channels.pm

autoconf是一个产生可以自动配置源代码包

# Copyright (C) 2002, 2004, 2006 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

###############################################################
# The main copy of this file is in Automake's CVS repository. #
# Updates should be sent to [e-mail].         #
###############################################################

package Autom4te::Channels;

=head1 NAME

Autom4te::Channels - support functions for error and warning management

=head1 SYNOPSIS

  use Autom4te::Channels;

  # Register a channel to output warnings about unused variables.
  register_channel 'unused', type => 'warning';

  # Register a channel for system errors.
  register_channel 'system', type => 'error', exit_code => 4;

  # Output a message on channel 'unused'.
  msg 'unused', "$file:$line", "unused variable `$var'";

  # Make the 'unused' channel silent.
  setup_channel 'unused', silent => 1;

  # Turn on all channels of type 'warning'.
  setup_channel_type 'warning', silent => 0;

  # Treat all warnings as errors.
  $warnings_are_errors = 1;

  # Exit with the greatest exit code encountered so far.
  exit $exit_code;

=head1 DESCRIPTION

This perl module provides support functions for handling diagnostic
channels in programs.  Channels can be registered to convey fatal,
error, warning, or debug messages.  Each channel has various options
(e.g. is the channel silent, should duplicate messages be removed,
etc.) that can also be overridden on a per-message basis.

=cut

use 5.005;
use strict;
use Exporter;
use Carp;
use File::Basename;

use vars qw (@ISA @EXPORT %channels $me);

@ISA = qw (Exporter);
@EXPORT = qw ($exit_code $warnings_are_errors
	      &reset_local_duplicates &reset_global_duplicates
	      &register_channel &msg &exists_channel &channel_type
	      &setup_channel &setup_channel_type
	      &dup_channel_setup &drop_channel_setup
	      &buffer_messages &flush_messages
	      US_GLOBAL US_LOCAL
	      UP_NONE UP_TEXT UP_LOC_TEXT);

$me = basename $0;

=head2 Global Variables

=over 4

=item C<$exit_code>

The greatest exit code seen so far. C<$exit_code> is updated from
the C<exit_code> options of C<fatal> and C<error> channels.

=cut

use vars qw ($exit_code);
$exit_code = 0;

=item C<$warnings_are_errors>

Set this variable to 1 if warning messages should be treated as
errors (i.e. if they should update C<$exit_code>).

=cut

use vars qw ($warnings_are_errors);
$warnings_are_errors = 0;

=back

=head2 Constants

=over 4

=item C<UP_NONE>, C<UP_TEXT>, C<UP_LOC_TEXT>

Possible values for the C<uniq_part> options.  This selects the part
of the message that should be considered when filtering out duplicates.
If C<UP_LOC_TEXT> is used, the location and the explanation message
are used for filtering.  If C<UP_TEXT> is used, only the explanation
message is used (so the same message will be filtered out if it appears
at different locations).  C<UP_NONE> means that duplicate messages
should be output.

=cut

use constant UP_NONE => 0;
use constant UP_TEXT => 1;
use constant UP_LOC_TEXT => 2;

=item C<US_LOCAL>, C<US_GLOBAL>

Possible values for the C<uniq_scope> options.
Use C<US_GLOBAL> for error messages that should be printed only
once during the execution of the program, C<US_LOCAL> for message that
should be printed only once per file.  (Actually, C<Channels> does not
do this now when files are changed, it relies on you calling
C<reset_local_duplicates> when this happens.)

=cut

# possible values for uniq_scope
use constant US_LOCAL => 0;
use constant US_GLOBAL => 1;

=back

=head2 Options

Channels accept the options described below.  These options can be
passed as a hash to the C<register_channel>, C<setup_channel>, and C<msg>
functions.  The possible keys, with their default value are:

=over

=item C<type =E<gt> 'warning'>

The type of the channel.  One of C<'debug'>, C<'warning'>, C<'error'>, or
C<'fatal'>.  Fatal messages abort the program when they are output.
Error messages update the exit status.  Debug and warning messages are
harmless, except that warnings can be treated as errors of
C<$warnings_are_errors> is set.

=item C<exit_code =E<gt> 1>

The value to update C<$exit_code> with when a fatal or error message
is emitted.  C<$exit_code> is also updated for warnings output
when @<$warnings_are_errors> is set.

=item C<file =E<gt> \*STDERR>

The file where the error should be output.

=item C<silent =E<gt> 0>

Whether the channel should be silent.  Use this do disable a
category of warning, for instance.

=item C<uniq_part =E<gt> UP_LOC_TEXT>

The part of the message subject to duplicate filtering.  See the
documentation for the C<UP_NONE>, C<UP_TEXT>, and C<UP_LOC_TEXT>
constants above.

C<uniq_part> can also be set to an arbitrary string that will be used
instead of the message when considering duplicates.

=item C<uniq_scope =E<gt> US_LOCAL>

The scope of duplicate filtering.  See the documentation for the
C<US_LOCAL>, and C<US_GLOBAL> constants above.

=item C<header =E<gt> ''>

A string to prepend to each message emitted through this channel.

=item C<footer =E<gt> ''>

A string to append to each message emitted through this channel.

=item C<backtrace =E<gt> 0>

Die with a stack backtrace after displaying the message.

=item C<partial =E<gt> 0>

When set, indicates a partial message that should
be output along with the next message with C<partial> unset.
Several partial messages can be stacked this way.

Duplicate filtering will apply to the I<global> message resulting from
all I<partial> messages, using the options from the last (non-partial)
message.  Linking associated messages is the main reason to use this
option.

For instance the following messages

  msg 'channel', 'foo:2', 'redefinition of A ...';
  msg 'channel', 'foo:1', '... A previously defined here';
  msg 'channel', 'foo:3', 'redefinition of A ...';
  msg 'channel', 'foo:1', '... A previously defined here';

will result in

 foo:2: redefinition of A ...
 foo:1: ... A previously defined here
 foo:3: redefinition of A ...

where the duplicate "I<... A previously defined here>" has been
filtered out.

Linking these messages using C<partial> as follows will prevent the
fourth message to disappear.

  msg 'channel', 'foo:2', 'redefinition of A ...', partial => 1;
  msg 'channel', 'foo:1', '... A previously defined here';
  msg 'channel', 'foo:3', 'redefinition of A ...', partial => 1;
  msg 'channel', 'foo:1', '... A previously defined here';

Note that because the stack of C<partial> messages is printed with the
first non-C<partial> message, most options of C<partial> messages will
be ignored.

=back

=cut

use vars qw (%_default_options %_global_duplicate_messages
	     %_local_duplicate_messages);

# Default options for a channel.
%_default_options =
  (
   type => 'warning',
   exit_code => 1,
   file => \*STDERR,
   silent => 0,
   uniq_scope => US_LOCAL,
   uniq_part => UP_LOC_TEXT,
   header => '',
   footer => '',
   backtrace => 0,
   partial => 0,
   );

# Filled with output messages as keys, to detect duplicates.
# The value associated with each key is the number of occurrences
# filtered out.
%_local_duplicate_messages = ();
%_global_duplicate_messages = ();

sub _reset_duplicates (\%)
{
  my ($ref) = @_;
  my $dup = 0;
  foreach my $k (keys %$ref)
    {
      $dup += $ref->{$k};
    }
  %$ref = ();
  return $dup;
}


=head2 Functions

=over 4

=item C<reset_local_duplicates ()>

Reset local duplicate messages (see C<US_LOCAL>), and
return the number of messages that have been filtered out.

=cut

sub reset_local_duplicates ()
{
  return _reset_duplicates %_local_duplicate_messages;
}

=item C<reset_global_duplicates ()>

Reset local duplicate messages (see C<US_GLOBAL>), and
return the number of messages that have been filtered out.

=cut

sub reset_global_duplicates ()
{
  return _reset_duplicates %_global_duplicate_messages;
}

sub _merge_options (\%%)
{
  my ($hash, %options) = @_;
  local $_;

  foreach (keys %options)
    {
      if (exists $hash->{$_})
	{
	  $hash->{$_} = $options{$_}
	}
      else
	{
	  confess "unknown option `$_'";
	}
    }
}

=item C<register_channel ($name, [%options])>

Declare channel C<$name>, and override the default options
with those listed in C<%options>.

=cut

sub register_channel ($;%)
{
  my ($name, %options) = @_;
  my %channel_opts = %_default_options;
  _merge_options %channel_opts, %options;
  $channels{$name} = \%channel_opts;
}

=item C<exists_channel ($name)>

Returns true iff channel C<$name> has been registered.

=cut

sub exists_channel ($)
{
  my ($name) = @_;
  return exists $channels{$name};
}