Re^2: Testing for read() failures on different platforms

What on earth would generate a read failure?

Networked file systems, corrupt media, broken pipe, etc. Not checking for read errors can lead to evil bugs :-)

As to the OPs question:

... can anyone advise me on a better way for testing cross platform read failures?

I find redefining read is the simplest solution. At its most basic just adding

BEGIN {
    *CORE::GLOBAL::read = sub (*\$$;$) { return undef };
};
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to your test file will always cause read to fail.

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Re^3: Testing for read() failures on different platforms by leriksen (Curate) on Jul 28, 2004 at 01:06 UTC
Yep, of course. And nicely extensible to other functions in the CORE package I imagine, like testing failing write()'s, etc. That is the solution I will use. Thank you +++++++++++++++++ #!/usr/bin/perl use warnings;use strict;use brain;	[reply]
Re^3: Testing for read() failures on different platforms by leriksen (Curate) on Jul 28, 2004 at 07:13 UTC
Bugger, that doesn't work, and it behaves funny too. Here's the code in the File.t file `... $file = File->new('t/file7.test'); eval { # declare as local so default is restored on block exit local CORE::GLOBAL::read = sub (\$$;$) { return undef }; $file->header(); }; ...` [download] And File::header() looks like this ... sub header { my ( $self ) = @_; my $seek_rc = $self->{FH}->seek($self->{Header}->{OFFSET}, SEEK_SE +T ); if ($seek_rc == 0) { croak( 'Cannot seek to absolute file position on opened file handl +e - ', $! ); } my $length = $self->{FH}->read(my $header, $self->{Header}->{Lengt +h}); # check if read() had an error croak( "Error in reading file header - $!") # pathological test unless defined $length; croak( 'Error in reading file header - Mismatch between expected l +ength (', $self->{Header}->{Length}, ") and returned length ($length +) byte count") unless $length == $self->{Header}->{_Length}; $header =~ s/(?:\015+)?\012.$/\n/; # remove any garbage at end +of header and replace with \n return $header; } ... [download] So if the read() returns undef, I expect the croak() message to appear with the $! reason for failure. Instead, I don't get my croak() message , all I get is $! populated with 'Bad file descriptor'. $@ is empty (that us , $@ eq ''). Whatsmore, this happens on Linux. Both $@ and $! are still an empty string on Solaris. So why aren't I croak()'ing ? use brain;*	[reply] [d/l] [select]