220 40322 article Path: news.gmane.org!.POSTED!not-for-mail From: Daniel Gutson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Runtime code generation and self modifying code Date: Fri, 5 Oct 2018 00:45:40 -0300 Lines: 138 Approved: news@gmane.org Message-ID: References: <4489f889-977c-45f2-8a2f-186ee3b06bff@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="000000000000ae03de0577731b2e" X-Trace: blaine.gmane.org 1538711033 15783 195.159.176.226 (5 Oct 2018 03:43:53 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 5 Oct 2018 03:43:53 +0000 (UTC) To: std-proposals Original-X-From: std-proposals+bncBDE3NBMV6UFBB4V43POQKGQEGUB33QA@isocpp.org Fri Oct 05 05:43:49 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lj1-f199.google.com ([209.85.208.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g8H1p-0003um-MM for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id h10-v6sor2416819lfm.53.2018.10.04.20.45.53 for (Google Transport Security); Thu, 04 Oct 2018 20:45:53 -0700 (PDT) Received-SPF: pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a19:54c1:: with SMTP id b62-v6mr5378191lfl.14.1538711152885; Thu, 04 Oct 2018 20:45:52 -0700 (PDT) In-Reply-To: <4489f889-977c-45f2-8a2f-186ee3b06bff@isocpp.org> X-Original-Sender: danielgutson@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=ck3mpdou; spf=pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=danielgutson@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:40322 Archived-At: --000000000000ae03de0577731b2e Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable No, just please don't. SMC has tons of consequences, from security perspective (check https://en.wikipedia.org/wiki/W%5EX and also triggering antivirus heuristics) to performance perspective (breaking every single performance prediction microproceesor feature). Additionally, SMC is really hard to debug (check gdb, and --smc-check in valgrind) and easy to crash (I have too vast experience with this). I really don't see enough benefits. El jue., 4 de oct. de 2018 a la(s) 21:35, Matthew Fioravante ( fmatthew5876@gmail.com) escribi=C3=B3: > One big area where dynamic languages are way ahead of C++ is runtime > dynamic code generation or self modifying code. > > > One tiny example is singleton initialization. The only safe way in C++ to > do non-constexpr singletons is by lazy init. > > The problem with lazy init is that you have to pay for a branch on every > access, and that usually involves an atomic check. > > What if you instead you atomically overwrote the check with NOPS. Then th= e > branch is gone and accessing the object is as efficient as if it weren't > lazy. > > Has anyone considered writing proposals for improving runtime code gen > with C++? > > -- > You received this message because you are subscribed to the Google Groups > "ISO C++ Standard - Future Proposals" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to std-proposals+unsubscribe@isocpp.org. > To post to this group, send email to std-proposals@isocpp.org. > To view this discussion on the web visit > https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/4489f889-977= c-45f2-8a2f-186ee3b06bff%40isocpp.org > > . > --=20 Who=E2=80=99s got the sweetest disposition? One guess, that=E2=80=99s who? Who=E2=80=99d never, ever start an argument? Who never shows a bit of temperament? Who's never wrong but always right? Who'd never dream of starting a fight? Who get stuck with all the bad luck? --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/CAFdMc-0gqidWj79ogvg8wdwx28N0N%2Bweecu%2B1dFe5mE= zyLN9gg%40mail.gmail.com. --000000000000ae03de0577731b2e Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
No, just please don't.

=
SMC has tons of consequences, from security perspective (check https://en.wikipedia.org/wiki/W%5E= X and also triggering antivirus heuristics) to performance perspective = (breaking every single performance prediction microproceesor feature).
Additionally, SMC is really hard to debug (check gdb, and --smc-check= in valgrind) and easy to crash (I have too vast experience with this).
I really don't see enough benefits.

El jue., 4 de oct. de 2018 a la(s) 21:= 35, Matthew Fioravante (fmatthew5= 876@gmail.com) escribi=C3=B3:
<= div dir=3D"ltr">
One big area where dynamic languages are way ahead of = C++ is runtime dynamic code generation or self modifying code.


One tiny example is singleton initializatio= n. The only safe way in C++ to do non-constexpr singletons is by lazy init.=

The problem with lazy init is that you have = to pay for a branch on every access, and that usually involves an atomic ch= eck.

What if you instead you atomically overwrote = the check with NOPS. Then the branch is gone and accessing the object is as= efficient as if it weren't lazy.

Has anyo= ne considered writing proposals for improving runtime code gen with C++?

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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit = https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/4489f889-977c-= 45f2-8a2f-186ee3b06bff%40isocpp.org.


--
Who=E2=80=99s= got the sweetest disposition?
One guess, that=E2=80=99s who?
Who=E2= =80=99d never, ever start an argument?
Who never shows a bit of temperam= ent?
Who's never wrong but always right?
Who'd never dream of= starting a fight?
Who get stuck with all the bad luck?

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAFdMc-0gqidW= j79ogvg8wdwx28N0N%2Bweecu%2B1dFe5mEzyLN9gg%40mail.gmail.com.
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