220 39311 <5a247f18-6cf7-4b92-8572-877c6ffc8da4@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Russell Johnston Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Alternative proposal for mapping P0709 Deterministic Exceptions into C Date: Mon, 23 Jul 2018 10:34:04 -0700 (PDT) Lines: 74 Approved: news@gmane.org Message-ID: <5a247f18-6cf7-4b92-8572-877c6ffc8da4@isocpp.org> References: <6a65c934-5d2a-4e75-b88d-9eaaee338bd3@isocpp.org> <87240a3d-623f-4f7f-8e7c-fa8c9482fa72@isocpp.org> <5a449c86-b0f4-4b07-b5d6-21b7adbfd63b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_8239_978675479.1532367244429" X-Trace: blaine.gmane.org 1532367120 5556 195.159.176.226 (23 Jul 2018 17:32:00 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 23 Jul 2018 17:32:00 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCFPHMELQABRBDND3DNAKGQESBPZHJI@isocpp.org Mon Jul 23 19:31:56 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f200.google.com ([209.85.161.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fhegd-0001LP-FO for gclcip-std-proposals@m.gmane.org; Mon, 23 Jul 2018 19:31:55 +0200 Original-Received: by mail-yw0-f200.google.com with SMTP id 2-v6sf654685ywn.13 for ; Mon, 23 Jul 2018 10:34:06 -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=wGxIz2XJXyYSWILRq4hBziCwaDTzTM2XIi/MhO1li+s=; b=eX90G0X7ZfPUiRz+GP6o2G6UEgGEb+o2aZ9bUR61fhkiThJ8AjcGxa+9h4gY+7MToq p+aGNtQ0pS4vMvGiX77+4+vsa/vEpQjJfutgGjTwfwFqIVAY0BJ6FLchvM/sSAJmzLNH akynor3wXKbw7QuE59Te3Ya3JZj5LNN4HiUENe/P64LwxF1gf6LfeezfJqGvuxJaVpJp a1PgdF6hD5NjasL8RyBrsPPWUzyeWsYfkLrvkrqndds00MB11Ds2ZuwCsX6W1Ye918ET 2JRd5PXytD7XXE6ZYg3/0HvBwbEZopmtJTdmfA/0SUpFdmqXQleR0OgmDzvVTmGCMaxg FNfw== 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=wGxIz2XJXyYSWILRq4hBziCwaDTzTM2XIi/MhO1li+s=; b=qs8eLYeNVdNLoWIQK5ierFqmhCSH4IoircSN1YxDzRQAPFQJ6Y/qxyRgiHsnAktbkx kKS/x3uY+prvpXBS1cOWUc1JN+6a7j+I5o66R1j/jGZHWUsaBm+Ict/w4rFdKQGLj9gR 98WoygwGKJwt/f+HT6+Tu6vTFpLObiNqffXyjMoTPvPULVi6a7rF9wBdD50Fj04z00D/ TcR2rIZGnMHZhqi3AlVRjuCCm/9F97fQJQ1y+bfObneTDsU9V+YZKwEp10LLM/myfIUJ VWMZ0v401sED13leBZtIB/5oJuiliEVYn1sZK8jlmIGXoYXAxju4pHiV4nmmCbp02gJS 7T9Q== 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=wGxIz2XJXyYSWILRq4hBziCwaDTzTM2XIi/MhO1li+s=; b=d2qcNBLzPMkSoLpxVyTTqHWdrm4hazR5S8YV/klw8HepGaFs9Xu6MBC8VxLPPgEmDN nu6CIBS3FCoOKXvIl0VkTbs0+CZQqBel0LTMlzXQurIQR3Umgv+VkA19wFPYoIs2GvLl f+PphVtRwTwqC2gM0nQ54V81Q4821YFdLw4Ee2dy1AAoScRp6MDT2ZnGnQTLBQ4dB7SQ cchk90/xHVZ41fVy/Kri4heBeewsnXo85mPtUEmejOf9ioUVqvumOX6HDhzbV4dF1isy 53U9Vj0Ky1HUOo4WOg9rL4a5WWM9lFUd7tjiMtnPWILxNzbsMG3KMq1KKrP6sF7ZGiiB S0OA== X-Gm-Message-State: AOUpUlE6ToYs12ZLNImSgfvlbRJ1CFEVtRS5FOE/VICq5JQ8VNNR3EM/ TLgW4huQqxfvO1wjkfpMMnYWVQ== X-Google-Smtp-Source: AAOMgpcHi4nwS2UxcDDe9sB57ZHKMpyXDPtJ5Pbnlc18GU0urBHimHrs5U2iTyDE1KbEuQZu3vVY4w== X-Received: by 2002:a25:2e02:: with SMTP id u2-v6mr3963526ybu.55.1532367246042; Mon, 23 Jul 2018 10:34:06 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a0d:cc46:: with SMTP id o67-v6ls1099861ywd.8.gmail; Mon, 23 Jul 2018 10:34:05 -0700 (PDT) X-Received: by 2002:a81:78c6:: with SMTP id t189-v6mr265452ywc.7.1532367244930; Mon, 23 Jul 2018 10:34:04 -0700 (PDT) In-Reply-To: X-Original-Sender: rpjohnst@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:39311 Archived-At: ------=_Part_8239_978675479.1532367244429 Content-Type: multipart/alternative; boundary="----=_Part_8240_53264138.1532367244429" ------=_Part_8240_53264138.1532367244429 Content-Type: text/plain; charset="UTF-8" On Monday, July 23, 2018 at 10:30:13 AM UTC-7, Marcin Jaczewski wrote: > > On RISC-V then cost will be same to `bool foo(void* ret)`. This will be > still "zero overhead", simply for other architectures it will be "negative > overhead" compared to equivalent manual checks in code. > > Another way could be use RVO-like calling convention. Place for return > union with discriminant will be pass as one pointer to function, this > storage could even be reused by next function if it return same error type. > A third option is to match the behavior of other platforms, and store the discriminant in an extra register. There should already be plenty of caller-saved registers in the ABI, used primarily for passing arguments- their use could be extended to the return value's discriminant. This would also be "negative overhead" compared to passing a pointer. -- 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/5a247f18-6cf7-4b92-8572-877c6ffc8da4%40isocpp.org. ------=_Part_8240_53264138.1532367244429 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Monday, July 23, 2018 at 10:30:13 AM UTC-7, Mar= cin Jaczewski wrote:

On RISC-V then cost will be same to `bool fo= o(void* ret)`. This will be still "zero overhead", simply for oth= er architectures it will be "negative overhead" compared to equiv= alent manual checks in code.

Another way could be = use RVO-like calling convention. Place for return union with discriminant w= ill be pass as one pointer to function, this storage could even be reused b= y next function if it return same error type.
=
A third option is to match the behavior of other platforms, = and store the discriminant in an extra register. There should already be pl= enty of caller-saved registers in the ABI, used primarily for passing argum= ents- their use could be extended to the return value's discriminant. T= his would also be "negative overhead" compared to passing a point= er.

--
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/5a247f18-6cf7-4b92-8572-877c6ffc8da4= %40isocpp.org.
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