220 40243 <94d79dd7-ba3b-4bf8-91ed-e5dc02b33670@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: florian.csdt@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: more security concerns Date: Fri, 28 Sep 2018 07:14:20 -0700 (PDT) Lines: 236 Approved: news@gmane.org Message-ID: <94d79dd7-ba3b-4bf8-91ed-e5dc02b33670@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_358_140688532.1538144060833" X-Trace: blaine.gmane.org 1538143937 327 195.159.176.226 (28 Sep 2018 14:12:17 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 28 Sep 2018 14:12:17 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC26HM4V3MIRBPPOXDOQKGQETRXATYQ@isocpp.org Fri Sep 28 16:12:12 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb1-f198.google.com ([209.85.219.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g5tV6-0008RT-3j for gclcip-std-proposals@m.gmane.org; Fri, 28 Sep 2018 16:12:12 +0200 Original-Received: by mail-yb1-f198.google.com with SMTP id i11-v6sf3337147yba.8 for ; Fri, 28 Sep 2018 07:14:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=Vbm/d1i6fgL6UPLr6a9wLZZLeJrD3TCkf4s9Y9vvBcE=; b=v4KUqUZdSJ1D3zQB7vFXyTf5/n6uZdznRZvB6lNsLdAU8v8Rmrp9mKkimnczYUVtgq sfCLeBwHsAaFtesDmbyw/e+3DZaz1Yok2JOITPnpOqOzkzHwNI+bP29tyODK7o0iyupL Gn0IWw+tu3yceqX2ViUO6elkK4E/Okfl8ESXYzFbw92EiKIu1uGtotB2Q9sOgUlfbScC gnF82/wHN+526cmsWBk89VJq6TcbdAa4RH/x+JtRImexCr+/rLbLlUDZPWnx8kyfhJZF N5n5FRpiJ1Hzyd/abAS75I/Rxqcq+Y+xmmEQZ8p+hdYt4Mf3i7cM0UljMaQUL73vTTHn IE7Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=Vbm/d1i6fgL6UPLr6a9wLZZLeJrD3TCkf4s9Y9vvBcE=; b=tTBAEBb6RHF+IVF+mbWver2Lbcjut85+HolWz2g2m2xnzqnr5+Tclilj6HWRYBqK79 1C0f+cW/Fgep7B4c5iu2jbDynWl9k7z6D4wQoxCwqcE+ddBeHrw1deBTbQfxQ2+MFW1W JQdKU3gbGfjCUA48WBmKRNJeISO50lSts9wqzv0l048yL38/NMvBtJgpfzYoxLTv35Po VJPYXsLkge6N1HfAmsh1nwTEDse5af7AEfGZKiOpd56FIaZS8NBFF2akS4dlYZi1iCQJ iwuAn+u+o+WcqengCjW+UiPKcxez2gTMLiCFI1YSPgXfYk7HPXWWJGeV9qhzW9KnUkWs ypFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=Vbm/d1i6fgL6UPLr6a9wLZZLeJrD3TCkf4s9Y9vvBcE=; b=H/zQ+mD5oNPlqGlCQy+Wd5V8bMuQA02aXtXwfQyWqT996O720/jTa9J/GyZR1gSDfL jIYXxdScgKeP821itSK1/Zud+qhiNecaoVN7WHGr4ffaGNZTnxjVVuAP44g2wOI12c+N cy/uJeU6pZnhEtl7GRHgIwoo4k7BSjghKn6mSHgyVy1ZAv0L85c0HRXaDpfvbeU3XjTy NdWxQQ+/YBuE1n4Xhfi+DQVmw8jxDoMC5drhN4sSnnAFED/Nfsci4qyiV9pDTHeDSSiT 6U6CcHd3ZVZxq/3XhvmkBDCWnGkFt2Bwj/TxQayChoEImmzjln+WWVa7zPURiSUMaAsv m3UQ== X-Gm-Message-State: ABuFfoio6wYJrJ7P5scEAOd8gDUFiitB+dHm03TBHRS4FQQayNiFGiPY flVHLxXlLisT7CdNzEjkTWtMLg== X-Google-Smtp-Source: ACcGV62lz2wK/YjkFYsTwR5QA9sJHJtSuOyiqCBLyz8pOaij994WoNY1Um9UpLSZKrLV80zvOU6thw== X-Received: by 2002:a25:7651:: with SMTP id r78-v6mr5052643ybc.57.1538144062464; Fri, 28 Sep 2018 07:14:22 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a81:1d85:: with SMTP id d127-v6ls2585220ywd.11.gmail; Fri, 28 Sep 2018 07:14:21 -0700 (PDT) X-Received: by 2002:a81:78c6:: with SMTP id t189-v6mr165965ywc.7.1538144061269; Fri, 28 Sep 2018 07:14:21 -0700 (PDT) In-Reply-To: X-Original-Sender: florian.csdt@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:40243 Archived-At: ------=_Part_358_140688532.1538144060833 Content-Type: multipart/alternative; boundary="----=_Part_359_2102590875.1538144060833" ------=_Part_359_2102590875.1538144060833 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I want to highlight that [[nodiscard]] on functions is not about forcing=20 the compiler to keep the value, but instead to emit a warning if the user= =20 doesn't use the value. So meaning would be different. In that respect, another attribute name might be better. Also, it is already possible (but cumbersome) to implement already without= =20 volatile: void f() { int secret_int; float secret_float; /* ... */ secret_int =3D 0; secret_float =3D 0 asm volatile ("" ::"irm"(secret_int), "xm"(secret_float)); } I would really like an attribute for that, though. Le vendredi 28 septembre 2018 15:36:42 UTC+2, Daniel Gutson a =C3=A9crit : > > Yeah. But please note that this is not only for function calls. > > void f() > { > int secret; > .... > secret =3D 0; //removed due to DSE > } > > If I declare secret as volatile or write 0s to its address I may prevent= =20 > the compiler to use a register impacting in performance. That's why I wan= t=20 > to use the attribute here too. > > > > El vie., 28 sept. 2018 10:32, Andrew Giese > escribi=C3=B3: > >> I like the idea. >> Function poisoning might also serve your needs. E.g.,=20 >> https://www.fluentcpp.com/2018/09/04/function-poisoning-in-cpp/ >> >> If gcc poison were standardized in some fashion, you could write your ow= n=20 >> wrappers to those functions with all the [[nodiscard]] you might want. >> >> Control in that case is a little less granular, indeed. Probably if=20 >> you're writing [[nodiscard]] on a per-expression basis you are not=20 >> discarding the result already. >> >> Regards >> >> --=20 >> You received this message because you are subscribed to the Google Group= s=20 >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n=20 >> email to std-proposal...@isocpp.org . >> To post to this group, send email to std-pr...@isocpp.org . >> To view this discussion on the web visit=20 >> https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAO8_tC4kNZ= 6s-xMXo69n1D3dbOMkqt0fjLU44Uq5TfABp17hQQ%40mail.gmail.com=20 >> >> . >> > --=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/94d79dd7-ba3b-4bf8-91ed-e5dc02b33670%40isocpp.or= g. ------=_Part_359_2102590875.1538144060833 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I want to highlight that [[nodiscard]] on functions is not= about forcing the compiler to keep the value, but instead to emit a warnin= g if the user doesn't use the value.
So meaning would be different.<= br>In that respect, another attribute name might be better.

Also, it= is already possible (but cumbersome) to implement already without volatile= :
voi= d <= span style=3D"color: #000;" class=3D"styled-by-prettify">f() {
=C2=A0 int secret_int;
=C2=A0 float secret_float;=
=C2=A0 /* ... */=
=C2=A0 secret_int =3D 0;
=C2=A0 secret_floa= t =3D 0
=C2=A0 asm volatile ("" = ::"ir= m"(secret_int), "xm"(secret_float));
}

I would really li= ke an attribute for that, though.


Le vendredi 28 septembre 2018 = 15:36:42 UTC+2, Daniel Gutson a =C3=A9crit=C2=A0:
Yeah.=C2=A0 But please note that = this is not only for function calls.

void f()
{
=C2=A0 =C2= =A0int secret;
=C2=A0 =C2=A0....
=C2=A0 =C2=A0secret =3D 0;=C2=A0 //removed due to DSE
}

If I declare sec= ret as volatile or write 0s to its address I may prevent the compiler to us= e a register impacting in performance. That's why I want to use the att= ribute here too.



El vie., 28 sept. 2018 10:32, Andrew Giese <<= a href=3D"javascript:" target=3D"_blank" gdf-obfuscated-mailto=3D"luZjexPSA= AAJ" rel=3D"nofollow" onmousedown=3D"this.href=3D'javascript:';retu= rn true;" onclick=3D"this.href=3D'javascript:';return true;">gies..= ..@gmail.com> escribi=C3=B3:
=
I like the idea.
Function poisoning= might also serve your needs. E.g.,=C2=A0https://www.fluentcpp.com/2018/09/04/function-poisoni= ng-in-cpp/

If gcc po= ison were standardized in some fashion, you could write your own wrappers t= o those functions with all the [[nodiscard]] you might want.

Control in that case is a little less= granular, indeed. Probably if you're writing [[nodiscard]] on a per-ex= pression basis you are not discarding the result already.

Regards

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