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Re: bin/48183: Example in man write(2) causes endless loop
The following reply was made to PR bin/48183; it has been noted by GNATS.
From: Valery Ushakov <uwe%stderr.spb.ru@localhost>
Subject: Re: bin/48183: Example in man write(2) causes endless loop
Date: Fri, 6 Sep 2013 03:41:52 +0400
> On Wed, Sep 04, 2013 at 11:30:00PM +0000, manuel%bsdstammtisch.at@localhost
> > >Number: 48183
> > >Category: bin
> > >Synopsis: Example in man write(2) causes endless loop
> > The manpage of pread says:
> > Proper loops should use
> > while ((nr = write(fd, buf, sizeof(buf))) != -1 && nr != 0)
> > which is clearly an endless loop. Say nr = 512 and the write is
> > successful, then 512 != -1 && n1 !=0 is true.
> That whole section is fud.
> It would only ever be a problem if the program had a buffer large enough.
> That is a 2GB buffer on a system with 32bit size_t!
> The application would also know that it was doing very large writes.
> In most programs the write() calls are small (relative to size_t).
> I suspect it is only a problem for systems with 16bit size_t and 32bit ptr.
> The 'partial write' support would be more useful - especially for writev().
The text is self-contradictory as using implementation-defined
behaviour (nbytes > SSZIZE_MAX) is not something you would do for
Manual should explicitly say that for nbytes > SSIZE_MAX the result is
Name of the "nr" variable suggests that the example was copy-pasted
from read(2), which is indeed the case. The loops, as written, don't
make much sense for write(2).
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