X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperllexwarn.pod;h=12ce1f6c82ece36aa5f7e2d8f5bc97e343163918;hb=28b41a8090d259cff9b1dd87c0c53b3c4a31e822;hp=cee16875377f8c495a3304bf361fe3e76486cc03;hpb=d3a7d8c7d7e4d69d7d81e4e3e900ec57f07ca07c;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perllexwarn.pod b/pod/perllexwarn.pod index cee1687..12ce1f6 100644 --- a/pod/perllexwarn.pod +++ b/pod/perllexwarn.pod @@ -9,7 +9,7 @@ flag B<-w> and the equivalent Perl variable, C<$^W>. The pragma works just like the existing "strict" pragma. This means that the scope of the warning pragma is limited to the -enclosing block. It also means that that the pragma setting will not +enclosing block. It also means that the pragma setting will not leak across files (via C, C or C). This allows authors to independently define the degree of warning checks that will be applied to their module. @@ -30,18 +30,17 @@ Similarly all warnings are disabled in a block by either of these: For example, consider the code below: use warnings ; - my $a ; - my $b ; + my @a ; { no warnings ; - $b = 2 if $a EQ 3 ; + my $b = @a[0] ; } - $b = 1 if $a NE 3 ; + my $c = @a[0]; The code in the enclosing block has warnings enabled, but the inner -block has them disabled. In this case that means that the use of the C -operator won't trip a C<"Use of EQ is deprecated"> warning, but the use of -C will produce a C<"Use of NE is deprecated"> warning. +block has them disabled. In this case that means the assignment to the +scalar C<$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 @@ -100,7 +99,7 @@ disable compile-time warnings you need to rewrite the code like this: my $b ; chop $b ; } -The other big problem with C<$^W> is that way you can inadvertently +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 will trip a C<"Use of uninitialized value"> warning, whereas @@ -195,7 +194,7 @@ or B<-X> command line flags. =back -The combined effect of 3 & 4 is that it will will allow code which uses +The combined effect of 3 & 4 is that it will allow code which uses the C pragma to control the warning behavior of $^W-type code (using a C) if it really wants to, but not vice-versa. @@ -208,10 +207,12 @@ The current hierarchy is: all -+ | - +- chmod + +- assertions | +- closure | + +- deprecated + | +- exiting | +- glob @@ -222,6 +223,8 @@ The current hierarchy is: | | | +- exec | | + | +- layer + | | | +- newline | | | +- pipe @@ -266,8 +269,6 @@ The current hierarchy is: | | | +- bareword | | - | +- deprecated - | | | +- digit | | | +- parenthesis @@ -286,7 +287,7 @@ The current hierarchy is: | +- taint | - +- umask + +- threads | +- uninitialized | @@ -317,31 +318,60 @@ C pragma in a given scope the cumulative effect is additive. To determine which category a specific warning has been assigned to see L. +Note: In Perl 5.6.1, the lexical warnings category "deprecated" was a +sub-category of the "syntax" category. It is now a top-level category +in its own right. + + =head2 Fatal Warnings The presence of the word "FATAL" in the category list will escalate any warnings detected from the categories specified in the lexical scope -into fatal errors. In the code below, there are 3 places where a -deprecated warning will be detected, the middle one will produce a -fatal error. - +into fatal errors. In the code below, the use of C