220 40202 <0766c3b4-2f95-4c3a-a716-5b868551ecec@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Alberto Barbati Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Should istream::read() be allowed to clobber the buffer beyond the file's size. 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The same goes for the C function fread(). > > I'm unsure if the standard actually allows this behaviour. Microsoft=20 > recently changed the behaviour and it broke our test programs. > > Microsoft claims this is allowed, I think it is not logical to allow it. > > Is this behaviour allowed?=20 > This is the relevant part of the standard:=20 http://eel.is/c++draft/istream.unformatted#30 It's not specifically allowed nor denied, so I guess it could be=20 interpreted to allow the Microsoft implementation. If it is allowed, should it be? > If it allows a significant optimization, as stated by the Microsoft=20 developers involved, definitely it should, in my opinion. Accessing the=20 rest of the buffer pretending that it did not get overwritten is such a=20 special and, no offense, rather useless scenario. I much rather prefer to= =20 have the main scenario optimized than having a specific corner case=20 "correct". Again, that's my opinion. --=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/0766c3b4-2f95-4c3a-a716-5b868551ecec%40isocpp.or= g. ------=_Part_725_1483955140.1537513532904 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Il giorno gioved=C3=AC 20 settembre 2018 00:06:34 UTC+2, B= engt Gustafsson ha scritto:
When you do a read on an istream with a buffer larger than th= e file (in text mode) the MSVC was recently changed so that it may change b= ytes in the buffer after the file length. The same goes for the C function = fread().

I'm unsure if the standard actually allows = this behaviour. Microsoft recently changed the behaviour and it broke our t= est programs.

Microsoft claims this is allowed, I = think it is not logical to allow it.

Is this behav= iour allowed?

This is the = relevant part of the standard: http://eel.is/c++draft/istream.unformatted#3= 0

It's not specifically allowed nor denied, so= I guess it could be interpreted to allow the Microsoft implementation.

=
If it is allowed, should it be?

= If it allows a significant optimization, as stated by the Microsoft develop= ers involved, definitely it should, in my opinion. Accessing the rest of th= e buffer pretending that it did not get overwritten is such a special and, = no offense, rather useless scenario. I much rather prefer to have the main = scenario optimized than having a specific corner case "correct". = Again, that's my opinion.

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