print control-character vars readably

[p5sagit/p5-mst-13.2.git] / ext / B / B.pm

diff --git a/ext/B/B.pm b/ext/B/B.pm
index 591b581..6c2f013 100644 (file)
--- a/ext/B/B.pm
+++ b/ext/B/B.pm
@@ -60,6 +60,12 @@ use strict;
     package B::OBJECT;
 }
 
+sub B::GV::SAFENAME {
+  my $name = (shift())->NAME;
+  $name =~ s/^([\cA-\cZ])/"^".chr(64 + ord($1))/e;
+  return $name;
+}
+
 my $debug;
 my $op_count = 0;
 my @parents = ();
@@ -131,6 +137,7 @@ sub objsym {
 
 sub walkoptree_exec {
     my ($op, $method, $level) = @_;
+    $level ||= 0;
     my ($sym, $ppname);
     my $prefix = "    " x $level;
     for (; $$op; $op = $op->next) {
@@ -364,6 +371,22 @@ C<REFCNT> (corresponding to the C function C<SvREFCNT>).
 
 =item PV
 
+This method is the one you usually want. It constructs a
+string using the length and offset information in the struct:
+for ordinary scalars it will return the string that you'd see
+from Perl, even if it contains null characters.
+
+=item PVX
+
+This method is less often useful. It assumes that the string
+stored in the struct is null-terminated, and disregards the
+length information.
+
+It is the appropriate method to use if you need to get the name
+of a lexical variable from a padname array. Lexical variable names
+are always stored with a null terminator, and the length field
+(SvCUR) is overloaded for other purposes and can't be relied on here.
+
 =back
 
 =head2 B::PVMG METHODS
@@ -432,6 +455,21 @@ This method returns TRUE if the GP field of the GV is NULL.
 
 =item NAME
 
+=item SAFENAME
+
+This method returns the name of the glob, but if the first
+character of the name is a control character, then it converts
+it to ^X first, so that *^G would return "^G" rather than "\cG".
+
+It's useful if you want to print out the name of a variable.
+If you restrict yourself to globs which exist at compile-time
+then the result ought to be unambiguous, because code like
+C<${"^G"} = 1> is compiled as two ops - a constant string and
+a dereference (rv2gv) - so that the glob is created at runtime.
+
+If you're working with globs at runtime, and need to disambiguate
+*^G from *{"^G"}, then you should use the raw NAME method.
+
 =item STASH
 
 =item SV