From 5681989451861378774 X-Google-Thread: f78e5,480a31feed3c6a1b X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news3.google.com!news2.google.com!newsread.com!news-xfer.newsread.com!news-feed01.roc.ny.frontiernet.net!nntp.frontiernet.net!newscon06.news.prodigy.com!prodigy.net!border1.nntp.dca.giganews.com!nntp.giganews.com!local01.nntp.dca.giganews.com!nntp.speakeasy.net!news.speakeasy.net.POSTED!not-for-mail NNTP-Posting-Date: Wed, 08 Jun 2005 01:50:01 -0500 Return-Path: X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) Delivered-To: std-c++@ucar.edu From: John Nagle User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: en-us, en, ja MIME-Version: 1.0 Newsgroups: comp.std.c++ Subject: Re: boost::shared_ptr revisited again References: <4299DE64.40403@poczta.onet.pl><3g55jqFajuhcU1@news.dfncis.de> <1118144437.192255.257840@g47g2000cwa.googlegroups.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Message-ID: X-Complaints-To: abuse@prodigy.net Organization: SBC http://yahoo.sbc.com X-UserInfo1: TSU[@I_A\S@QBQLXCJKL^_TDEB\@PD\MNPWZKB]MPXHTEPIB_NVUAH_[BL[\IRKIANGGJBFNJF_DOLSCENSY^U@FRFUEXR@KFXYDBPWBCDQJA@X_DCBHXR[C@\EOKCJLED_SZ@RMWYXYWE_P@\\GOIW^@SYFFSWHFIXMADO@^[ADPRPETLBJ]RDGENSKQQZN X-Virus-Scanned: amavisd-new at ucar.edu X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU Approved: Fergus Henderson , moderator of comp.std.c++ X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU Date: Wed, 8 Jun 2005 01:48:42 CST Lines: 47 NNTP-Posting-Host: 65.182.171.162 X-Trace: sv3-1V1RBUWGwbN1uhulX2UXifiijphHcH5OAqqt62IS033Jp080u0+8OihSMYXxoXzrqe5S1du3ccebtkS!cJNBY6REJa/y+lC/UgLTcn29z1+51sZP0+7PkAL66HF8eTZlarroce0sPCSc24IEAZZIECwKfFDJ!fer6HlLE9lVlL7eFI0WlmQW3Y4CCoLJu X-Complaints-To: abuse@speakeasy.net X-DMCA-Complaints-To: abuse@speakeasy.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.31 Xref: g2news1.google.com comp.std.c++:5027 Andrei Alexandrescu (See Website For Email) wrote: > Pete Becker wrote: > >> kanze@gabi-soft.fr wrote: >> >>> Pete Becker wrote: > But Java did eliminate all dangling pointer bugs. > > To clarify my response to the "runtime check": it is runtime, but if it > is done in hardware, it has zero time cost. My understanding of the > context of the discussion was that we were discussing that there is a > price to the "runtime check". The hardware trap mechanism costs only > silicon on the chip, and zero time. True. It's also worth noting that, with compiler support, many run-time checks can be hoisted out of loops. This is particularly effective for subscript checks. The technology to do this was developed in the Pascal era, but has to some extent been forgotten. For one Pascal compiler, it was observed that 95% of subscript checks could be optimized out. Similarly, reference count updates can sometimes be optimized out or hoisted out of loops. In both cases, though, the compiler needs to know what to look for. The compiler also has to be allowed to detect errors "early". That is, once an error becomes inevitable, the implementation can report the error. This allows hoisting subscript checks outside of loops. The notion that checking is inherently expensive comes from poor implementations. Berkeley Pascal for BSD comes to mind; it made a subroutine call for every subscript check. John Nagle Animats --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]