Re^2: Inlining a "lexically-scoped scalar which has no other references"

thx, ikegami these are pretty much all the tests I already ran. 8-|

I think it's an old optimization feature that got dropped/lost, without updating the docs.

If anyone has access to a fairly old perl5 version, it would be nice to know what these test produce... He doesn't need to use B::Concise, it's documented that redefining a "constant function" always has to give a warning!

so plz, just run this code, and check for a warning:

no warnings;

my $lex = 4;         # file scoped lexical

#--- normal
# inner scope
sub with_proto ()  { my $lex }

# outer scope
{
  my $lex = 4; 
  sub with_proto() { $lex } 
}

# file scope
sub with_proto()  { $lex }

#--- reference
# inner scope
sub with_proto()  {\ my $lex }

# outer scope
{
  my $lex = 4; 
  sub with_proto() {\ $lex } 
}

# file scope
sub with_proto()  {\ $lex }


#------ lvalue

#--- normal
# inner scope
sub with_proto() :lvalue { my $lex }

# outer scope
{
  my $lex = 4; 
  sub with_proto() :lvalue { $lex } 
}

# file scope
sub with_proto() :lvalue { $lex }

#--- reference
# lvalue references are not feasible, because of
#   "Can't modify single ref constructor in lvalue subroutine"




#------ overriding constant function throws always a warning
sub with_proto () {4} 

# uncommenting garanties a warning
# sub with_proto () {5}
[download]

Cheers Rolf

Comment on Re^2: Inlining a "lexically-scoped scalar which has no other references" Download Code

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Re^3: Inlining a "lexically-scoped scalar which has no other references" by ikegami (Patriarch) on Sep 28, 2009 at 02:00 UTC
The oldest I have is 5.6.0, but it doesn't give a warning even when uncommenting the last line. Changing `no warnings;` to `use warnings;` shows that the following creates a constant in 5.6.0 and 5.6.1, but not in 5.8.0: `sub with_proto () { my $lex }` [download] >c:\progs\perl560\bin\perl test.pl Use of uninitialized value at test.pl line 12. Constant subroutine with_proto redefined at test.pl line 12. Subroutine with_proto redefined at test.pl line 16. Subroutine with_proto redefined at test.pl line 20. Subroutine with_proto redefined at test.pl line 25. Subroutine with_proto redefined at test.pl line 29. Subroutine with_proto redefined at test.pl line 36. Subroutine with_proto redefined at test.pl line 41. Subroutine with_proto redefined at test.pl line 45. Subroutine with_proto redefined at test.pl line 55. Constant subroutine with_proto redefined at test.pl line 58. >c:\progs\perl561\bin\perl test.pl Use of uninitialized value at test.pl line 12. Constant subroutine with_proto redefined at test.pl line 12. Subroutine with_proto redefined at test.pl line 16. Subroutine with_proto redefined at test.pl line 20. Subroutine with_proto redefined at test.pl line 25. Subroutine with_proto redefined at test.pl line 29. Subroutine with_proto redefined at test.pl line 36. Subroutine with_proto redefined at test.pl line 41. Subroutine with_proto redefined at test.pl line 45. Subroutine with_proto redefined at test.pl line 55. Constant subroutine with_proto redefined at test.pl line 58. >c:\progs\perl580\bin\perl test.pl Subroutine with_proto redefined at test.pl line 12. Subroutine with_proto redefined at test.pl line 16. Subroutine with_proto redefined at test.pl line 20. Subroutine with_proto redefined at test.pl line 25. Subroutine with_proto redefined at test.pl line 29. Subroutine with_proto redefined at test.pl line 36. Subroutine with_proto redefined at test.pl line 41. Subroutine with_proto redefined at test.pl line 45. Subroutine with_proto redefined at test.pl line 55. Constant subroutine with_proto redefined at test.pl line 58. [download] Update: I identified the wrong one. Fixed.	[reply] [d/l] [select]
Re^4: Inlining a "lexically-scoped scalar which has no other references" by ikegami (Patriarch) on Sep 28, 2009 at 02:09 UTC
How does one use that?!?!	[reply]
Re^5: Inlining a "lexically-scoped scalar which has no other references" by LanX (Saint) on Sep 28, 2009 at 02:21 UTC
Well the question "what for" was the next after identfying "what is it"... (I hoped to find a new black magic gadget to play with ;-) I think the intended logic was "if optimization produces a constant return value, then the value will be inlined"! Is this a now bug or is it just deprecated and the docs are out of phase? Consequently: Do I have to start perlbug or do I have to send a mail to pod-people...? Cheers Rolf	[reply]
Re^6: Inlining a "lexically-scoped scalar which has no other references" by ikegami (Patriarch) on Sep 28, 2009 at 02:56 UTC