package Carp;
-our $VERSION = '1.05';
+our $VERSION = '1.08';
# this file is an utra-lightweight stub. The first time a function is
# called, Carp::Heavy is loaded, and the real short/longmessmess_jmp
# subs are installed
local($@, $!);
eval { require Carp::Heavy };
return $@ if $@;
- goto &longmess_jmp;
+ goto &longmess_real;
}
sub shortmess_jmp {
local($@, $!);
eval { require Carp::Heavy };
return $@ if $@;
- goto &shortmess_jmp;
+ goto &shortmess_real;
}
sub croak { die shortmess @_ }
confess - die of errors with stack backtrace
-shortmess - return the message that carp and croak produce
-
-longmess - return the message that cluck and confess produce
-
=head1 SYNOPSIS
use Carp;
use Carp qw(cluck);
cluck "This is how we got here!";
- print FH Carp::shortmess("This will have caller's details added");
- print FH Carp::longmess("This will have stack backtrace added");
-
=head1 DESCRIPTION
The Carp routines are useful in your own modules because
they act like die() or warn(), but with a message which is more
likely to be useful to a user of your module. In the case of
cluck, confess, and longmess that context is a summary of every
-call in the call-stack. For a shorter message you can use carp,
-croak or shortmess which report the error as being from where
-your module was called. There is no guarantee that that is where
-the error was, but it is a good educated guess.
+call in the call-stack. For a shorter message you can use C<carp>
+or C<croak> which report the error as being from where your module
+was called. There is no guarantee that that is where the error
+was, but it is a good educated guess.
You can also alter the way the output and logic of C<Carp> works, by
changing some global variables in the C<Carp> namespace. See the
section on C<GLOBAL VARIABLES> below.
-Here is a more complete description of how shortmess works. What
-it does is search the call-stack for a function call stack where
-it hasn't been told that there shouldn't be an error. If every
-call is marked safe, it then gives up and gives a full stack
-backtrace instead. In other words it presumes that the first likely
-looking potential suspect is guilty. Its rules for telling whether
+Here is a more complete description of how c<carp> and c<croak> work.
+What they do is search the call-stack for a function call stack where
+they have not been told that there shouldn't be an error. If every
+call is marked safe, they give up and give a full stack backtrace
+instead. In other words they presume that the first likely looking
+potential suspect is guilty. Their rules for telling whether
a call shouldn't generate errors work as follows:
=over 4
=item 2.
Packages claim that there won't be errors on calls to or from
-packages explicitly marked as safe by inclusion in @CARP_NOT, or
-(if that array is empty) @ISA. The ability to override what
+packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or
+(if that array is empty) C<@ISA>. The ability to override what
@ISA says is new in 5.8.
=item 3.
The trust in item 2 is transitive. If A trusts B, and B
-trusts C, then A trusts C. So if you do not override @ISA
-with @CARP_NOT, then this trust relationship is identical to,
+trusts C, then A trusts C. So if you do not override C<@ISA>
+with C<@CARP_NOT>, then this trust relationship is identical to,
"inherits from".
=item 4.
=item 5.
-Any call to Carp is safe. (This rule is what keeps it from
-reporting the error where you call carp/croak/shortmess.)
+Any call to Perl's warning system (eg Carp itself) is safe.
+(This rule is what keeps it from reporting the error at the
+point where you call C<carp> or C<croak>.)
+
+=item 6.
+
+C<$Carp::CarpLevel> can be set to skip a fixed number of additional
+call levels. Using this is not recommended because it is very
+difficult to get it to behave correctly.
=back
=head1 GLOBAL VARIABLES
-=head2 $Carp::CarpLevel
-
-This variable determines how many call frames are to be skipped when
-reporting where an error occurred on a call to one of C<Carp>'s
-functions. For example:
-
- $Carp::CarpLevel = 1;
- sub bar { .... or _error('Wrong input') }
- sub _error { Carp::carp(@_) }
-
-This would make Carp report the error as coming from C<bar>'s caller,
-rather than from C<_error>'s caller, as it normally would.
-
-Defaults to C<0>.
-
=head2 $Carp::MaxEvalLen
This variable determines how many characters of a string-eval are to
=head2 $Carp::Verbose
-This variable makes C<Carp> use the C<longmess> function at all times.
-This effectively means that all calls to C<carp> become C<cluck> and
-all calls to C<croak> become C<confess>.
+This variable makes C<carp> and C<cluck> generate stack backtraces
+just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
+is implemented internally.
+
+Defaults to C<0>.
+
+=head2 %Carp::Internal
+
+This says what packages are internal to Perl. C<Carp> will never
+report an error as being from a line in a package that is internal to
+Perl. For example:
+
+ $Carp::Internal{ __PACKAGE__ }++;
+ # time passes...
+ sub foo { ... or confess("whatever") };
+
+would give a full stack backtrace starting from the first caller
+outside of __PACKAGE__. (Unless that package was also internal to
+Perl.)
+
+=head2 %Carp::CarpInternal
+
+This says which packages are internal to Perl's warning system. For
+generating a full stack backtrace this is the same as being internal
+to Perl, the stack backtrace will not start inside packages that are
+listed in C<%Carp::CarpInternal>. But it is slightly different for
+the summary message generated by C<carp> or C<croak>. There errors
+will not be reported on any lines that are calling packages in
+C<%Carp::CarpInternal>.
+
+For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
+Therefore the full stack backtrace from C<confess> will not start
+inside of C<Carp>, and the short message from calling C<croak> is
+not placed on the line where C<croak> was called.
+
+=head2 $Carp::CarpLevel
-Note, this is analogous to using C<use Carp 'verbose'>.
+This variable determines how many additional call frames are to be
+skipped that would not otherwise be when reporting where an error
+occurred on a call to one of C<Carp>'s functions. It is fairly easy
+to count these call frames on calls that generate a full stack
+backtrace. However it is much harder to do this accounting for calls
+that generate a short message. Usually people skip too many call
+frames. If they are lucky they skip enough that C<Carp> goes all of
+the way through the call stack, realizes that something is wrong, and
+then generates a full stack backtrace. If they are unlucky then the
+error is reported from somewhere misleading very high in the call
+stack.
+
+Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use
+C<@CARP_NOT>, C<%Carp::Internal> and %Carp::CarpInternal>.
Defaults to C<0>.
https://perl5.git.perl.org / perl5.git / blobdiff