http://qs321.pair.com?node_id=580788


in reply to Re: Spot the bug!
in thread Spot the bug!

Localizing $@ would have protected your caller against your clobbering $@. You'd still have the alias/copy bug so now shift() would always return undef because $@ now is always blank but at least you'd be safer. When using $@, always, always, always copy it out first. The smallest piece of code can go clobber $@ so you should always copy it out before examining it.

sub foo {
    local $@;
    return eval { bar( shift ) } || 0;
}

[download]

⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊

Replies are listed 'Best First'.
Re^3: Spot the bug!
by tlm (Prior) on Oct 27, 2006 at 00:49 UTC

    Agreed. But what about just using @_ = @_ instead of local @_? Assignment to @_ is what the docs prescribe for breaking the aliasing. Any reason for preferring one approach over the other?

    the lowliest monk

[reply]
[d/l]
[select]

      I said local $@, not @_. There's no point to localizing @_, that's your input! You'd copy stuff out of it if you needed that behavior.

      ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊

[reply]
[d/l]

In Section Meditations