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Re: fseek064 calling fflush on Cygwin

Brian Ford <Brian.Ford <at>> writes:

> I have an application that is having a 64-bit file I/O problem with Cygwin
> 1.7.0 CVS that it did not have with Cygwin 1.5.18.  I have tracked it
> down to the following series of calls in newlib:
> #0  fflush (fp=0x7b5a764)
>     at ../../../../../cygwin/newlib/libc/stdio/fflush.c:124
> #1  0x611049ff in _fseeko64_r (ptr=0x16cbd008, fp=0x7b5a764,
>     offset=27368291304, whence=0)
>     at ../../../../../cygwin/newlib/libc/stdio64/fseeko64.c:326
> #2  0x61104edf in fseeko64 (fp=0x7b5a764, offset=27368291304, whence=0)
>     at ../../../../../cygwin/newlib/libc/stdio64/fseeko64.c:350

Thanks for the report.  Prior to a couple months ago, this wasn't a problem, 
because fseek(f,0,SEEK_END) was mistakenly succeeding on large files.  This is 
fallout from my recent patch to make fseek properly fail with EOVERFLOW; but as 
you discovered, a side effect is that fflush is no longer seeking to the end 
the way it should be when it ignores the EOVERFLOW.

> So, it would seem that fflush is not 64 bit safe and fseeko64 should not
> be calling it, but I'm not sure how to fix it.
> Any suggestions?

In environments with large files, fflush needs to check for __SL64, in which 
case it should call fp->_seek64, not fp->_seek.  That clinches it - I need to 
complete my patch to make fflush reentrant and 64-bit safe.  I'll hopefully 
have something by early next week.

Eric Blake

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