X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCarp.pm;h=52ccd76092dc25eb72a2a68d8c014e8e5c45fdab;hb=810a0276062cd558105294bfe7bf18a98deb624a;hp=c0ffb9c5916b00a4e832f4c4d22011596c4cdb80;hpb=8c3d97219390037dbdf177595955b394d8b3290e;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Carp.pm b/lib/Carp.pm index c0ffb9c..52ccd76 100644 --- a/lib/Carp.pm +++ b/lib/Carp.pm @@ -1,6 +1,6 @@ package Carp; -our $VERSION = '1.05'; +our $VERSION = '1.07'; # 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 @@ -28,8 +28,18 @@ sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ } sub longmess { goto &longmess_jmp } sub shortmess { goto &shortmess_jmp } # these two are replaced when Carp::Heavy is loaded -sub longmess_jmp {{ local($@, $!); require Carp::Heavy} goto &longmess_jmp} -sub shortmess_jmp {{ local($@, $!); require Carp::Heavy} goto &shortmess_jmp} +sub longmess_jmp { + local($@, $!); + eval { require Carp::Heavy }; + return $@ if $@; + goto &longmess_real; +} +sub shortmess_jmp { + local($@, $!); + eval { require Carp::Heavy }; + return $@ if $@; + goto &shortmess_real; +} sub croak { die shortmess @_ } sub confess { die longmess @_ } @@ -50,10 +60,6 @@ croak - die of errors (from perspective of caller) 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; @@ -62,30 +68,27 @@ longmess - return the message that cluck and confess produce 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 +or C 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 works, by changing some global variables in the C namespace. See the section on C 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 and c 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 @@ -97,15 +100,15 @@ Any call from a package to itself is safe. =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. @@ -116,8 +119,15 @@ this practice is discouraged.) =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 or C.) + +=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 @@ -141,21 +151,6 @@ See the C section below. =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'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'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 @@ -180,11 +175,57 @@ Defaults to C<8>. =head2 $Carp::Verbose -This variable makes C use the C function at all times. -This effectively means that all calls to C become C and -all calls to C become C. +This variable makes C and C generate stack backtraces +just like C and C. This is how C +is implemented internally. + +Defaults to C<0>. + +=head2 %Carp::Internal + +This says what packages are internal to Perl. C 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 or C. There errors +will not be reported on any lines that are calling packages in +C<%Carp::CarpInternal>. + +For example C itself is listed in C<%Carp::CarpInternal>. +Therefore the full stack backtrace from C will not start +inside of C, and the short message from calling C is +not placed on the line where C was called. + +=head2 $Carp::CarpLevel -Note, this is analogous to using C. +This variable determines how many additional call frames are to be +skipped that would not otherwise be when reporting where an error +occurred on a call to one of C's functions. It is fairly easy +to count these call frames on calls that generate a full stack +backtrace. However it is much harder to do this accounting for calls +that generate a short message. Usually people skip too many call +frames. If they are lucky they skip enough that C goes all of +the way through the call stack, realizes that something is wrong, and +then generates a full stack backtrace. If they are unlucky then the +error is reported from somewhere misleading very high in the call +stack. + +Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use +C<@CARP_NOT>, C<%Carp::Internal> and %Carp::CarpInternal>. Defaults to C<0>.