From: Paul Marquess <paul.marquess@btinternet.com>
Date: Mon, 28 Aug 2000 23:55:06 +0000 (+0100)
Subject: warnings fixes
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=f1f338184e4a44fc14036174dbaf0664efde29d6;p=p5sagit%2Fp5-mst-13.2.git

warnings fixes
Message-ID: <000501c01143$0230af80$2014140a@bfs.phone.com>

p4raw-id: //depot/perl@6869
---

diff --git a/lib/warnings.pm b/lib/warnings.pm
index df9f787..2517239 100644
--- a/lib/warnings.pm
+++ b/lib/warnings.pm
@@ -303,14 +303,19 @@ sub bits {
 
 sub import {
     shift;
-    ${^WARNING_BITS} |= bits(@_ ? @_ : 'all') ;
+    my $mask = ${^WARNING_BITS} ;
+    if (vec($mask, $Offsets{'all'}, 1)) {
+        $mask |= $Bits{'all'} ;
+        $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
+    }
+    ${^WARNING_BITS} = $mask | bits(@_ ? @_ : 'all') ;
 }
 
 sub unimport {
     shift;
     my $mask = ${^WARNING_BITS} ;
     if (vec($mask, $Offsets{'all'}, 1)) {
-        $mask = $Bits{'all'} ;
+        $mask |= $Bits{'all'} ;
         $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
     }
     ${^WARNING_BITS} = $mask & ~ (bits(@_ ? @_ : 'all') | $All) ;
diff --git a/pod/perllexwarn.pod b/pod/perllexwarn.pod
index efc0196..3dd3ba9 100644
--- a/pod/perllexwarn.pod
+++ b/pod/perllexwarn.pod
@@ -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<EQ>
-operator won't trip a C<"Use of EQ is deprecated"> warning, but the use of
-C<NE> 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<doit> will trip a C<"Use of uninitialized value"> warning, whereas
@@ -321,21 +320,32 @@ L<perldiag>.
 
 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<time>, C<length>
+and C<join> can all produce a C<"Useless use of xxx in void context">
+warning.
 
     use warnings ;
-
-    $a = 1 if $a EQ $b ;
-
+ 
+    time ;
+ 
     {
-        use warnings FATAL => qw(deprecated) ;
-        $a = 1 if $a EQ $b ;
+        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 it
+encounters the warning.
 
-    $a = 1 if $a EQ $b ;
 
 =head2 Reporting Warnings from a Module
 
diff --git a/t/pragma/warn/7fatal b/t/pragma/warn/7fatal
index 382a845..a25fa2c 100644
--- a/t/pragma/warn/7fatal
+++ b/t/pragma/warn/7fatal
@@ -276,3 +276,37 @@ $a =+ 1 ;
 print STDERR "The End.\n" ;
 EXPECT
 Reversed += operator at - line 8.
+########
+
+use warnings 'void' ;
+
+time ;
+
+{
+    use warnings FATAL => qw(void) ;
+    length "abc" ;
+}
+
+join "", 1,2,3 ;
+
+print "done\n" ;
+EXPECT
+Useless use of time in void context at - line 4.
+Useless use of length in void context at - line 8.
+########
+
+use warnings ;
+
+time ;
+
+{
+    use warnings FATAL => qw(void) ;
+    length "abc" ;
+}
+
+join "", 1,2,3 ;
+
+print "done\n" ;
+EXPECT
+Useless use of time in void context at - line 4.
+Useless use of length in void context at - line 8.
diff --git a/warnings.pl b/warnings.pl
index 4be4280..0c2d2ec 100644
--- a/warnings.pl
+++ b/warnings.pl
@@ -473,14 +473,19 @@ sub bits {
 
 sub import {
     shift;
-    ${^WARNING_BITS} |= bits(@_ ? @_ : 'all') ;
+    my $mask = ${^WARNING_BITS} ;
+    if (vec($mask, $Offsets{'all'}, 1)) {
+        $mask |= $Bits{'all'} ;
+        $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
+    }
+    ${^WARNING_BITS} = $mask | bits(@_ ? @_ : 'all') ;
 }
 
 sub unimport {
     shift;
     my $mask = ${^WARNING_BITS} ;
     if (vec($mask, $Offsets{'all'}, 1)) {
-        $mask = $Bits{'all'} ;
+        $mask |= $Bits{'all'} ;
         $mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
     }
     ${^WARNING_BITS} = $mask & ~ (bits(@_ ? @_ : 'all') | $All) ;