between a) the Ada-language semantic-tree in the written-in-Ada front-end p= roper and b) the GCC GENERIC/GIMPLE/RTL back-end that is shared among all G= CC languages, there exists the GIGI () tree-transducer that observes snippe= ts of Ada-front-end's semantically-adorned AST to then instantiate the anal= ogous C/C++-language semantics in that branch of the GENERIC/GIMPLE's back-= end semantic tree. There are 2 areas where GNAT can easily make a mistake: 1) misinterpret (or malenforce) the normative _LRM_ and/or the nuanced expl= anations in the _AARM_ in the Ada semantically-adorned AST written in Ada l= anguage or 2) mistranscribe the =E2=80=98equivalent=E2=80=98 C/C++ semantics in GENERI= C/GIMPLE via the GIGI tree transducer, written in C language. Just like be= auty, =E2=80=98equivalent=E2=80=99 degenerates to: equivalent is in the ey= e of the beholder. (And the human being of high IQ has a bigger eye-of-the= -beholder than GIGI's observation of mere subset of the Ada AST. GIGI's ey= e-of-the-beholder naturally has tunnel vision.) On Saturday, August 25, 2018 at 5:05:52 PM UTC-5, Luke A. Guest wrote: > A new compiler needs a radical new design. Luke, GIGI is the general vicinity for fulfilling your prophetic prediction= of the future: A radical new Ada-compiler design would eliminate the tree= -transducer's transcription of snippets of Ada's semantically-adorned AST (= in Ada-language source code) into GENERIC/GIMPLE C/C++ semantic tree (in C-= language source code). In short, a radical new Ada-compiler design would e= liminate GIGI. Luke & Shark8 take especial note: eliminate the need for G= IGI entirely, then one has a drastically entirely-different-than-GNAT desig= n for a next-gen Ada compiler. Luke, despite your ridicule of studying Ada= 's antiquity, =E2=80=A2that=E2=80=A2 elimination of GIGI is precisely why s= tudying William Wulf's DIANA from decades ago is intellectually stimulating= & rewarding as getting the creative juices flowing in the mind when contem= plating what a next-gen Ada compiler might have at its heart instead of the= bug-prone complication that GNAT has at its heart: AdaAST-GIGI-C/C++AST, = 2 separate trees and a transducer-of-clever-snippets between them. (I susp= ect sometimes the scope of that cleverness there in GIGI is insufficiently = narrow/not-omniscient-enough, hence mistranscription bug.) Although Figure 1.1 is the front-end/back-end diagram that most people hold= in their head (and dear to their heart) from a compiler-construction textb= ook, I find Figure 1.2 to much more lucidly reveal GNAT's inner workings in= a nutshell for repeated reference in the mind's eye: https://www2.adacore.com/gap-static/GNAT_Book/html/node5.htm#SECTION0312000= 0000000000000 It is not entirely clear (to me) what GIGI stands for, btw. One of the =E2= =80=9CG=E2=80=9Ds could stand for GNAT; the other could stand for GENERIC o= r GIMPLE. One of the =E2=80=9CI=E2=80=9Ds could stand for instantiation (a= s in instantiating a snippet/extract of the Ada AST into GENERIC/GIMPLE's C= -language tree). One guess: GNAT-Internal GENERIC/GIMPLE Instatiator. Pe= rhaps only the original designers of GIGI know for sure: Robert Dewar, RWS= , perhaps Edmond Schonberg.