Re^2: "uninitialized value in subroutine exit" warning from CGI.pm

I don't know what's going on at subroutine exit that would trigger the warning

On subroutine return, any return values are copied. If you return a substr lvalue, this will trigger the uninit warning at this point. For example this warns:

sub f { $_[0] }
$a = f(substr(undef,0,1));
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This is behaviour I would expect, and I'm not seeing a bug.

Dave.

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Re^3: "uninitialized value in subroutine exit" warning from CGI.pm (updated) by haukex (Archbishop) on Nov 10, 2017 at 15:45 UTC
On subroutine return, any return values are copied. [emphasis mine] D'oh! Thank you for the enlightenment on a Friday afternoon ;-) Update: Yep: `$ perl -wMstrict a = \substr(undef,0); # alias via glob $b = $a; # copy $a = 'x'; # assignment __END__ Use of uninitialized value in scalar assignment at - line 2. Modification of a read-only value attempted at - line 3.` [download] And just like above, on Perls <5.16 that dies with "`Modification of a read-only value attempted at - line 1.`" (instead of `line 3`). So I should probably call the commit I referenced a bugfix! :-) Additional updates:* Expanded the code example from the original version and added (and edited) the last paragraph.	[reply] [d/l] [select]

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Re^3: "uninitialized value in subroutine exit" warning from CGI.pm (updated)
by haukex (Archbishop) on Nov 10, 2017 at 15:45 UTC

On subroutine return, any return values are copied. [emphasis mine]

D'oh! Thank you for the enlightenment on a Friday afternoon ;-)

Update: Yep:

$ perl -wMstrict
*a = \substr(undef,0);  # alias via glob
$b = $a;                # copy
$a = 'x';               # assignment
__END__
Use of uninitialized value in scalar assignment at - line 2.
Modification of a read-only value attempted at - line 3.
[download]

And just like above, on Perls <5.16 that dies with "Modification of a read-only value attempted at - line 1." (instead of line 3). So I should probably call the commit I referenced a bugfix! :-)

Additional updates: Expanded the code example from the original version and added (and edited) the last paragraph.

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