perl5db.pl: apply the "break on first line" fix to b postpone subname

and just plain fix "b postpone subname", which didn't stop at all
on my postponed sub test code at all as far back at 5.10.

Fixes #799

Author: tonycoz

lib/perl5db.pl

@@ -6273,13 +6273,23 @@ sub postponed_sub {
 
         # find_sub's value is 'fullpath-filename:start-stop'. It's
         # possible that the filename might have colons in it too.
-        my ( $file, $i ) = ( find_sub($subname) =~ /^(.*):(\d+)-.*$/ );
+        my ($file, $i);
+        local $\ = '';
+        if ( $offset =~ /^\+?0$/) {
+            ( $file, $i ) = eval { subroutine_first_breakable_line($subname) }
+              or print $OUT $@;
+        }
+        else {
+            if (( $file, $i ) = ( find_sub($subname) =~ /^(.*):(\d+)-.*$/ )) {
+                # We got the start line. Add the offset '+<n>' from
+                # $postponed{subname}.
+                $i += $offset;
+            }
+            else {
+                print $OUT "Subroutine $subname not found.\n";
+            }
+        }
         if ($i) {
-
-            # We got the start line. Add the offset '+<n>' from
-            # $postponed{subname}.
-            $i += $offset;
-
             # Switch to the file this sub is in, temporarily.
             local *dbline = $main::{ '_<' . $file };
 
@@ -6298,13 +6308,9 @@ sub postponed_sub {
 
             # Copy the breakpoint in and delete it from %postponed.
             $dbline{$i} = delete $postponed{$subname};
-        } ## end if ($i)
 
-        # find_sub didn't find the sub.
-        else {
-            local $\ = '';
-            print $OUT "Subroutine $subname not found.\n";
-        }
+            _set_breakpoint_enabled_status($file, $i, 1);
+        } ## end if ($i)
         return;
     } ## end if ($postponed{$subname...
     elsif ( $postponed{$subname} eq 'compile' ) { $signal = 1 }

lib/perl5db.t

@@ -3565,6 +3565,43 @@ EOS
     $wrapper->contents_like(qr/Cannot break on XSUB B::svref_2object/, "can't break on XSUB");
 }
 
+{
+    my $wrapper = DebugWrap->new(
+        {
+            cmds =>
+            [
+                "b problem", # should fail
+                "b postpone problem",
+                "L",
+                "c",
+                "q"
+            ],
+            prog => \<<'EOS'
+print "1\n";
+eval <<'EOC';
+sub problem {
+    $SIG{__DIE__} = sub {
+        die "<b problem> will set a break point here.\n";
+    };    # The break point _should_ be set here.
+    warn "This line will run even if you enter <c problem>.\n";
+}
+EOC
+print "2\n";
+problem();
+print "3\n";
+EOS
+        }
+    );
+    $wrapper->contents_like(qr/Subroutine main::problem not found/,
+                            "problem not defined yet");
+    $wrapper->contents_like(qr/Postponed\ breakpoints\ in\ subroutines:
+                               \s+main::problem\s+break\s\+0\sif\s1/x,
+                            "check postponed breakpoint present");
+    $wrapper->contents_like(qr/The break point _should_/, "break at right place (c)");
+    $wrapper->output_unlike(qr/This line will run even if you enter <c problem>\./,
+                            "didn't run the wrong code");
+}
+
 done_testing();
 
 END {