(perl #127380) add tests for -Di

MANIFEST

@@ -5627,6 +5627,7 @@ t/run/switcha.t			Test the -a switch
 t/run/switchC.t			Test the -C switch
 t/run/switchd-78586.t		See whether bug 78586 is fixed
 t/run/switchd.t			Test the -d switch
+t/run/switchDx.t		Test the -D switch
 t/run/switches.t		Tests for the other switches (-0, -l, -c, -s, -M, -m, -V, -v, -h, -z, -i)
 t/run/switchF1.t		Pathological tests for the -F switch
 t/run/switchF2.t		Pathological tests for the -F switch

t/run/switchDx.t

@@ -0,0 +1,39 @@
+#!./perl -w
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require './test.pl';
+    skip_all_if_miniperl();
+}
+
+use Config;
+
+my $perlio_log = "perlio$$.txt";
+
+skip_all "DEBUGGING build required"
+  unless $::Config{ccflags} =~ /DEBUGGING/
+         or $^O eq 'VMS' && $::Config{usedebugging_perl} eq 'Y';
+
+plan tests => 6;
+
+END {
+    unlink $perlio_log;
+}
+{
+    unlink $perlio_log;
+    local $ENV{PERLIO_DEBUG} = $perlio_log;
+    fresh_perl_is("print qq(hello\n)", "hello\n",
+                  { stderr => 1 },
+                  "No perlio debug file without -Di...");
+    ok(!-e $perlio_log, "...no perlio.txt found");
+    fresh_perl_is("print qq(hello\n)", "\nEXECUTING...\n\nhello\n",
+                  { stderr => 1, switches => [ "-Di" ] },
+                  "Perlio debug file with both -Di and PERLIO_DEBUG...");
+    ok(-e $perlio_log, "... perlio debugging file found with -Di and PERLIO_DEBUG");
+
+    unlink $perlio_log;
+    fresh_perl_is("print qq(hello\n)", "\nEXECUTING...\n\nhello\n",
+                  { stderr => 1, switches => [ "-TDi" ] },
+                  "No perlio debug file with -T..");
+    ok(!-e $perlio_log, "...no perlio debugging file found");
+}