Re: mmap stdio breaks GNU ld

[Andreas Schwab <schwab at suse dot de>]

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.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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