Re^3: Contents of @_ using subroutine signatures with default values (flag)

The simplified answer: no, it's not that simple. If @_ isn't populated, then the signature code gets its arguments directly from the stack. If @_ gets populated, then the stack and @_ can get out of sync, e.g. by code within the signature which manipulates @_. So in that case the code must get its args from @_ rather than from the stack. So there have to be two code paths for everything.

See this p5p post for more details.

Dave.

Comment on Re^3: Contents of @_ using subroutine signatures with default values (flag)

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Re^4: Contents of @_ using subroutine signatures with default values (flag) by LanX (Saint) on Jul 14, 2020 at 10:21 UTC
> See this p5p post for more details. Thanks Dave, I will. ... this will be a longer read this evening. OO On a side note: I was fascinated to learn (rediscover ?), that a call `&sub` without arguments has full access to the callers @_. `use strict; use warnings; use Data::Dump qw/pp dd/; sub foo { warn pp \@_; push @_,@_+1 } sub tst { &foo; &foo; &foo; warn pp \@_; } tst(1);` [download] `-- mode: compilation; default-directory: "d:/exp/" -- Compilation started at Tue Jul 14 12:21:10 C:/Perl_524/bin\perl.exe -w d:/exp/access_@_.pl [1] at d:/exp/access_@_.pl line 7. [1, 2] at d:/exp/access_@_.pl line 7. [1, 2, 3] at d:/exp/access_@_.pl line 7. [1 .. 4] at d:/exp/access_@_.pl line 15. Compilation finished at Tue Jul 14 12:21:10` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]

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Re^4: Contents of @_ using subroutine signatures with default values (flag)
by LanX (Saint) on Jul 14, 2020 at 10:21 UTC

> See this p5p post for more details.

Thanks Dave, I will.

... this will be a longer read this evening. OO

On a side note: I was fascinated to learn (rediscover ?), that a call &sub without arguments has full access to the callers @_.

use strict;
use warnings;
use Data::Dump qw/pp dd/;


sub foo {
    warn pp \@_;
    push @_,@_+1
}

sub tst {
    &foo;
    &foo;
    &foo;
    warn pp \@_;
}

tst(1);
[download]

-*- mode: compilation; default-directory: "d:/exp/" -*- Compilation started at Tue Jul 14 12:21:10 C:/Perl_524/bin\perl.exe -w d:/exp/access_@_.pl [1] at d:/exp/access_@_.pl line 7. [1, 2] at d:/exp/access_@_.pl line 7. [1, 2, 3] at d:/exp/access_@_.pl line 7. [1 .. 4] at d:/exp/access_@_.pl line 15. Compilation finished at Tue Jul 14 12:21:10
[download]

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

[reply]
[d/l]
[select]