"warnings" pragma silently ignores postfixed "FATAL" import parameter #15425
Comments
From the.rob.dixon@gmail.comThis is a bug report for perl from the.rob.dixon@gmail.com, The documentation for the `warnings` pragma has this * The presence of the word "FATAL" in the category list will escalate* which works fine for the examples given, like use warnings FATAL => 'all' This also works fine if the category is defaulted. For instance use warnings 'FATAL' is equivalent to the previous example. `FATAL` may be also used to separate fatal categories from non-fatal ones, use warnings qw/ uninitialized FATAL deprecated experimental / makes "deprecated" and "experimental" warnings fatal while "uninitialized" However the `FATAL` is silently ineffective if it is used without any The doeumentation would have us believe that use warnings qw/ all FATAL / should work fine, but the FATAL has no effect at all and gives no message I suggest that this should result in a compilation failure in the same way Flags: Site configuration information for perl 5.24.0: Configured by strawberry-perl at Tue May 10 21:33:22 2016. Summary of my perl5 (revision 5 version 24 subversion 0) configuration: Platform: @INC for perl 5.24.0: Environment for perl 5.24.0: |
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@dcollinsn - Status changed from 'new' to 'open' |
From @dcollinsnTwo parts to this: one is fixing the documentation (patch 0001), the other is adding the proposed warning (patch 0002). Both seem pretty straightforward. I can't imagine that this is an issue that comes up very often, but it doesn't cost much to add the warning. I tested it (temporarily making it a croak), and ran `make test` - no tests failed (yet), so this doesn't break anything in our test suite that currently works. However, there's no guarantee that somewhere, someone doesn't have something like use warnings 'all', 'FATAL' => @fatal_warnings; who is using this behavior on purpose, and is now going to get an unnecessary warning. Example: $ ./perl -Ilib -e 'use warnings qw(all); $a = test; print "Alive!\n";' |
From @dcollinsn0001-RT-128540-lib-warnings.pm-documentation-for-FATAL.patchFrom 86200781a075b815ae9c9733785bb79f49a93408 Mon Sep 17 00:00:00 2001
From: Dan Collins <dcollinsn@gmail.com>
Date: Tue, 5 Jul 2016 10:41:31 -0400
Subject: [PATCH 1/2] [RT #128540] lib/warnings.pm: documentation for FATAL
---
lib/warnings.pm | 16 +++++++++++++++-
regen/warnings.pl | 16 +++++++++++++++-
2 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/lib/warnings.pm b/lib/warnings.pm
index d607f31..cb7d99c 100644
--- a/lib/warnings.pm
+++ b/lib/warnings.pm
@@ -872,7 +872,8 @@ is now a top-level category in its own right.
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.
+warnings in categories following the word "FATAL" into fatal errors
+in that lexical scope.
B<NOTE:> FATAL warnings should be used with care, particularly
C<< FATAL => 'all' >>.
@@ -959,6 +960,19 @@ except for those in the "syntax" category.
use warnings FATAL => 'all', NONFATAL => 'syntax';
+Note that the location of the word "FATAL" or "NONFATAL" in the argument
+list is relevant, as it only applies to warning categories following it.
+So:
+
+ use warnings qw(all FATAL experimental)
+
+will enable all warnings, but only experimental warnings will be made
+fatal. Similarly:
+
+ use warnings qw(all FATAL)
+
+will not make any warnings fatal.
+
As of Perl 5.20, instead of C<< use warnings FATAL => 'all'; >> you can
use:
diff --git a/regen/warnings.pl b/regen/warnings.pl
index 815c735..4d1cde1 100644
--- a/regen/warnings.pl
+++ b/regen/warnings.pl
@@ -1001,7 +1001,8 @@ is now a top-level category in its own right.
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.
+warnings in categories following the word "FATAL" into fatal errors
+in that lexical scope.
B<NOTE:> FATAL warnings should be used with care, particularly
C<< FATAL => 'all' >>.
@@ -1088,6 +1089,19 @@ except for those in the "syntax" category.
use warnings FATAL => 'all', NONFATAL => 'syntax';
+Note that the location of the word "FATAL" or "NONFATAL" in the argument
+list is relevant, as it only applies to warning categories following it.
+So:
+
+ use warnings qw(all FATAL experimental)
+
+will enable all warnings, but only experimental warnings will be made
+fatal. Similarly:
+
+ use warnings qw(all FATAL)
+
+will not make any warnings fatal.
+
As of Perl 5.20, instead of C<< use warnings FATAL => 'all'; >> you can
use:
--
2.8.1
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From @dcollinsn0002-RT-128540-lib-warnings.pm-warn-for-useless-FATAL.patchFrom 5f919e998f53df04355376129330b70e5c7e7746 Mon Sep 17 00:00:00 2001
From: Dan Collins <dcollinsn@gmail.com>
Date: Tue, 5 Jul 2016 10:42:29 -0400
Subject: [PATCH 2/2] [RT #128540] lib/warnings.pm: warn for useless FATAL
When FATAL (or NONFATAL) is used as the only warnings category,
it is interpreted as FATAL => all. However, when it is used as
the last of several categories, it silently has no effect. This
adds a warning for this case.
---
lib/warnings.pm | 13 +++++++++++++
regen/warnings.pl | 13 +++++++++++++
2 files changed, 26 insertions(+)
diff --git a/lib/warnings.pm b/lib/warnings.pm
index cb7d99c..ee590ee 100644
--- a/lib/warnings.pm
+++ b/lib/warnings.pm
@@ -249,6 +249,14 @@ sub Croaker
Carp::croak(@_);
}
+sub Carper
+{
+ require Carp; # this initializes %CarpInternal
+ local $Carp::CarpInternal{'warnings'};
+ delete $Carp::CarpInternal{'warnings'};
+ Carp::carp(@_);
+}
+
sub _bits {
my $mask = shift ;
my $catmask ;
@@ -299,6 +307,11 @@ sub import
# Empty @_ is equivalent to @_ = 'all' ;
${^WARNING_BITS} = @_ ? _bits($mask, @_) : $mask | $Bits{all} ;
+
+ # Warn if last word of import directive is FATAL or NONFATAL
+ # (except for lone FATAL or NONFATAL)
+ Carper("FATAL or NONFATAL as final warnings category has no effect")
+ if @_>1 && ( $_[-1] eq 'FATAL' || $_[-1] eq 'NONFATAL' );
}
sub unimport
diff --git a/regen/warnings.pl b/regen/warnings.pl
index 4d1cde1..e771b08 100644
--- a/regen/warnings.pl
+++ b/regen/warnings.pl
@@ -508,6 +508,14 @@ sub Croaker
Carp::croak(@_);
}
+sub Carper
+{
+ require Carp; # this initializes %CarpInternal
+ local $Carp::CarpInternal{'warnings'};
+ delete $Carp::CarpInternal{'warnings'};
+ Carp::carp(@_);
+}
+
sub _bits {
my $mask = shift ;
my $catmask ;
@@ -558,6 +566,11 @@ sub import
# Empty @_ is equivalent to @_ = 'all' ;
${^WARNING_BITS} = @_ ? _bits($mask, @_) : $mask | $Bits{all} ;
+
+ # Warn if last word of import directive is FATAL or NONFATAL
+ # (except for lone FATAL or NONFATAL)
+ Carper("FATAL or NONFATAL as final warnings category has no effect")
+ if @_>1 && ( $_[-1] eq 'FATAL' || $_[-1] eq 'NONFATAL' );
}
sub unimport
--
2.8.1
|
From [Unknown Contact. See original ticket]Two parts to this: one is fixing the documentation (patch 0001), the other is adding the proposed warning (patch 0002). Both seem pretty straightforward. I can't imagine that this is an issue that comes up very often, but it doesn't cost much to add the warning. I tested it (temporarily making it a croak), and ran `make test` - no tests failed (yet), so this doesn't break anything in our test suite that currently works. However, there's no guarantee that somewhere, someone doesn't have something like use warnings 'all', 'FATAL' => @fatal_warnings; who is using this behavior on purpose, and is now going to get an unnecessary warning. Example: $ ./perl -Ilib -e 'use warnings qw(all); $a = test; print "Alive!\n";' |
Migrated from rt.perl.org#128540 (status was 'open')
Searchable as RT128540$
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