#!/usr/bin/perl
-#
+#
# Regenerate (overwriting only if changed):
#
# lib/warnings.pm
-# pod/perllexwarn.pod
# warnings.h
#
# from information hardcoded into this script (the $tree hash), plus the
-# template for warnings.pm in the DATA section. Only part of
-# pod/perllexwarn.pod (the warnings category hierarchy) is generated,
-# the other parts remaining untouched.
+# template for warnings.pm in the DATA section.
#
# When changing the number of warnings, t/op/caller.t should change to
# correspond with the value of $BYTES in lib/warnings.pm
#
# This script is normally invoked from regen.pl.
-$VERSION = '1.02_05';
+$VERSION = '1.45';
BEGIN {
- require 'regen/regen_lib.pl';
+ require './regen/regen_lib.pl';
push @INC, './lib';
}
use strict ;
sub DEFAULT_OFF () { 2 }
my $tree = {
-
'all' => [ 5.008, {
- 'io' => [ 5.008, {
- 'pipe' => [ 5.008, DEFAULT_OFF],
- 'unopened' => [ 5.008, DEFAULT_OFF],
- 'closed' => [ 5.008, DEFAULT_OFF],
- 'newline' => [ 5.008, DEFAULT_OFF],
- 'exec' => [ 5.008, DEFAULT_OFF],
- 'layer' => [ 5.008, DEFAULT_OFF],
- 'syscalls' => [ 5.019, DEFAULT_OFF],
- }],
- 'syntax' => [ 5.008, {
- 'ambiguous' => [ 5.008, DEFAULT_OFF],
- 'semicolon' => [ 5.008, DEFAULT_OFF],
- 'precedence' => [ 5.008, DEFAULT_OFF],
- 'bareword' => [ 5.008, DEFAULT_OFF],
- 'reserved' => [ 5.008, DEFAULT_OFF],
- 'digit' => [ 5.008, DEFAULT_OFF],
- 'parenthesis' => [ 5.008, DEFAULT_OFF],
- 'printf' => [ 5.008, DEFAULT_OFF],
- 'prototype' => [ 5.008, DEFAULT_OFF],
- 'qw' => [ 5.008, DEFAULT_OFF],
+ 'io' => [ 5.008, {
+ 'pipe' => [ 5.008, DEFAULT_OFF],
+ 'unopened' => [ 5.008, DEFAULT_OFF],
+ 'closed' => [ 5.008, DEFAULT_OFF],
+ 'newline' => [ 5.008, DEFAULT_OFF],
+ 'exec' => [ 5.008, DEFAULT_OFF],
+ 'layer' => [ 5.008, DEFAULT_OFF],
+ 'syscalls' => [ 5.019, DEFAULT_OFF],
+ }],
+ 'syntax' => [ 5.008, {
+ 'ambiguous' => [ 5.008, DEFAULT_OFF],
+ 'semicolon' => [ 5.008, DEFAULT_OFF],
+ 'precedence' => [ 5.008, DEFAULT_OFF],
+ 'bareword' => [ 5.008, DEFAULT_OFF],
+ 'reserved' => [ 5.008, DEFAULT_OFF],
+ 'digit' => [ 5.008, DEFAULT_OFF],
+ 'parenthesis' => [ 5.008, DEFAULT_OFF],
+ 'printf' => [ 5.008, DEFAULT_OFF],
+ 'prototype' => [ 5.008, DEFAULT_OFF],
+ 'qw' => [ 5.008, DEFAULT_OFF],
'illegalproto' => [ 5.011, DEFAULT_OFF],
- }],
- 'severe' => [ 5.008, {
- 'inplace' => [ 5.008, DEFAULT_ON],
- 'internal' => [ 5.008, DEFAULT_OFF],
- 'debugging' => [ 5.008, DEFAULT_ON],
- 'malloc' => [ 5.008, DEFAULT_ON],
- }],
- 'deprecated' => [ 5.008, DEFAULT_ON],
- 'void' => [ 5.008, DEFAULT_OFF],
- 'recursion' => [ 5.008, DEFAULT_OFF],
- 'redefine' => [ 5.008, DEFAULT_OFF],
- 'numeric' => [ 5.008, DEFAULT_OFF],
- 'uninitialized' => [ 5.008, DEFAULT_OFF],
- 'once' => [ 5.008, DEFAULT_OFF],
- 'misc' => [ 5.008, DEFAULT_OFF],
- 'regexp' => [ 5.008, DEFAULT_OFF],
- 'glob' => [ 5.008, DEFAULT_ON],
- 'untie' => [ 5.008, DEFAULT_OFF],
- 'substr' => [ 5.008, DEFAULT_OFF],
- 'taint' => [ 5.008, DEFAULT_OFF],
- 'signal' => [ 5.008, DEFAULT_OFF],
- 'closure' => [ 5.008, DEFAULT_OFF],
- 'overflow' => [ 5.008, DEFAULT_OFF],
- 'portable' => [ 5.008, DEFAULT_OFF],
- 'utf8' => [ 5.008, {
+ }],
+ 'severe' => [ 5.008, {
+ 'inplace' => [ 5.008, DEFAULT_ON],
+ 'internal' => [ 5.008, DEFAULT_OFF],
+ 'debugging' => [ 5.008, DEFAULT_ON],
+ 'malloc' => [ 5.008, DEFAULT_ON],
+ }],
+ 'deprecated' => [ 5.008, DEFAULT_ON],
+ 'void' => [ 5.008, DEFAULT_OFF],
+ 'recursion' => [ 5.008, DEFAULT_OFF],
+ 'redefine' => [ 5.008, DEFAULT_OFF],
+ 'numeric' => [ 5.008, DEFAULT_OFF],
+ 'uninitialized' => [ 5.008, DEFAULT_OFF],
+ 'once' => [ 5.008, DEFAULT_OFF],
+ 'misc' => [ 5.008, DEFAULT_OFF],
+ 'regexp' => [ 5.008, DEFAULT_OFF],
+ 'glob' => [ 5.008, DEFAULT_ON],
+ 'untie' => [ 5.008, DEFAULT_OFF],
+ 'substr' => [ 5.008, DEFAULT_OFF],
+ 'taint' => [ 5.008, DEFAULT_OFF],
+ 'signal' => [ 5.008, DEFAULT_OFF],
+ 'closure' => [ 5.008, DEFAULT_OFF],
+ 'overflow' => [ 5.008, DEFAULT_OFF],
+ 'portable' => [ 5.008, DEFAULT_OFF],
+ 'utf8' => [ 5.008, {
'surrogate' => [ 5.013, DEFAULT_OFF],
'nonchar' => [ 5.013, DEFAULT_OFF],
'non_unicode' => [ 5.013, DEFAULT_OFF],
}],
- 'exiting' => [ 5.008, DEFAULT_OFF],
- 'pack' => [ 5.008, DEFAULT_OFF],
- 'unpack' => [ 5.008, DEFAULT_OFF],
- 'threads' => [ 5.008, DEFAULT_OFF],
- 'imprecision' => [ 5.011, DEFAULT_OFF],
- 'experimental' => [ 5.017, {
+ 'exiting' => [ 5.008, DEFAULT_OFF],
+ 'pack' => [ 5.008, DEFAULT_OFF],
+ 'unpack' => [ 5.008, DEFAULT_OFF],
+ 'threads' => [ 5.008, DEFAULT_OFF],
+ 'imprecision' => [ 5.011, DEFAULT_OFF],
+ 'experimental' => [ 5.017, {
'experimental::lexical_subs' =>
[ 5.017, DEFAULT_ON ],
'experimental::regex_sets' =>
[ 5.017, DEFAULT_ON ],
- 'experimental::lexical_topic' =>
- [ 5.017, DEFAULT_ON ],
'experimental::smartmatch' =>
[ 5.017, DEFAULT_ON ],
'experimental::postderef' =>
[ 5.019, DEFAULT_ON ],
- 'experimental::autoderef' =>
+ 'experimental::signatures' =>
[ 5.019, DEFAULT_ON ],
+ 'experimental::win32_perlio' =>
+ [ 5.021, DEFAULT_ON ],
+ 'experimental::refaliasing' =>
+ [ 5.021, DEFAULT_ON ],
+ 'experimental::re_strict' =>
+ [ 5.021, DEFAULT_ON ],
+ 'experimental::const_attr' =>
+ [ 5.021, DEFAULT_ON ],
+ 'experimental::bitwise' =>
+ [ 5.021, DEFAULT_ON ],
+ 'experimental::declared_refs' =>
+ [ 5.025, DEFAULT_ON ],
+ 'experimental::script_run' =>
+ [ 5.027, DEFAULT_ON ],
+ 'experimental::alpha_assertions' =>
+ [ 5.027, DEFAULT_ON ],
+ 'experimental::private_use' =>
+ [ 5.029, DEFAULT_ON ],
+ 'experimental::uniprop_wildcards' =>
+ [ 5.029, DEFAULT_ON ],
+ 'experimental::vlb' =>
+ [ 5.029, DEFAULT_ON ],
}],
- #'default' => [ 5.008, DEFAULT_ON ],
- }],
-} ;
+ 'missing' => [ 5.021, DEFAULT_OFF],
+ 'redundant' => [ 5.021, DEFAULT_OFF],
+ 'locale' => [ 5.021, DEFAULT_ON],
+ 'shadow' => [ 5.027, DEFAULT_OFF],
+
+ #'default' => [ 5.008, DEFAULT_ON ],
+}]};
my @def ;
my %list ;
my ($ver, $rest) = @{ $v } ;
push @{ $v_list{$ver} }, $k;
-
+
if (ref $rest)
{ valueWalk ($rest) }
push @{ $list{$k} }, $NameToValue{uc $k} ;
die "Value associated with key '$k' is not an ARRAY reference"
if !ref $v || ref $v ne 'ARRAY' ;
-
+
my ($ver, $rest) = @{ $v } ;
if (ref $rest)
{ push (@{ $list{$k} }, walk ($rest)) }
}
###########################################################################
-sub printTree
+sub warningsTree
{
my $tre = shift ;
my $prefix = shift ;
my $max = (sort {$a <=> $b} map { length $_ } keys %$tre)[-1] ;
my @keys = sort keys %$tre ;
+ my $rv = '';
+
while ($k = shift @keys) {
$v = $tre->{$k};
die "Value associated with key '$k' is not an ARRAY reference"
if !ref $v || ref $v ne 'ARRAY' ;
-
+
my $offset ;
if ($tre ne $tree) {
- print $prefix . "|\n" ;
- print $prefix . "+- $k" ;
+ $rv .= $prefix . "|\n" ;
+ $rv .= $prefix . "+- $k" ;
$offset = ' ' x ($max + 4) ;
}
else {
- print $prefix . "$k" ;
+ $rv .= $prefix . "$k" ;
$offset = ' ' x ($max + 1) ;
}
if (ref $rest)
{
my $bar = @keys ? "|" : " ";
- print " -" . "-" x ($max - length $k ) . "+\n" ;
- printTree ($rest, $prefix . $bar . $offset )
+ $rv .= " -" . "-" x ($max - length $k ) . "+\n" ;
+ $rv .= warningsTree ($rest, $prefix . $bar . $offset )
}
else
- { print "\n" }
+ { $rv .= "\n" }
}
+ return $rv;
}
###########################################################################
if (@ARGV && $ARGV[0] eq "tree")
{
- printTree($tree, " ") ;
+ print warningsTree($tree, " ") ;
exit ;
}
open_new($_, '>', { by => 'regen/warnings.pl' });
} 'warnings.h', 'lib/warnings.pm';
-print $warn <<'EOM';
+my ($index, $warn_size);
+
+{
+ # generate warnings.h
+
+ print $warn <<'EOM';
#define Off(x) ((x) / 8)
#define Bit(x) (1 << ((x) % 8))
#define G_WARN_ALL_MASK (G_WARN_ALL_ON|G_WARN_ALL_OFF)
#define pWARN_STD NULL
-#define pWARN_ALL (((STRLEN*)0)+1) /* use warnings 'all' */
-#define pWARN_NONE (((STRLEN*)0)+2) /* no warnings 'all' */
+#define pWARN_ALL (STRLEN *) &PL_WARN_ALL /* use warnings 'all' */
+#define pWARN_NONE (STRLEN *) &PL_WARN_NONE /* no warnings 'all' */
#define specialWARN(x) ((x) == pWARN_STD || (x) == pWARN_ALL || \
(x) == pWARN_NONE)
#define PERL_WARNHOOK_FATAL (&PL_sv_placeholder)
EOM
-my $offset = 0 ;
+ my $offset = 0 ;
-valueWalk ($tree) ;
-my $index = orderValues();
+ valueWalk ($tree) ;
+ $index = orderValues();
-die <<EOM if $index > 255 ;
+ die <<EOM if $index > 255 ;
Too many warnings categories -- max is 255
- rewrite packWARN* & unpackWARN* macros
+ rewrite packWARN* & unpackWARN* macros
EOM
-walk ($tree) ;
+ walk ($tree) ;
+ for (my $i = $index; $i & 3; $i++) {
+ push @{$list{all}}, $i;
+ }
+
+ $index *= 2 ;
+ $warn_size = int($index / 8) + ($index % 8 != 0) ;
+
+ my $k ;
+ my $last_ver = 0;
+ my @names;
+ foreach $k (sort { $a <=> $b } keys %ValueToName) {
+ my ($name, $version) = @{ $ValueToName{$k} };
+ print $warn "\n/* Warnings Categories added in Perl $version */\n\n"
+ if $last_ver != $version ;
+ $name =~ y/:/_/;
+ $name = "WARN_$name";
+ print $warn tab(6, "#define $name"), " $k\n" ;
+ push @names, $name;
+ $last_ver = $version ;
+ }
+ print $warn "\n\n/*\n" ;
+
+ print $warn map { "=for apidoc Amnh||$_\n" } @names;
+ print $warn "\n=cut\n*/\n\n" ;
+
+ print $warn tab(6, '#define WARNsize'), " $warn_size\n" ;
+ print $warn tab(6, '#define WARN_ALLstring'), ' "', ('\125' x $warn_size) , "\"\n" ;
+ print $warn tab(6, '#define WARN_NONEstring'), ' "', ('\0' x $warn_size) , "\"\n" ;
+
+ print $warn <<'EOM';
+
+#define isLEXWARN_on \
+ cBOOL(PL_curcop && PL_curcop->cop_warnings != pWARN_STD)
+#define isLEXWARN_off \
+ cBOOL(!PL_curcop || PL_curcop->cop_warnings == pWARN_STD)
+#define isWARN_ONCE (PL_dowarn & (G_WARN_ON|G_WARN_ONCE))
+#define isWARN_on(c,x) (IsSet((U8 *)(c + 1), 2*(x)))
+#define isWARNf_on(c,x) (IsSet((U8 *)(c + 1), 2*(x)+1))
-$index *= 2 ;
-my $warn_size = int($index / 8) + ($index % 8 != 0) ;
+#define DUP_WARNINGS(p) Perl_dup_warnings(aTHX_ p)
-my $k ;
-my $last_ver = 0;
-foreach $k (sort { $a <=> $b } keys %ValueToName) {
- my ($name, $version) = @{ $ValueToName{$k} };
- print $warn "\n/* Warnings Categories added in Perl $version */\n\n"
- if $last_ver != $version ;
- $name =~ y/:/_/;
- print $warn tab(5, "#define WARN_$name"), " $k\n" ;
- $last_ver = $version ;
-}
-print $warn "\n" ;
+/*
-print $warn tab(5, '#define WARNsize'), "$warn_size\n" ;
-#print WARN tab(5, '#define WARN_ALLstring'), '"', ('\377' x $warn_size) , "\"\n" ;
-print $warn tab(5, '#define WARN_ALLstring'), '"', ('\125' x $warn_size) , "\"\n" ;
-print $warn tab(5, '#define WARN_NONEstring'), '"', ('\0' x $warn_size) , "\"\n" ;
+=head1 Warning and Dieing
-print $warn <<'EOM';
+In all these calls, the C<U32 wI<n>> parameters are warning category
+constants. You can see the ones currently available in
+L<warnings/Category Hierarchy>, just capitalize all letters in the names
+and prefix them by C<WARN_>. So, for example, the category C<void> used in a
+perl program becomes C<WARN_VOID> when used in XS code and passed to one of
+the calls below.
-#define isLEXWARN_on (PL_curcop->cop_warnings != pWARN_STD)
-#define isLEXWARN_off (PL_curcop->cop_warnings == pWARN_STD)
-#define isWARN_ONCE (PL_dowarn & (G_WARN_ON|G_WARN_ONCE))
-#define isWARN_on(c,x) (IsSet((U8 *)(c + 1), 2*(x)))
-#define isWARNf_on(c,x) (IsSet((U8 *)(c + 1), 2*(x)+1))
+=for apidoc Am|bool|ckWARN|U32 w
+
+Returns a boolean as to whether or not warnings are enabled for the warning
+category C<w>. If the category is by default enabled even if not within the
+scope of S<C<use warnings>>, instead use the L</ckWARN_d> macro.
+
+=for apidoc Am|bool|ckWARN_d|U32 w
+
+Like C<L</ckWARN>>, but for use if and only if the warning category is by
+default enabled even if not within the scope of S<C<use warnings>>.
+
+=for apidoc Am|bool|ckWARN2|U32 w1|U32 w2
+
+Like C<L</ckWARN>>, but takes two warnings categories as input, and returns
+TRUE if either is enabled. If either category is by default enabled even if
+not within the scope of S<C<use warnings>>, instead use the L</ckWARN2_d>
+macro. The categories must be completely independent, one may not be
+subclassed from the other.
+
+=for apidoc Am|bool|ckWARN2_d|U32 w1|U32 w2
+
+Like C<L</ckWARN2>>, but for use if and only if either warning category is by
+default enabled even if not within the scope of S<C<use warnings>>.
+
+=for apidoc Am|bool|ckWARN3|U32 w1|U32 w2|U32 w3
+
+Like C<L</ckWARN2>>, but takes three warnings categories as input, and returns
+TRUE if any is enabled. If any of the categories is by default enabled even
+if not within the scope of S<C<use warnings>>, instead use the L</ckWARN3_d>
+macro. The categories must be completely independent, one may not be
+subclassed from any other.
+
+=for apidoc Am|bool|ckWARN3_d|U32 w1|U32 w2|U32 w3
+
+Like C<L</ckWARN3>>, but for use if and only if any of the warning categories
+is by default enabled even if not within the scope of S<C<use warnings>>.
+
+=for apidoc Am|bool|ckWARN4|U32 w1|U32 w2|U32 w3|U32 w4
-#define DUP_WARNINGS(p) \
- (specialWARN(p) ? (STRLEN*)(p) \
- : (STRLEN*)CopyD(p, PerlMemShared_malloc(sizeof(*p)+*p), sizeof(*p)+*p, \
- char))
+Like C<L</ckWARN3>>, but takes four warnings categories as input, and returns
+TRUE if any is enabled. If any of the categories is by default enabled even
+if not within the scope of S<C<use warnings>>, instead use the L</ckWARN4_d>
+macro. The categories must be completely independent, one may not be
+subclassed from any other.
+
+=for apidoc Am|bool|ckWARN4_d|U32 w1|U32 w2|U32 w3|U32 w4
+
+Like C<L</ckWARN4>>, but for use if and only if any of the warning categories
+is by default enabled even if not within the scope of S<C<use warnings>>.
+
+=cut
+
+*/
#define ckWARN(w) Perl_ckwarn(aTHX_ packWARN(w))
#define unpackWARN4(x) (((x) >>24) & 0xFF)
#define ckDEAD(x) \
- ( ! specialWARN(PL_curcop->cop_warnings) && \
- ( isWARNf_on(PL_curcop->cop_warnings, WARN_ALL) || \
- isWARNf_on(PL_curcop->cop_warnings, unpackWARN1(x)) || \
- isWARNf_on(PL_curcop->cop_warnings, unpackWARN2(x)) || \
- isWARNf_on(PL_curcop->cop_warnings, unpackWARN3(x)) || \
- isWARNf_on(PL_curcop->cop_warnings, unpackWARN4(x))))
+ (PL_curcop && \
+ !specialWARN(PL_curcop->cop_warnings) && \
+ (isWARNf_on(PL_curcop->cop_warnings, unpackWARN1(x)) || \
+ (unpackWARN2(x) && \
+ (isWARNf_on(PL_curcop->cop_warnings, unpackWARN2(x)) || \
+ (unpackWARN3(x) && \
+ (isWARNf_on(PL_curcop->cop_warnings, unpackWARN3(x)) || \
+ (unpackWARN4(x) && \
+ isWARNf_on(PL_curcop->cop_warnings, unpackWARN4(x)))))))))
/* end of file warnings.h */
EOM
-read_only_bottom_close_and_rename($warn);
+ read_only_bottom_close_and_rename($warn);
+}
+
+while (<DATA>) {
+ last if /^VERSION$/ ;
+ print $pm $_ ;
+}
+
+print $pm qq(our \$VERSION = "$::VERSION";\n);
while (<DATA>) {
last if /^KEYWORDS$/ ;
print $pm $_ ;
}
-$last_ver = 0;
-print $pm "our %Offsets = (\n" ;
+my $last_ver = 0;
+print $pm "our %Offsets = (" ;
foreach my $k (sort { $a <=> $b } keys %ValueToName) {
my ($name, $version) = @{ $ValueToName{$k} };
$name = lc $name;
$k *= 2 ;
if ( $last_ver != $version ) {
print $pm "\n";
- print $pm tab(4, " # Warnings Categories added in Perl $version");
- print $pm "\n\n";
+ print $pm tab(6, " # Warnings Categories added in Perl $version");
+ print $pm "\n";
}
- print $pm tab(4, " '$name'"), "=> $k,\n" ;
+ print $pm tab(6, " '$name'"), "=> $k,\n" ;
$last_ver = $version;
}
-print $pm " );\n\n" ;
+print $pm ");\n\n" ;
print $pm "our %Bits = (\n" ;
-foreach $k (sort keys %list) {
+foreach my $k (sort keys %list) {
my $v = $list{$k} ;
my @list = sort { $a <=> $b } @$v ;
- print $pm tab(4, " '$k'"), '=> "',
+ print $pm tab(6, " '$k'"), '=> "',
mkHex($warn_size, map $_ * 2 , @list),
'", # [', mkRange(@list), "]\n" ;
}
-print $pm " );\n\n" ;
+print $pm ");\n\n" ;
print $pm "our %DeadBits = (\n" ;
-foreach $k (sort keys %list) {
+foreach my $k (sort keys %list) {
my $v = $list{$k} ;
my @list = sort { $a <=> $b } @$v ;
- print $pm tab(4, " '$k'"), '=> "',
+ print $pm tab(6, " '$k'"), '=> "',
mkHex($warn_size, map $_ * 2 + 1 , @list),
'", # [', mkRange(@list), "]\n" ;
}
-print $pm " );\n\n" ;
-print $pm '$NONE = "', ('\0' x $warn_size) , "\";\n" ;
-print $pm '$DEFAULT = "', mkHex($warn_size, map $_ * 2, @def),
- '", # [', mkRange(@def), "]\n" ;
-print $pm '$LAST_BIT = ' . "$index ;\n" ;
-print $pm '$BYTES = ' . "$warn_size ;\n" ;
+print $pm ");\n\n" ;
+print $pm "# These are used by various things, including our own tests\n";
+print $pm tab(6, 'our $NONE'), '= "', ('\0' x $warn_size) , "\";\n" ;
+print $pm tab(6, 'our $DEFAULT'), '= "', mkHex($warn_size, map $_ * 2, @def),
+ '", # [', mkRange(sort { $a <=> $b } @def), "]\n" ;
+print $pm tab(6, 'our $LAST_BIT'), '= ' . "$index ;\n" ;
+print $pm tab(6, 'our $BYTES'), '= ' . "$warn_size ;\n" ;
while (<DATA>) {
+ if ($_ eq "=for warnings.pl tree-goes-here\n") {
+ print $pm warningsTree($tree, " ");
+ next;
+ }
print $pm $_ ;
}
read_only_bottom_close_and_rename($pm);
-my $lexwarn = open_new 'pod/perllexwarn.pod', '>';
-open my $oldlexwarn, "pod/perllexwarn.pod"
- or die "$0 cannot open pod/perllexwarn.pod for reading: $!";
-select +(select($lexwarn), do {
- while(<$oldlexwarn>) {
- print;
- last if /=for warnings.pl begin/;
- }
- print "\n";
- printTree($tree, " ") ;
- print "\n";
- while(<$oldlexwarn>) {
- last if /=for warnings.pl end/;
- }
- do { print } while <$oldlexwarn>;
-})[0];
-
-close_and_rename($lexwarn);
-
__END__
package warnings;
-our $VERSION = '1.22';
+VERSION
# Verify that we're called correctly so that warnings will work.
+# Can't use Carp, since Carp uses us!
+# String regexps because constant folding = smaller optree = less memory vs regexp literal
# see also strict.pm.
-unless ( __FILE__ =~ /(^|[\/\\])\Q${\__PACKAGE__}\E\.pmc?$/ ) {
- my (undef, $f, $l) = caller;
- die("Incorrect use of pragma '${\__PACKAGE__}' at $f line $l.\n");
-}
-
-=head1 NAME
-
-warnings - Perl pragma to control optional warnings
-
-=head1 SYNOPSIS
-
- use warnings;
- no warnings;
-
- use warnings "all";
- no warnings "all";
-
- use warnings::register;
- if (warnings::enabled()) {
- warnings::warn("some warning");
- }
-
- if (warnings::enabled("void")) {
- warnings::warn("void", "some warning");
- }
-
- if (warnings::enabled($object)) {
- warnings::warn($object, "some warning");
- }
-
- warnings::warnif("some warning");
- warnings::warnif("void", "some warning");
- warnings::warnif($object, "some warning");
-
-=head1 DESCRIPTION
-
-The C<warnings> pragma is a replacement for the command line flag C<-w>,
-but the pragma is limited to the enclosing block, while the flag is global.
-See L<perllexwarn> for more information and the list of built-in warning
-categories.
-
-If no import list is supplied, all possible warnings are either enabled
-or disabled.
-
-A number of functions are provided to assist module authors.
-
-=over 4
-
-=item use warnings::register
-
-Creates a new warnings category with the same name as the package where
-the call to the pragma is used.
-
-=item warnings::enabled()
-
-Use the warnings category with the same name as the current package.
-
-Return TRUE if that warnings category is enabled in the calling module.
-Otherwise returns FALSE.
-
-=item warnings::enabled($category)
-
-Return TRUE if the warnings category, C<$category>, is enabled in the
-calling module.
-Otherwise returns FALSE.
-
-=item warnings::enabled($object)
-
-Use the name of the class for the object reference, C<$object>, as the
-warnings category.
-
-Return TRUE if that warnings category is enabled in the first scope
-where the object is used.
-Otherwise returns FALSE.
-
-=item warnings::fatal_enabled()
-
-Return TRUE if the warnings category with the same name as the current
-package has been set to FATAL in the calling module.
-Otherwise returns FALSE.
-
-=item warnings::fatal_enabled($category)
-
-Return TRUE if the warnings category C<$category> has been set to FATAL in
-the calling module.
-Otherwise returns FALSE.
-
-=item warnings::fatal_enabled($object)
-
-Use the name of the class for the object reference, C<$object>, as the
-warnings category.
-
-Return TRUE if that warnings category has been set to FATAL in the first
-scope where the object is used.
-Otherwise returns FALSE.
-
-=item warnings::warn($message)
-
-Print C<$message> to STDERR.
-
-Use the warnings category with the same name as the current package.
-
-If that warnings category has been set to "FATAL" in the calling module
-then die. Otherwise return.
-
-=item warnings::warn($category, $message)
-
-Print C<$message> to STDERR.
-
-If the warnings category, C<$category>, has been set to "FATAL" in the
-calling module then die. Otherwise return.
-
-=item warnings::warn($object, $message)
-
-Print C<$message> to STDERR.
-
-Use the name of the class for the object reference, C<$object>, as the
-warnings category.
-
-If that warnings category has been set to "FATAL" in the scope where C<$object>
-is first used then die. Otherwise return.
-
-
-=item warnings::warnif($message)
-
-Equivalent to:
-
- if (warnings::enabled())
- { warnings::warn($message) }
-
-=item warnings::warnif($category, $message)
-
-Equivalent to:
-
- if (warnings::enabled($category))
- { warnings::warn($category, $message) }
-
-=item warnings::warnif($object, $message)
-
-Equivalent to:
-
- if (warnings::enabled($object))
- { warnings::warn($object, $message) }
-
-=item warnings::register_categories(@names)
-
-This registers warning categories for the given names and is primarily for
-use by the warnings::register pragma, for which see L<perllexwarn>.
-
-=back
-
-See L<perlmodlib/Pragmatic Modules> and L<perllexwarn>.
-
-=cut
+die sprintf "Incorrect use of pragma '%s' at %s line %d.\n", __PACKAGE__, +(caller)[1,2]
+ if __FILE__ !~ ( '(?x) \b '.__PACKAGE__.' \.pmc? \z' )
+ && __FILE__ =~ ( '(?x) \b (?i:'.__PACKAGE__.') \.pmc? \z' );
KEYWORDS
-$All = "" ; vec($All, $Offsets{'all'}, 2) = 3 ;
-
sub Croaker
{
require Carp; # this initializes %CarpInternal
Carp::croak(@_);
}
+sub _expand_bits {
+ my $bits = shift;
+ my $want_len = ($LAST_BIT + 7) >> 3;
+ my $len = length($bits);
+ if ($len != $want_len) {
+ if ($bits eq "") {
+ $bits = "\x00" x $want_len;
+ } elsif ($len > $want_len) {
+ substr $bits, $want_len, $len-$want_len, "";
+ } else {
+ my $a = vec($bits, $Offsets{all} >> 1, 2);
+ $a |= $a << 2;
+ $a |= $a << 4;
+ $bits .= chr($a) x ($want_len - $len);
+ }
+ }
+ return $bits;
+}
+
sub _bits {
my $mask = shift ;
my $catmask ;
my $fatal = 0 ;
my $no_fatal = 0 ;
+ $mask = _expand_bits($mask);
foreach my $word ( @_ ) {
if ($word eq 'FATAL') {
$fatal = 1;
elsif ($catmask = $Bits{$word}) {
$mask |= $catmask ;
$mask |= $DeadBits{$word} if $fatal ;
- $mask &= ~($DeadBits{$word}|$All) if $no_fatal ;
+ $mask = ~(~$mask | $DeadBits{$word}) if $no_fatal ;
}
else
- { Croaker("Unknown warnings category '$word'")}
+ { Croaker("Unknown warnings category '$word'")}
}
return $mask ;
{
# called from B::Deparse.pm
push @_, 'all' unless @_ ;
- return _bits(undef, @_) ;
+ return _bits("", @_) ;
}
-sub import
+sub import
{
shift;
my $mask = ${^WARNING_BITS} // ($^W ? $Bits{all} : $DEFAULT) ;
- if (vec($mask, $Offsets{'all'}, 1)) {
- $mask |= $Bits{'all'} ;
- $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
- }
+ # append 'all' when implied (empty import list or after a lone
+ # "FATAL" or "NONFATAL")
+ push @_, 'all'
+ if !@_ || (@_==1 && ($_[0] eq 'FATAL' || $_[0] eq 'NONFATAL'));
- # append 'all' when implied (after a lone "FATAL" or "NONFATAL")
- push @_, 'all' if @_==1 && ( $_[0] eq 'FATAL' || $_[0] eq 'NONFATAL' );
-
- # Empty @_ is equivalent to @_ = 'all' ;
- ${^WARNING_BITS} = @_ ? _bits($mask, @_) : $mask | $Bits{all} ;
+ ${^WARNING_BITS} = _bits($mask, @_);
}
-sub unimport
+sub unimport
{
shift;
my $catmask ;
my $mask = ${^WARNING_BITS} // ($^W ? $Bits{all} : $DEFAULT) ;
- if (vec($mask, $Offsets{'all'}, 1)) {
- $mask |= $Bits{'all'} ;
- $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
- }
-
# append 'all' when implied (empty import list or after a lone "FATAL")
push @_, 'all' if !@_ || @_==1 && $_[0] eq 'FATAL';
+ $mask = _expand_bits($mask);
foreach my $word ( @_ ) {
if ($word eq 'FATAL') {
- next;
+ next;
}
elsif ($catmask = $Bits{$word}) {
- $mask &= ~($catmask | $DeadBits{$word} | $All);
+ $mask = ~(~$mask | $catmask | $DeadBits{$word});
}
else
- { Croaker("Unknown warnings category '$word'")}
+ { Croaker("Unknown warnings category '$word'")}
}
${^WARNING_BITS} = $mask ;
my %builtin_type; @builtin_type{qw(SCALAR ARRAY HASH CODE REF GLOB LVALUE Regexp)} = ();
+sub LEVEL () { 8 };
sub MESSAGE () { 4 };
sub FATAL () { 2 };
sub NORMAL () { 1 };
my $isobj = 0 ;
my $wanted = shift;
my $has_message = $wanted & MESSAGE;
-
- unless (@_ == 1 || @_ == ($has_message ? 2 : 0)) {
+ my $has_level = $wanted & LEVEL ;
+
+ if ($has_level) {
+ if (@_ != ($has_message ? 3 : 2)) {
+ my $sub = (caller 1)[3];
+ my $syntax = $has_message
+ ? "category, level, 'message'"
+ : 'category, level';
+ Croaker("Usage: $sub($syntax)");
+ }
+ }
+ elsif (not @_ == 1 || @_ == ($has_message ? 2 : 0)) {
my $sub = (caller 1)[3];
my $syntax = $has_message ? "[category,] 'message'" : '[category]';
Croaker("Usage: $sub($syntax)");
my $message = pop if $has_message;
if (@_) {
- # check the category supplied.
- $category = shift ;
- if (my $type = ref $category) {
- Croaker("not an object")
- if exists $builtin_type{$type};
+ # check the category supplied.
+ $category = shift ;
+ if (my $type = ref $category) {
+ Croaker("not an object")
+ if exists $builtin_type{$type};
$category = $type;
- $isobj = 1 ;
- }
- $offset = $Offsets{$category};
- Croaker("Unknown warnings category '$category'")
+ $isobj = 1 ;
+ }
+ $offset = $Offsets{$category};
+ Croaker("Unknown warnings category '$category'")
unless defined $offset;
}
else {
- $category = (caller(1))[0] ;
- $offset = $Offsets{$category};
- Croaker("package '$category' not registered for warnings")
+ $category = (caller(1))[0] ;
+ $offset = $Offsets{$category};
+ Croaker("package '$category' not registered for warnings")
unless defined $offset ;
}
my $i;
if ($isobj) {
- my $pkg;
- $i = 2;
- while (do { { package DB; $pkg = (caller($i++))[0] } } ) {
- last unless @DB::args && $DB::args[0] =~ /^$category=/ ;
- }
+ my $pkg;
+ $i = 2;
+ while (do { { package DB; $pkg = (caller($i++))[0] } } ) {
+ last unless @DB::args && $DB::args[0] =~ /^$category=/ ;
+ }
$i -= 2 ;
}
+ elsif ($has_level) {
+ $i = 2 + shift;
+ }
else {
- $i = _error_loc(); # see where Carp will allocate the error
+ $i = _error_loc(); # see where Carp will allocate the error
}
# Default to 0 if caller returns nothing. Default to $DEFAULT if it
my(@callers_bitmask) = (caller($i))[9] ;
my $callers_bitmask =
@callers_bitmask ? $callers_bitmask[0] // $DEFAULT : 0 ;
+ length($callers_bitmask) > ($offset >> 3) or $offset = $Offsets{all};
my @results;
foreach my $type (FATAL, NORMAL) {
next unless $wanted & $type;
- push @results, (vec($callers_bitmask, $offset + $type - 1, 1) ||
- vec($callers_bitmask, $Offsets{'all'} + $type - 1, 1));
+ push @results, vec($callers_bitmask, $offset + $type - 1, 1);
}
# &enabled and &fatal_enabled
return $results[0] unless $has_message;
# &warnif, and the category is neither enabled as warning nor as fatal
- return if $wanted == (NORMAL | FATAL | MESSAGE)
+ return if ($wanted & (NORMAL | FATAL | MESSAGE))
+ == (NORMAL | FATAL | MESSAGE)
&& !($results[0] || $results[1]);
+ # If we have an explicit level, bypass Carp.
+ if ($has_level and @callers_bitmask) {
+ # logic copied from util.c:mess_sv
+ my $stuff = " at " . join " line ", (caller $i)[1,2];
+ $stuff .= sprintf ", <%s> %s %d",
+ *${^LAST_FH}{NAME},
+ ($/ eq "\n" ? "line" : "chunk"), $.
+ if $. && ${^LAST_FH};
+ die "$message$stuff.\n" if $results[0];
+ return warn "$message$stuff.\n";
+ }
+
require Carp;
Carp::croak($message) if $results[0];
# will always get here for &warn. will only get here for &warnif if the
for my $name (@names) {
if (! defined $Bits{$name}) {
- $Bits{$name} = _mkMask($LAST_BIT);
- vec($Bits{'all'}, $LAST_BIT, 1) = 1;
- $Offsets{$name} = $LAST_BIT ++;
- foreach my $k (keys %Bits) {
- vec($Bits{$k}, $LAST_BIT, 1) = 0;
+ $Offsets{$name} = $LAST_BIT;
+ $Bits{$name} = _mkMask($LAST_BIT++);
+ $DeadBits{$name} = _mkMask($LAST_BIT++);
+ if (length($Bits{$name}) > length($Bits{all})) {
+ $Bits{all} .= "\x55";
+ $DeadBits{all} .= "\xaa";
}
- $DeadBits{$name} = _mkMask($LAST_BIT);
- vec($DeadBits{'all'}, $LAST_BIT++, 1) = 1;
}
}
}
return __chk(NORMAL | FATAL | MESSAGE, @_);
}
+sub enabled_at_level
+{
+ return __chk(NORMAL | LEVEL, @_);
+}
+
+sub fatal_enabled_at_level
+{
+ return __chk(FATAL | LEVEL, @_);
+}
+
+sub warn_at_level
+{
+ return __chk(FATAL | MESSAGE | LEVEL, @_);
+}
+
+sub warnif_at_level
+{
+ return __chk(NORMAL | FATAL | MESSAGE | LEVEL, @_);
+}
+
# These are not part of any public interface, so we can delete them to save
# space.
-delete @warnings::{qw(NORMAL FATAL MESSAGE)};
+delete @warnings::{qw(NORMAL FATAL MESSAGE LEVEL)};
1;
+__END__
+
+=head1 NAME
+
+warnings - Perl pragma to control optional warnings
+
+=head1 SYNOPSIS
+
+ use warnings;
+ no warnings;
+
+ use warnings "all";
+ no warnings "all";
+
+ use warnings::register;
+ if (warnings::enabled()) {
+ warnings::warn("some warning");
+ }
+
+ if (warnings::enabled("void")) {
+ warnings::warn("void", "some warning");
+ }
+
+ if (warnings::enabled($object)) {
+ warnings::warn($object, "some warning");
+ }
+
+ warnings::warnif("some warning");
+ warnings::warnif("void", "some warning");
+ warnings::warnif($object, "some warning");
+
+=head1 DESCRIPTION
+
+The C<warnings> pragma gives control over which warnings are enabled in
+which parts of a Perl program. It's a more flexible alternative for
+both the command line flag B<-w> and the equivalent Perl variable,
+C<$^W>.
+
+This pragma works just like the C<strict> pragma.
+This means that the scope of the warning pragma is limited to the
+enclosing block. It also means that the pragma setting will not
+leak across files (via C<use>, C<require> or C<do>). This allows
+authors to independently define the degree of warning checks that will
+be applied to their module.
+
+By default, optional warnings are disabled, so any legacy code that
+doesn't attempt to control the warnings will work unchanged.
+
+All warnings are enabled in a block by either of these:
+
+ use warnings;
+ use warnings 'all';
+
+Similarly all warnings are disabled in a block by either of these:
+
+ no warnings;
+ no warnings 'all';
+
+For example, consider the code below:
+
+ use warnings;
+ my @a;
+ {
+ no warnings;
+ my $b = @a[0];
+ }
+ my $c = @a[0];
+
+The code in the enclosing block has warnings enabled, but the inner
+block has them disabled. In this case that means the assignment to the
+scalar C<$c> will trip the C<"Scalar value @a[0] better written as $a[0]">
+warning, but the assignment to the scalar C<$b> will not.
+
+=head2 Default Warnings and Optional Warnings
+
+Before the introduction of lexical warnings, Perl had two classes of
+warnings: mandatory and optional.
+
+As its name suggests, if your code tripped a mandatory warning, you
+would get a warning whether you wanted it or not.
+For example, the code below would always produce an C<"isn't numeric">
+warning about the "2:".
+
+ my $a = "2:" + 3;
+
+With the introduction of lexical warnings, mandatory warnings now become
+I<default> warnings. The difference is that although the previously
+mandatory warnings are still enabled by default, they can then be
+subsequently enabled or disabled with the lexical warning pragma. For
+example, in the code below, an C<"isn't numeric"> warning will only
+be reported for the C<$a> variable.
+
+ my $a = "2:" + 3;
+ no warnings;
+ my $b = "2:" + 3;
+
+Note that neither the B<-w> flag or the C<$^W> can be used to
+disable/enable default warnings. They are still mandatory in this case.
+
+=head2 What's wrong with B<-w> and C<$^W>
+
+Although very useful, the big problem with using B<-w> on the command
+line to enable warnings is that it is all or nothing. Take the typical
+scenario when you are writing a Perl program. Parts of the code you
+will write yourself, but it's very likely that you will make use of
+pre-written Perl modules. If you use the B<-w> flag in this case, you
+end up enabling warnings in pieces of code that you haven't written.
+
+Similarly, using C<$^W> to either disable or enable blocks of code is
+fundamentally flawed. For a start, say you want to disable warnings in
+a block of code. You might expect this to be enough to do the trick:
+
+ {
+ local ($^W) = 0;
+ my $a =+ 2;
+ my $b; chop $b;
+ }
+
+When this code is run with the B<-w> flag, a warning will be produced
+for the C<$a> line: C<"Reversed += operator">.
+
+The problem is that Perl has both compile-time and run-time warnings. To
+disable compile-time warnings you need to rewrite the code like this:
+
+ {
+ BEGIN { $^W = 0 }
+ my $a =+ 2;
+ my $b; chop $b;
+ }
+
+The other big problem with C<$^W> is the way you can inadvertently
+change the warning setting in unexpected places in your code. For example,
+when the code below is run (without the B<-w> flag), the second call
+to C<doit> will trip a C<"Use of uninitialized value"> warning, whereas
+the first will not.
+
+ sub doit
+ {
+ my $b; chop $b;
+ }
+
+ doit();
+
+ {
+ local ($^W) = 1;
+ doit()
+ }
+
+This is a side-effect of C<$^W> being dynamically scoped.
+
+Lexical warnings get around these limitations by allowing finer control
+over where warnings can or can't be tripped.
+
+=head2 Controlling Warnings from the Command Line
+
+There are three Command Line flags that can be used to control when
+warnings are (or aren't) produced:
+
+=over 5
+
+=item B<-w>
+X<-w>
+
+This is the existing flag. If the lexical warnings pragma is B<not>
+used in any of you code, or any of the modules that you use, this flag
+will enable warnings everywhere. See L</Backward Compatibility> for
+details of how this flag interacts with lexical warnings.
+
+=item B<-W>
+X<-W>
+
+If the B<-W> flag is used on the command line, it will enable all warnings
+throughout the program regardless of whether warnings were disabled
+locally using C<no warnings> or C<$^W =0>.
+This includes all files that get
+included via C<use>, C<require> or C<do>.
+Think of it as the Perl equivalent of the "lint" command.
+
+=item B<-X>
+X<-X>
+
+Does the exact opposite to the B<-W> flag, i.e. it disables all warnings.
+
+=back
+
+=head2 Backward Compatibility
+
+If you are used to working with a version of Perl prior to the
+introduction of lexically scoped warnings, or have code that uses both
+lexical warnings and C<$^W>, this section will describe how they interact.
+
+How Lexical Warnings interact with B<-w>/C<$^W>:
+
+=over 5
+
+=item 1.
+
+If none of the three command line flags (B<-w>, B<-W> or B<-X>) that
+control warnings is used and neither C<$^W> nor the C<warnings> pragma
+are used, then default warnings will be enabled and optional warnings
+disabled.
+This means that legacy code that doesn't attempt to control the warnings
+will work unchanged.
+
+=item 2.
+
+The B<-w> flag just sets the global C<$^W> variable as in 5.005. This
+means that any legacy code that currently relies on manipulating C<$^W>
+to control warning behavior will still work as is.
+
+=item 3.
+
+Apart from now being a boolean, the C<$^W> variable operates in exactly
+the same horrible uncontrolled global way, except that it cannot
+disable/enable default warnings.
+
+=item 4.
+
+If a piece of code is under the control of the C<warnings> pragma,
+both the C<$^W> variable and the B<-w> flag will be ignored for the
+scope of the lexical warning.
+
+=item 5.
+
+The only way to override a lexical warnings setting is with the B<-W>
+or B<-X> command line flags.
+
+=back
+
+The combined effect of 3 & 4 is that it will allow code which uses
+the C<warnings> pragma to control the warning behavior of $^W-type
+code (using a C<local $^W=0>) if it really wants to, but not vice-versa.
+
+=head2 Category Hierarchy
+X<warning, categories>
+
+A hierarchy of "categories" have been defined to allow groups of warnings
+to be enabled/disabled in isolation.
+
+The current hierarchy is:
+
+=for warnings.pl tree-goes-here
+
+Just like the "strict" pragma any of these categories can be combined
+
+ use warnings qw(void redefine);
+ no warnings qw(io syntax untie);
+
+Also like the "strict" pragma, if there is more than one instance of the
+C<warnings> pragma in a given scope the cumulative effect is additive.
+
+ use warnings qw(void); # only "void" warnings enabled
+ ...
+ use warnings qw(io); # only "void" & "io" warnings enabled
+ ...
+ no warnings qw(void); # only "io" warnings enabled
+
+To determine which category a specific warning has been assigned to see
+L<perldiag>.
+
+Note: Before Perl 5.8.0, the lexical warnings category "deprecated" was a
+sub-category of the "syntax" category. It is now a top-level category
+in its own right.
+
+Note: Before 5.21.0, the "missing" lexical warnings category was
+internally defined to be the same as the "uninitialized" category. It
+is now a top-level category in its own right.
+
+=head2 Fatal Warnings
+X<warning, fatal>
+
+The presence of the word "FATAL" in the category list will escalate
+warnings in those categories into fatal errors in that lexical scope.
+
+B<NOTE:> FATAL warnings should be used with care, particularly
+C<< FATAL => 'all' >>.
+
+Libraries using L<warnings::warn|/FUNCTIONS> for custom warning categories
+generally don't expect L<warnings::warn|/FUNCTIONS> to be fatal and can wind up
+in an unexpected state as a result. For XS modules issuing categorized
+warnings, such unanticipated exceptions could also expose memory leak bugs.
+
+Moreover, the Perl interpreter itself has had serious bugs involving
+fatalized warnings. For a summary of resolved and unresolved problems as
+of January 2015, please see
+L<this perl5-porters post|http://www.nntp.perl.org/group/perl.perl5.porters/2015/01/msg225235.html>.
+
+While some developers find fatalizing some warnings to be a useful
+defensive programming technique, using C<< FATAL => 'all' >> to fatalize
+all possible warning categories -- including custom ones -- is particularly
+risky. Therefore, the use of C<< FATAL => 'all' >> is
+L<discouraged|perlpolicy/discouraged>.
+
+The L<strictures|strictures/VERSION-2> module on CPAN offers one example of
+a warnings subset that the module's authors believe is relatively safe to
+fatalize.
+
+B<NOTE:> users of FATAL warnings, especially those using
+C<< FATAL => 'all' >>, should be fully aware that they are risking future
+portability of their programs by doing so. Perl makes absolutely no
+commitments to not introduce new warnings or warnings categories in the
+future; indeed, we explicitly reserve the right to do so. Code that may
+not warn now may warn in a future release of Perl if the Perl5 development
+team deems it in the best interests of the community to do so. Should code
+using FATAL warnings break due to the introduction of a new warning we will
+NOT consider it an incompatible change. Users of FATAL warnings should
+take special caution during upgrades to check to see if their code triggers
+any new warnings and should pay particular attention to the fine print of
+the documentation of the features they use to ensure they do not exploit
+features that are documented as risky, deprecated, or unspecified, or where
+the documentation says "so don't do that", or anything with the same sense
+and spirit. Use of such features in combination with FATAL warnings is
+ENTIRELY AT THE USER'S RISK.
+
+The following documentation describes how to use FATAL warnings but the
+perl5 porters strongly recommend that you understand the risks before doing
+so, especially for library code intended for use by others, as there is no
+way for downstream users to change the choice of fatal categories.
+
+In the code below, the use of C<time>, C<length>
+and C<join> can all produce a C<"Useless use of xxx in void context">
+warning.
+
+ use warnings;
+
+ time;
+
+ {
+ use warnings FATAL => qw(void);
+ length "abc";
+ }
+
+ join "", 1,2,3;
+
+ print "done\n";
+
+When run it produces this output
+
+ Useless use of time in void context at fatal line 3.
+ Useless use of length in void context at fatal line 7.
+
+The scope where C<length> is used has escalated the C<void> warnings
+category into a fatal error, so the program terminates immediately when it
+encounters the warning.
+
+To explicitly turn off a "FATAL" warning you just disable the warning
+it is associated with. So, for example, to disable the "void" warning
+in the example above, either of these will do the trick:
+
+ no warnings qw(void);
+ no warnings FATAL => qw(void);
+
+If you want to downgrade a warning that has been escalated into a fatal
+error back to a normal warning, you can use the "NONFATAL" keyword. For
+example, the code below will promote all warnings into fatal errors,
+except for those in the "syntax" category.
+
+ use warnings FATAL => 'all', NONFATAL => 'syntax';
+
+As of Perl 5.20, instead of C<< use warnings FATAL => 'all'; >> you can
+use:
+
+ use v5.20; # Perl 5.20 or greater is required for the following
+ use warnings 'FATAL'; # short form of "use warnings FATAL => 'all';"
+
+If you want your program to be compatible with versions of Perl before
+5.20, you must use C<< use warnings FATAL => 'all'; >> instead. (In
+previous versions of Perl, the behavior of the statements
+C<< use warnings 'FATAL'; >>, C<< use warnings 'NONFATAL'; >> and
+C<< no warnings 'FATAL'; >> was unspecified; they did not behave as if
+they included the C<< => 'all' >> portion. As of 5.20, they do.)
+
+=head2 Reporting Warnings from a Module
+X<warning, reporting> X<warning, registering>
+
+The C<warnings> pragma provides a number of functions that are useful for
+module authors. These are used when you want to report a module-specific
+warning to a calling module has enabled warnings via the C<warnings>
+pragma.
+
+Consider the module C<MyMod::Abc> below.
+
+ package MyMod::Abc;
+
+ use warnings::register;
+
+ sub open {
+ my $path = shift;
+ if ($path !~ m#^/#) {
+ warnings::warn("changing relative path to /var/abc")
+ if warnings::enabled();
+ $path = "/var/abc/$path";
+ }
+ }
+
+ 1;
+
+The call to C<warnings::register> will create a new warnings category
+called "MyMod::Abc", i.e. the new category name matches the current
+package name. The C<open> function in the module will display a warning
+message if it gets given a relative path as a parameter. This warnings
+will only be displayed if the code that uses C<MyMod::Abc> has actually
+enabled them with the C<warnings> pragma like below.
+
+ use MyMod::Abc;
+ use warnings 'MyMod::Abc';
+ ...
+ abc::open("../fred.txt");
+
+It is also possible to test whether the pre-defined warnings categories are
+set in the calling module with the C<warnings::enabled> function. Consider
+this snippet of code:
+
+ package MyMod::Abc;
+
+ sub open {
+ if (warnings::enabled("deprecated")) {
+ warnings::warn("deprecated",
+ "open is deprecated, use new instead");
+ }
+ new(@_);
+ }
+
+ sub new
+ ...
+ 1;
+
+The function C<open> has been deprecated, so code has been included to
+display a warning message whenever the calling module has (at least) the
+"deprecated" warnings category enabled. Something like this, say.
+
+ use warnings 'deprecated';
+ use MyMod::Abc;
+ ...
+ MyMod::Abc::open($filename);
+
+Either the C<warnings::warn> or C<warnings::warnif> function should be
+used to actually display the warnings message. This is because they can
+make use of the feature that allows warnings to be escalated into fatal
+errors. So in this case
+
+ use MyMod::Abc;
+ use warnings FATAL => 'MyMod::Abc';
+ ...
+ MyMod::Abc::open('../fred.txt');
+
+the C<warnings::warnif> function will detect this and die after
+displaying the warning message.
+
+The three warnings functions, C<warnings::warn>, C<warnings::warnif>
+and C<warnings::enabled> can optionally take an object reference in place
+of a category name. In this case the functions will use the class name
+of the object as the warnings category.
+
+Consider this example:
+
+ package Original;
+
+ no warnings;
+ use warnings::register;
+
+ sub new
+ {
+ my $class = shift;
+ bless [], $class;
+ }
+
+ sub check
+ {
+ my $self = shift;
+ my $value = shift;
+
+ if ($value % 2 && warnings::enabled($self))
+ { warnings::warn($self, "Odd numbers are unsafe") }
+ }
+
+ sub doit
+ {
+ my $self = shift;
+ my $value = shift;
+ $self->check($value);
+ # ...
+ }
+
+ 1;
+
+ package Derived;
+
+ use warnings::register;
+ use Original;
+ our @ISA = qw( Original );
+ sub new
+ {
+ my $class = shift;
+ bless [], $class;
+ }
+
+
+ 1;
+
+The code below makes use of both modules, but it only enables warnings from
+C<Derived>.
+
+ use Original;
+ use Derived;
+ use warnings 'Derived';
+ my $a = Original->new();
+ $a->doit(1);
+ my $b = Derived->new();
+ $a->doit(1);
+
+When this code is run only the C<Derived> object, C<$b>, will generate
+a warning.
+
+ Odd numbers are unsafe at main.pl line 7
+
+Notice also that the warning is reported at the line where the object is first
+used.
+
+When registering new categories of warning, you can supply more names to
+warnings::register like this:
+
+ package MyModule;
+ use warnings::register qw(format precision);
+
+ ...
+
+ warnings::warnif('MyModule::format', '...');
+
+=head1 FUNCTIONS
+
+Note: The functions with names ending in C<_at_level> were added in Perl
+5.28.
+
+=over 4
+
+=item use warnings::register
+
+Creates a new warnings category with the same name as the package where
+the call to the pragma is used.
+
+=item warnings::enabled()
+
+Use the warnings category with the same name as the current package.
+
+Return TRUE if that warnings category is enabled in the calling module.
+Otherwise returns FALSE.
+
+=item warnings::enabled($category)
+
+Return TRUE if the warnings category, C<$category>, is enabled in the
+calling module.
+Otherwise returns FALSE.
+
+=item warnings::enabled($object)
+
+Use the name of the class for the object reference, C<$object>, as the
+warnings category.
+
+Return TRUE if that warnings category is enabled in the first scope
+where the object is used.
+Otherwise returns FALSE.
+
+=item warnings::enabled_at_level($category, $level)
+
+Like C<warnings::enabled>, but $level specifies the exact call frame, 0
+being the immediate caller.
+
+=item warnings::fatal_enabled()
+
+Return TRUE if the warnings category with the same name as the current
+package has been set to FATAL in the calling module.
+Otherwise returns FALSE.
+
+=item warnings::fatal_enabled($category)
+
+Return TRUE if the warnings category C<$category> has been set to FATAL in
+the calling module.
+Otherwise returns FALSE.
+
+=item warnings::fatal_enabled($object)
+
+Use the name of the class for the object reference, C<$object>, as the
+warnings category.
+
+Return TRUE if that warnings category has been set to FATAL in the first
+scope where the object is used.
+Otherwise returns FALSE.
+
+=item warnings::fatal_enabled_at_level($category, $level)
+
+Like C<warnings::fatal_enabled>, but $level specifies the exact call frame,
+0 being the immediate caller.
+
+=item warnings::warn($message)
+
+Print C<$message> to STDERR.
+
+Use the warnings category with the same name as the current package.
+
+If that warnings category has been set to "FATAL" in the calling module
+then die. Otherwise return.
+
+=item warnings::warn($category, $message)
+
+Print C<$message> to STDERR.
+
+If the warnings category, C<$category>, has been set to "FATAL" in the
+calling module then die. Otherwise return.
+
+=item warnings::warn($object, $message)
+
+Print C<$message> to STDERR.
+
+Use the name of the class for the object reference, C<$object>, as the
+warnings category.
+
+If that warnings category has been set to "FATAL" in the scope where C<$object>
+is first used then die. Otherwise return.
+
+=item warnings::warn_at_level($category, $level, $message)
+
+Like C<warnings::warn>, but $level specifies the exact call frame,
+0 being the immediate caller.
+
+=item warnings::warnif($message)
+
+Equivalent to:
+
+ if (warnings::enabled())
+ { warnings::warn($message) }
+
+=item warnings::warnif($category, $message)
+
+Equivalent to:
+
+ if (warnings::enabled($category))
+ { warnings::warn($category, $message) }
+
+=item warnings::warnif($object, $message)
+
+Equivalent to:
+
+ if (warnings::enabled($object))
+ { warnings::warn($object, $message) }
+
+=item warnings::warnif_at_level($category, $level, $message)
+
+Like C<warnings::warnif>, but $level specifies the exact call frame,
+0 being the immediate caller.
+
+=item warnings::register_categories(@names)
+
+This registers warning categories for the given names and is primarily for
+use by the warnings::register pragma.
+
+=back
+
+See also L<perlmodlib/Pragmatic Modules> and L<perldiag>.
+
+=cut
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