Bug#1016369: IO::Handle ->error does not work, always saying "fine"

[Ian Jackson]

Package: perl
Version: 5.34.0-4
Severity: grave

To reproduce

    perl -MIO::Handle -e 'open X, "<", "." or die $!; $_ = <X>; printf "%s %s %s\n", X->error(), $!;'
    perl -MIO::Handle -e 'open X, ">", "/dev/full" or die $!; print X 1; flush X; printf "%s %s %s\n", X->error(), $!; close X'

Expected output

    -1 Bad file descriptor
    -1 No space left on device

Actual output

    0 Bad file descriptor
    0 No space left on device

This is quite alarming.  I think it makes it in fact impossible to
read files fully reliably in Perl.  "use autodie" does not seem to help.

And scripts might reasonably have expected that they could defer error
handling by testing error() rather than each call (as one can in C).

I think this used to work, but, evidently, only in the distant past,
since my jessie chroot doesn't get this right either.

Justification for the severity:

Can cause data loss: if a file is opened but unreadable for any
reason, the program will process the part (if any) that will is
readable and then 

Ian.

-- 
Ian Jackson <ijackson at chiark.greenend.org.uk>   These opinions are my own.  

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