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Re: mmap stdio breaks GNU ld
Paul Eggert <eggert@twinsun.com> writes:
|> > Date: Tue, 22 Jan 2002 02:13:31 -0600
|> > From: Mark Brown <bmark@us.ibm.com>
|>
|> > Yes, POSIX doesn't make clear that "the position indicated by the
|> > file offset" could be anywhere".
|>
|> That's being generous, as POSIX obscures the issue so much that light
|> barely escapes. For example, here's a quote from the POSIX 1003.1-2001
|> section "Interaction of File Descriptors and Standard I/O Streams":
|>
|> * If any previous active handle has been used by a function that
|> explicitly changed the file offset, except as required above for
|> the first handle, the application shall perform an lseek( ) or
|> fseek( ) (as appropriate to the type of handle) to an appropriate
|> location.
|>
|> I still can't parse the phrase "except as required above for the first
|> handle", and I've read the context several times.
It refers to the items above the last paragraph, where it states what you
have to do before you can use a file description through a second handle.
There it says, that if you have an input or update stream you need to call
either fflush (if defined at all, I would add) or fclose on it. In other
words, you don't need to call fseek again after fflush, this is the
exception as described in your quote.
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse.de
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