Snapshot of the dynamic call stack
class Backtrace {}
A backtrace contains the dynamic call stack, usually leading up to a point where an exception was thrown, and is a List of Backtrace::Frame objects. Its default stringification excludes backtrace frames that are deemed unnecessary or confusing; for example routines like &die are hidden by default. Being a list, you can also access individual elements.
sub zipi { { { die "Something bad happened" }() }() };
try {
zipi;
}
if ($!) {
say $!.backtrace[*-1].raku;
}
This will print the last frame in the list, pointing at the line where it's happened.
multi method new()
multi method new(Int:D $offset)
multi method new(Mu \ex)
multi method new(Mu \ex, Int:D $offset)
multi method new(List:D $bt)
multi method new(List:D $bt, Int:D $offset)
Creates a new backtrace, using its calling location as the origin of the backtrace or the $offset that is passed as a parameter. If an object or a list (that will already contain a backtrace in list form) is passed, they will be used instead of the current code.
my $backtrace = Backtrace.new;
multi method gist(Backtrace:D:)
Returns string "Backtrace(42 frames)" where the number indicates the number of frames available via list method.
multi method Str(Backtrace:D:)
Returns a concise string representation of the backtrace, omitting routines marked as is hidden-from-backtrace, and at the discretion of the implementation, also some routines from the setting.
my $backtrace = Backtrace.new;
say $backtrace.Str;
method next-interesting-index(Backtrace:D: Int $idx = 0, :$named, :$noproto, :$setting)
Returns the index of the next interesting frame, once hidden and other settings are taken into account. $named will decide whether to printed only those with a name, $noproto will hide protos, and $setting will hide those are considered setting.
sub zipi { { { die "Something bad happened" }() }() };
try zipi;
say $!.backtrace.next-interesting-index; # OUTPUT: «2»
say $!.backtrace.next-interesting-index( :named ); # OUTPUT: «4»
method outer-caller-idx(Backtrace:D: Int $startidx)
Returns as a list the index of the frames that called the current one.
sub zipi { { { die "Something bad happened" }() }() };
try zipi;
say $!.backtrace.outer-caller-idx( 4 ); # OUTPUT: «[6]»
method nice(Backtrace:D: :$oneline)
Returns the backtrace as a list of interesting frames. If :$oneline is set, will stop after the first frame.
sub zipi { { { die "Something bad happened" }() }() };
try zipi;
say $!.backtrace.nice( :oneline ) if $!;
# OUTPUT: « in sub zipi at /tmp/... line 1»
multi method full(Backtrace:D:)
Returns a full string representation of the backtrace, including hidden frames, compiler-specific frames, and those from the setting.
my $backtrace = Backtrace.new;
say $backtrace.full;
multi method list(Backtrace:D:)
Returns a list of Backtrace::Frame objects for this backtrace.
method summary(Backtrace:D: --> Str:D)
Returns a summary string representation of the backtrace, filtered by !.is-hidden && (.is-routine || !.is-setting).
This program:
sub inner { say Backtrace.new.summary }
sub outer { inner; }
outer;
results in:
in method new at SETTING::src/core.c/Backtrace.rakumod line 85 in sub inner at test.raku line 1 in sub outer at test.raku line 2 in block <unit> at test.raku line 3
method concise(Backtrace:D:)
Returns a concise string representation of the backtrace, filtered by !.is-hidden && .is-routine && !.is-setting.
This program:
sub inner { say Backtrace.new.concise }
sub outer { inner; }
outer;
results in:
in sub inner at test.raku line 1 in sub outer at test.raku line 2
multi method map(Backtrace:D: &block --> Seq:D)
It invokes &block for each element and gathers the return values in a sequence and returns it.
This program:
sub inner { Backtrace.new.map({ say "{$_.file}: {$_.line}" }); }
sub outer { inner; }
outer;
results in:
SETTING::src/core.c/Backtrace.rakumod: 85 SETTING::src/core.c/Backtrace.rakumod: 85 test.raku: 1 test.raku: 2 test.raku: 3 test.raku: 1
multi method flat(Backtrace:D:)
Returns the backtrace same as list.