X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCarp.pm;h=52ccd76092dc25eb72a2a68d8c014e8e5c45fdab;hb=810a0276062cd558105294bfe7bf18a98deb624a;hp=364442436b12de045174d192772b96521932c5d0;hpb=e8e6f333fb70a1ac62ee87237d37336cd6767150;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Carp.pm b/lib/Carp.pm index 3644424..52ccd76 100644 --- a/lib/Carp.pm +++ b/lib/Carp.pm @@ -1,5 +1,54 @@ package Carp; +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 + +our $MaxEvalLen = 0; +our $Verbose = 0; +our $CarpLevel = 0; +our $MaxArgLen = 64; # How much of each argument to print. 0 = all. +our $MaxArgNums = 8; # How many arguments to print. 0 = all. + +require Exporter; +our @ISA = ('Exporter'); +our @EXPORT = qw(confess croak carp); +our @EXPORT_OK = qw(cluck verbose longmess shortmess); +our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode + +# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl") +# then the following method will be called by the Exporter which knows +# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word +# 'verbose'. + +sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ } + +# fixed hooks for stashes to point to +sub longmess { goto &longmess_jmp } +sub shortmess { goto &shortmess_jmp } +# these two are replaced when Carp::Heavy is loaded +sub longmess_jmp { + local($@, $!); + 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 @_ } +sub carp { warn shortmess @_ } +sub cluck { warn longmess @_ } + +1; +__END__ + =head1 NAME carp - warn of errors (from perspective of caller) @@ -22,11 +71,65 @@ confess - die of errors with stack backtrace =head1 DESCRIPTION The Carp routines are useful in your own modules because -they act like die() or warn(), but report where the error -was in the code they were called from. Thus if you have a -routine Foo() that has a carp() in it, then the carp() -will report the error as occurring where Foo() was called, -not where carp() was called. +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 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 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 + +=item 1. + +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 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 C<@ISA> +with C<@CARP_NOT>, then this trust relationship is identical to, +"inherits from". + +=item 4. + +Any call from an internal Perl module is safe. (Nothing keeps +user modules from marking themselves as internal to Perl, but +this practice is discouraged.) + +=item 5. + +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 =head2 Forcing a Stack Trace @@ -40,257 +143,95 @@ This feature is enabled by 'importing' the non-existent symbol perl -MCarp=verbose script.pl -or by including the string C in the L +or by including the string C in the PERL5OPT environment variable. -=head1 BUGS +Alternately, you can set the global variable C<$Carp::Verbose> to true. +See the C section below. -The Carp routines don't handle exception objects currently. -If called with a first argument that is a reference, they simply -call die() or warn(), as appropriate. +=head1 GLOBAL VARIABLES -=cut +=head2 $Carp::MaxEvalLen -# This package is heavily used. Be small. Be fast. Be good. +This variable determines how many characters of a string-eval are to +be shown in the output. Use a value of C<0> to show all text. -# Comments added by Andy Wardley 09-Apr-98, based on an -# _almost_ complete understanding of the package. Corrections and -# comments are welcome. +Defaults to C<0>. -# The $CarpLevel variable can be set to "strip off" extra caller levels for -# those times when Carp calls are buried inside other functions. The -# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval -# text and function arguments should be formatted when printed. +=head2 $Carp::MaxArgLen -$CarpLevel = 0; # How many extra package levels to skip on carp. -$MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all. -$MaxArgLen = 64; # How much of each argument to print. 0 = all. -$MaxArgNums = 8; # How many arguments to print. 0 = all. -$Verbose = 0; # If true then make shortmess call longmess instead +This variable determines how many characters of each argument to a +function to print. Use a value of C<0> to show the full length of the +argument. -require Exporter; -@ISA = ('Exporter'); -@EXPORT = qw(confess croak carp); -@EXPORT_OK = qw(cluck verbose); -@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode +Defaults to C<64>. +=head2 $Carp::MaxArgNums -# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl") -# then the following method will be called by the Exporter which knows -# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word -# 'verbose'. +This variable determines how many arguments to each function to show. +Use a value of C<0> to show all arguments to a function call. -sub export_fail { - shift; - $Verbose = shift if $_[0] eq 'verbose'; - return @_; -} +Defaults to C<8>. +=head2 $Carp::Verbose -# longmess() crawls all the way up the stack reporting on all the function -# calls made. The error string, $error, is originally constructed from the -# arguments passed into longmess() via confess(), cluck() or shortmess(). -# This gets appended with the stack trace messages which are generated for -# each function call on the stack. - -sub longmess { - return @_ if ref $_[0]; - my $error = join '', @_; - my $mess = ""; - my $i = 1 + $CarpLevel; - my ($pack,$file,$line,$sub,$hargs,$eval,$require); - my (@a); - # - # crawl up the stack.... - # - while (do { { package DB; @a = caller($i++) } } ) { - # get copies of the variables returned from caller() - ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a; - # - # if the $error error string is newline terminated then it - # is copied into $mess. Otherwise, $mess gets set (at the end of - # the 'else {' section below) to one of two things. The first time - # through, it is set to the "$error at $file line $line" message. - # $error is then set to 'called' which triggers subsequent loop - # iterations to append $sub to $mess before appending the "$error - # at $file line $line" which now actually reads "called at $file line - # $line". Thus, the stack trace message is constructed: - # - # first time: $mess = $error at $file line $line - # subsequent times: $mess .= $sub $error at $file line $line - # ^^^^^^ - # "called" - if ($error =~ m/\n$/) { - $mess .= $error; - } else { - # Build a string, $sub, which names the sub-routine called. - # This may also be "require ...", "eval '...' or "eval {...}" - if (defined $eval) { - if ($require) { - $sub = "require $eval"; - } else { - $eval =~ s/([\\\'])/\\$1/g; - if ($MaxEvalLen && length($eval) > $MaxEvalLen) { - substr($eval,$MaxEvalLen) = '...'; - } - $sub = "eval '$eval'"; - } - } elsif ($sub eq '(eval)') { - $sub = 'eval {...}'; - } - # if there are any arguments in the sub-routine call, format - # them according to the format variables defined earlier in - # this file and join them onto the $sub sub-routine string - if ($hargs) { - # we may trash some of the args so we take a copy - @a = @DB::args; # must get local copy of args - # don't print any more than $MaxArgNums - if ($MaxArgNums and @a > $MaxArgNums) { - # cap the length of $#a and set the last element to '...' - $#a = $MaxArgNums; - $a[$#a] = "..."; - } - for (@a) { - # set args to the string "undef" if undefined - $_ = "undef", next unless defined $_; - if (ref $_) { - # dunno what this is for... - $_ .= ''; - s/'/\\'/g; - } - else { - s/'/\\'/g; - # terminate the string early with '...' if too long - substr($_,$MaxArgLen) = '...' - if $MaxArgLen and $MaxArgLen < length; - } - # 'quote' arg unless it looks like a number - $_ = "'$_'" unless /^-?[\d.]+$/; - # print high-end chars as 'M-' or '^' - s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg; - s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg; - } - # append ('all', 'the', 'arguments') to the $sub string - $sub .= '(' . join(', ', @a) . ')'; - } - # here's where the error message, $mess, gets constructed - $mess .= "\t$sub " if $error eq "called"; - $mess .= "$error at $file line $line"; - if (exists $main::{'Thread::'}) { - my $tid = Thread->self->tid; - $mess .= " thread $tid" if $tid; - } - $mess .= "\n"; - } - # we don't need to print the actual error message again so we can - # change this to "called" so that the string "$error at $file line - # $line" makes sense as "called at $file line $line". - $error = "called"; - } - # this kludge circumvents die's incorrect handling of NUL - my $msg = \($mess || $error); - $$msg =~ tr/\0//d; - $$msg; -} +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>. -# shortmess() is called by carp() and croak() to skip all the way up to -# the top-level caller's package and report the error from there. confess() -# and cluck() generate a full stack trace so they call longmess() to -# generate that. In verbose mode shortmess() calls longmess() so -# you always get a stack trace - -sub shortmess { # Short-circuit &longmess if called via multiple packages - goto &longmess if $Verbose; - return @_ if ref $_[0]; - my $error = join '', @_; - my ($prevpack) = caller(1); - my $extra = $CarpLevel; - my $i = 2; - my ($pack,$file,$line); - # when reporting an error, we want to report it from the context of the - # calling package. So what is the calling package? Within a module, - # there may be many calls between methods and perhaps between sub-classes - # and super-classes, but the user isn't interested in what happens - # inside the package. We start by building a hash array which keeps - # track of all the packages to which the calling package belongs. We - # do this by examining its @ISA variable. Any call from a base class - # method (one of our caller's @ISA packages) can be ignored - my %isa = ($prevpack,1); - - # merge all the caller's @ISA packages into %isa. - @isa{@{"${prevpack}::ISA"}} = () - if(@{"${prevpack}::ISA"}); - - # now we crawl up the calling stack and look at all the packages in - # there. For each package, we look to see if it has an @ISA and then - # we see if our caller features in that list. That would imply that - # our caller is a derived class of that package and its calls can also - # be ignored - while (($pack,$file,$line) = caller($i++)) { - if(@{$pack . "::ISA"}) { - my @i = @{$pack . "::ISA"}; - my %i; - @i{@i} = (); - # merge any relevant packages into %isa - @isa{@i,$pack} = () - if(exists $i{$prevpack} || exists $isa{$pack}); - } - - # and here's where we do the ignoring... if the package in - # question is one of our caller's base or derived packages then - # we can ignore it (skip it) and go onto the next (but note that - # the continue { } block below gets called every time) - next - if(exists $isa{$pack}); - - # Hey! We've found a package that isn't one of our caller's - # clan....but wait, $extra refers to the number of 'extra' levels - # we should skip up. If $extra > 0 then this is a false alarm. - # We must merge the package into the %isa hash (so we can ignore it - # if it pops up again), decrement $extra, and continue. - if ($extra-- > 0) { - %isa = ($pack,1); - @isa{@{$pack . "::ISA"}} = () - if(@{$pack . "::ISA"}); - } - else { - # OK! We've got a candidate package. Time to construct the - # relevant error message and return it. die() doesn't like - # to be given NUL characters (which $msg may contain) so we - # remove them first. - my $msg; - $msg = "$error at $file line $line"; - if (exists $main::{'Thread::'}) { - my $tid = Thread->self->tid; - $mess .= " thread $tid" if $tid; - } - $msg .= "\n"; - $msg =~ tr/\0//d; - return $msg; - } - } - continue { - $prevpack = $pack; - } - - # uh-oh! It looks like we crawled all the way up the stack and - # never found a candidate package. Oh well, let's call longmess - # to generate a full stack trace. We use the magical form of 'goto' - # so that this shortmess() function doesn't appear on the stack - # to further confuse longmess() about it's calling package. - goto &longmess; -} +=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: -# the following four functions call longmess() or shortmess() depending on -# whether they should generate a full stack trace (confess() and cluck()) -# or simply report the caller's package (croak() and carp()), respectively. -# confess() and croak() die, carp() and cluck() warn. + $Carp::Internal{ __PACKAGE__ }++; + # time passes... + sub foo { ... or confess("whatever") }; -sub croak { die shortmess @_ } -sub confess { die longmess @_ } -sub carp { warn shortmess @_ } -sub cluck { warn longmess @_ } +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 $Carp::CarpLevel + +This variable determines how many additional call frames are to be +skipped that would not otherwise be when reporting where an error +occurred on a call to one of C's functions. It is fairly easy +to count these call frames on calls that generate a full stack +backtrace. However it is much harder to do this accounting for calls +that generate a short message. Usually people skip too many call +frames. If they are lucky they skip enough that C goes all of +the way through the call stack, realizes that something is wrong, and +then generates a full stack backtrace. If they are unlucky then the +error is reported from somewhere misleading very high in the call +stack. + +Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use +C<@CARP_NOT>, C<%Carp::Internal> and %Carp::CarpInternal>. + +Defaults to C<0>. + +=head1 BUGS + +The Carp routines don't handle exception objects currently. +If called with a first argument that is a reference, they simply +call die() or warn(), as appropriate. -1;