Re^4: Disabling runtime warnings in dynamic scope?

... and a local $^W = $my_bits doesn't change them at runtime for scopes further down ...

What do you mean? This works fine:

use strict;

my $lasthash = {
    lastfunc => sub { last ; },
} ;

sub lastfunc {
    last ;
}

sub test {
    # local ($^W) = 1 ; # Activate this line to display the warnings
    while(1) { lastfunc } ;
    while(1) { $lasthash->{lastfunc}->(); } ;
}

test() ;
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Comment on Re^4: Disabling runtime warnings in dynamic scope? Download Code

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Re^5: Disabling runtime warnings in dynamic scope? by LanX (Saint) on Apr 26, 2018 at 13:13 UTC
I think two variables where confused here, `$^W` is dynamically scoped but can hold only one boolean state, not a variety of warning bits like `${^WARNING_BITS}` . From `perlvar` `● $WARNING ● $^W The current value of the warning switch, initially true if -w was used, false otherwise, but directly modifiable. See also warnings. Mnemonic: related to the -w switch. ● ${^WARNING_BITS} The current set of warning checks enabled by the use warnings pragma. It has the same scoping as the $^H and %^H variables. The exact values are considered internal to the warnings pragma and may change between versions of Perl.` `This variable was added in Perl v5.6.0.` I suppose that `${^WARNING_BITS}` * can be dynamically changed, but then only with great care (I wouldn't be surprised if implementation changed) The bits are supposed to be set by `use warnings` which is statically scoped, hence here are dragons! Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Wikisyntax for the Monastery} *) to answer my own suspicion, `${^WARNING_BITS}` are only set at compile-time and undef at run-time!	[reply] [d/l] [select]
Re^6: Disabling runtime warnings in dynamic scope? by LanX (Saint) on Apr 26, 2018 at 14:02 UTC
FWIW, like suspected, ${^WARNING_BITS} is a pure compile time effect, no dynamic scope possible. `use strict; use warnings; use Data::Dump qw/pp dd/; my ($before,$after); BEGIN { $before = ${^WARNING_BITS} } no warnings 'exiting'; BEGIN { $after = ${^WARNING_BITS} } my $diff = $before ^ $after; warn unpack ('B*',$diff); { use warnings; BEGIN { ${^WARNING_BITS} = $after }; # this only works at compile + time!!! sub test {last }; test(); }` [download] Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Wikisyntax for the Monastery}	[reply] [d/l]