Bug#98430: perl: Can't C<goto &func> at end of lvalue sub

[Dominic Hargreaves]

found 98430 5.14.0-1
notforwarded 98430
thanks

On Thu, May 24, 2001 at 05:28:38PM +1000, Brendan O'Dea wrote:
> [Full bug report details are at http://bugs.debian.org/98430.  Please
>  retain 98430-forwarded at bugs.debian.org in the Cc field of replies.]
> 
> Summary:  A module which worked with 5.6.0 now chokes under 5.6.1 with a
> compile-time error on goto& from an lvalued subroutine.
> 
> Here's a small example program:
> 
>     package Bug;
>     $value = 'none';
>     sub a :lvalue        { $value }
>     sub b :lvalue        { goto &a }
>     sub AUTOLOAD :lvalue { goto &a }
>     b()      = 'sub'         if grep /^sub/,         @ARGV;
>     c()      = 'auto-sub'    if grep /^auto-sub/,    @ARGV;
>     Bug->b() = 'method'      if grep /^method/,      @ARGV;
>     Bug->d() = 'auto-method' if grep /^auto-method/, @ARGV;
>     print "$value\n";
> 
> Note that if the AUTOLOAD in this example instead contains
> 
>     *$AUTOLOAD = sub :lvalue { $value };
>     goto &$AUTOLOAD;
> 
> which is closer to the code described in the bug report, the behaviour
> is unchanged.  Under 5.6.0, the following occurs:
> 
>     $ perl -w bug 
>     none
>     $ perl -w bug sub
>     sub
>     $ perl -w bug auto-sub
>     Can't modify non-lvalue subroutine call at bug line 7.
>     $ perl -w bug method
>     method
>     $ perl -w bug auto-method
>     auto-method
> 
> So there's only one case which doesn't work, where a non-method AUTOLOAD
> is called and the exception occurs at run-time.
> 
> The code doesn't compile under 5.6.1:
> 
>     $ perl -w bug
>     Can't modify goto in lvalue subroutine return at bug line 4, near "&a }"
>     BEGIN not safe after errors--compilation aborted at bug line 5.
> 
> Basically any goto& within an :lvalue subroutine fails.

After 10 years, this test program still doesn't work. There was
no follow-up from p5p to this post. I'm inclined to think that this
was an unfortunat backwards-incompatible change made in 5.6.1, but that
it's quite unlikely to be changed now. Any objections to be me closing
this?

-- 
Dominic Hargreaves | http://www.larted.org.uk/~dom/
PGP key 5178E2A5 from the.earth.li (keyserver,web,email)