Re^2: Getting file and line number where a subroutine is declared

Perhaps another monk can explain this behavior.

\&Foo::some_sub autovivifies a sub stub at run-time (just like sub Foo::some_sub; would at compile-time).

$ perl -le'
   print(exists(&Foo::some_sub)?1:0, defined(&Foo::some_sub)?1:0);
   $x=\&Foo::some_sub;
   print(exists(&Foo::some_sub)?1:0, defined(&Foo::some_sub)?1:0);
   eval "sub Foo::some_sub { print \"foo\" }";
   print(exists(&Foo::some_sub)?1:0, defined(&Foo::some_sub)?1:0);
   $x->();
'
00
10
11
foo
[download]

As demonstrated, this permits the reference to be taken to a sub that has yet to be defined.

\&Foo::some_sub creates glob entry at compile-time.

$ perl -le'
   print(exists($Foo::{not_a_sub})?1:0);
   print(exists($Foo::{some_sub})?1:0);
   $x=\&Foo::some_sub;
'
0
1
[download]

Comment on Re^2: Getting file and line number where a subroutine is declared Select or Download Code

Replies are listed 'Best First'.
Re^3: Getting file and line number where a subroutine is declared by kyle (Abbot) on Feb 02, 2009 at 19:19 UTC
`\&Foo::some_sub` autovivifies a sub stub at run-time (just like `sub Foo::some_sub;` would at compile-time). So it will work fine as long as we don't make any reference to the sub in any compiled code that comes before the definition. `use B; $\="\n"; # line 99 'bin/some_code.pl' { no strict 'refs'; print B::svref_2object(eval q(\\*{'Foo::some_sub'}))->LINE; print B::svref_2object(eval q(\\&Foo::some_sub))->GV->LINE; } eval q{Foo::some_sub()}; package Foo; # line 23 'bin/some_file.pl' sub some_sub { warn "Got to here"; } __END__ 25 25 Got to here at 'bin/some_file.pl' line 24.` [download] Of course, string eval has a code smell, but so does `no strict 'refs'`.	[reply] [d/l] [select]
Re^4: Getting file and line number where a subroutine is declared by ikegami (Patriarch) on Feb 02, 2009 at 19:32 UTC
Symbolic refs will do instead of `eval`. `{ no strict 'refs'; my $name = 'Foo::some_sub'; print B::svref_2object(\$name)->LINE; print B::svref_2object(\&$name)->GV->LINE; $name->(); }` [download] It can be done with strict refs too. `my $glob = $::{'Foo::'}{some_sub}; print B::svref_2object(\$glob)->LINE; print B::svref_2object(\&$glob)->GV->LINE; $glob->();` [download]	[reply] [d/l] [select]