Re: Analysis of libstdc++/2071 test case

[Loren James Rittle <rittle at latour dot rsch dot comm dot mot dot com>]

Peter Schmid <schmid@snake.iap.physik.tu-darmstadt.de> writes:

> First of all, I like to thank you for your excellent analysis of the
> problem.  I can confirm that reading from cin produces illegal seeks. 

You are quite welcome.

> If I add some error checking to your second code, check the value of
> errno, and run the resulting program compiled by gcc version 3.1
> 20010508 (experimental) on i686-pc-linux-gnu (glibc 2.2).

[...]

> The output is as follows:
> ./a.out
> 1234
> Illegal seek
> 1 2 29

Yes, I had noticed that Linux also considers the fseek on stdin to be
illegal but it appears to not flush the input buffer as is done on BSD
and (guessing since I didn't look as closely and have no OS source
code) Solaris.

> I see no reason why the call to fseek is not dropped when reading from
> stdin.

Unfortunately, those fseeks appear to be in the code for a reason and
blinding dropping them may not be a good idea.  I am learning the code
so I can develop a patch.

Regards,
Loren