Regenerate perlguts’ mg table automatically

regen/mg_vtable.pl was modified a while ago to generate the table
for copying and pasting, but at least twice since then it has not
been updated properly; once by me and once by the author of that
part of regen/mg_vtable.pl.

2 files changed, 32 insertions, 12 deletions

diff --git a/pod/perlguts.pod b/pod/perlguts.pod
index 4391975906..6206dadf0b 100644
--- a/pod/perlguts.pod
+++ b/pod/perlguts.pod
@@ -1041,6 +1041,12 @@ to change.
 
 The current kinds of Magic Virtual Tables are:
 
+=for comment
+This table is generated by regen/mg_vtable.pl.  Any changes made here
+will be lost.
+
+=for mg_vtable.pl begin
+
  mg_type
  (old-style char and macro)   MGVTBL          Type of magic
  --------------------------   ------          -------------
@@ -1066,9 +1072,9 @@ The current kinds of Magic Virtual Tables are:
                                               element
  E  PERL_MAGIC_env            vtbl_env        %ENV hash
  e  PERL_MAGIC_envelem        vtbl_envelem    %ENV hash element
- f  PERL_MAGIC_fm             vtbl_regdata    Formline ('compiled'
-                                              format)
- G  PERL_MAGIC_study          vtbl_regdata    study()ed string
+ f  PERL_MAGIC_fm             vtbl_regdata    Formline 
+                                              ('compiled' format)
+ G  PERL_MAGIC_study          vtbl_regexp     study()ed string
  g  PERL_MAGIC_regex_global   vtbl_mglob      m//g target
  H  PERL_MAGIC_hints          vtbl_hints      %^H hash
  h  PERL_MAGIC_hintselem      vtbl_hintselem  %^H hash element
@@ -1092,7 +1098,7 @@ The current kinds of Magic Virtual Tables are:
                                               extensions
  u  PERL_MAGIC_uvar_elem      (none)          Reserved for use by
                                               extensions
- V  PERL_MAGIC_vstring        (none)          SV was vstring literal
+ V  PERL_MAGIC_vstring        vtbl_vstring    SV was vstring literal
  v  PERL_MAGIC_vec            vtbl_vec        vec() lvalue
  w  PERL_MAGIC_utf8           vtbl_utf8       Cached UTF-8 information
  x  PERL_MAGIC_substr         vtbl_substr     substr() lvalue
@@ -1104,6 +1110,7 @@ The current kinds of Magic Virtual Tables are:
  ~  PERL_MAGIC_ext            (none)          Available for use by
                                               extensions
 
+=for mg_vtable.pl end
 
 When an uppercase and lowercase letter both exist in the table, then the
 uppercase letter is typically used to represent some kind of composite type
diff --git a/regen/mg_vtable.pl b/regen/mg_vtable.pl
index 3c3c4840cb..ba59fb02ab 100644
--- a/regen/mg_vtable.pl
+++ b/regen/mg_vtable.pl
@@ -18,9 +18,6 @@ BEGIN {
     require 'regen/regen_lib.pl';
 }
 
-# This generates the relevant section to paste into perlguts.pod to STDOUT
-my $output_guts = grep { $_ eq '-g' } @ARGV;
-
 my %mg =
     (
      sv => { char => '\0', vtable => 'sv', readonly_acceptable => 1,
@@ -151,6 +148,7 @@ my ($vt, $raw, $names) = map {
     open_new($_, '>',
 	     { by => 'regen/mg_vtable.pl', file => $_, style => '*' });
 } 'mg_vtable.h', 'mg_raw.h', 'mg_names.c';
+my $guts = open_new("pod/perlguts.pod", ">");
 
 print $vt <<'EOH';
 /* These constants should be used in preference to raw characters
@@ -216,7 +214,7 @@ EOH
 		     $data->{vtable} ? "vtbl_$data->{vtable}" : '(none)',
 		     $data->{desc}];
     }
-    if ($output_guts) {
+    select +(select($guts), do {
 	my @header = ('(old-style char and macro)', 'MGVTBL', 'Type of magic');
 	my @widths = (0, 0);
 	foreach my $row (@rows) {
@@ -225,12 +223,20 @@ EOH
 		    if length $row->[$_] > $widths[$_];
 	    }
 	}
-	my $indent = '    ';
+	my $indent = ' ';
 	my $format
 	    = sprintf "$indent%%-%ds%%-%ds%%s\n", $widths[0] + 1, $widths[1] + 1;
-	my $desc_wrap = 80 - (length $indent) - $widths[0] - $widths[1] - 2;
+	my $desc_wrap =
+	    79 - 7 - (length $indent) - $widths[0] - $widths[1] - 2;
+
+	open my $oldguts, "<", "pod/perlguts.pod"
+	   or die "$0 cannot open pod/perlguts.pod for reading: $!";
+	while (<$oldguts>) {
+	    print;
+	    last if /^=for mg_vtable.pl begin/
+	}
 
-	print $indent . "mg_type\n";
+	print "\n", $indent . "mg_type\n";
 	printf $format, @header;
 	printf $format, map {'-' x length $_} @header;
 	foreach (@rows) {
@@ -249,7 +255,13 @@ EOH
 	    printf $format, $type, $vtbl, $desc;
 	    printf $format, '', '', $_ foreach @cont;
 	}
-    }
+	print "\n";
+
+	while (<$oldguts>) {
+	    last if /^=for mg_vtable.pl end/;
+	}
+	do { print } while <$oldguts>;
+    })[0];
 }
 
 my @names = sort keys %sig;
@@ -342,3 +354,4 @@ print $vt "#define PL_vtbl_$_ PL_magic_vtables[want_vtbl_$_]\n"
 die "Too many vtable names" if @vtable_names > 63;
 
 read_only_bottom_close_and_rename($_) foreach $vt, $raw, $names;
+		 close_and_rename($guts);