Expand $^O at build time when generating Config::_V()

Config::_V() is how perl -V is implemented internally, and is called called
directly from the interpreter's switch passing routine. Hence the value of
$^O at runtime will always be the same as the value of $^O at build time,
so conditionals dependent on the value of $^O will always take the same
execution path. So only generate the relevant code, and hence avoid shipping
VMS and Cygwin specific code except on those platforms. (But add a sanity
test in Config::_V() to ensure that the runtime $^O has the correct value -
ie that the Perl code and the perl binary correspond.)

1 files changed, 10 insertions, 9 deletions

diff --git a/configpm b/configpm
index ec81bfc8cf..6ea7419852 100755
--- a/configpm
+++ b/configpm
@@ -149,7 +149,10 @@ die "Can't automatically determine name for Config_heavy.pl from '$Config_PM'"
 my $config_txt;
 my $heavy_txt;
 
-$heavy_txt .= sprintf <<'ENDOFBEG';
+my $from = $^O eq 'VMS' ? 'PERLSHR image' : 'binary (from libperl)';
+my $env_cygwin = $^O eq 'cygwin'
+    ? 'push @env, "CYGWIN=\"$ENV{CYGWIN}\"" if $ENV{CYGWIN};' . "\n" : "";
+$heavy_txt .= sprintf <<'ENDOFBEG', $^O, $^O, $from, $^O, $env_cygwin;
 # This file was created by configpm when Perl was built. Any changes
 # made to this file will be lost the next time perl is built.
 
@@ -176,6 +179,9 @@ sub local_patches {
 }
 
 sub _V {
+    die "Perl lib was built for '%s' but is being run on '$^O'"
+        unless "%s" eq $^O;
+
     my ($bincompat, $non_bincompat, $date, @patches) = Internals::V();
 
     my $opts = join ' ', sort split ' ', "$bincompat $non_bincompat";
@@ -185,11 +191,7 @@ sub _V {
     $opts =~ s/(?=.{53})(.{1,53}) /$1\n                        /mg;
 
     print Config::myconfig();
-    if ($^O eq 'VMS') {
-        print "\nCharacteristics of this PERLSHR image: \n";
-    } else {
-        print "\nCharacteristics of this binary (from libperl): \n";
-    }
+    print "\nCharacteristics of this %s: \n";
 
     print "  Compile-time options: $opts\n";
 
@@ -198,13 +200,12 @@ sub _V {
         print "\t$_\n" foreach @patches;
     }
 
-    print "  Built under $^O\n";
+    print "  Built under %s\n";
 
     print "  $date\n" if defined $date;
 
     my @env = map { "$_=\"$ENV{$_}\"" } sort grep {/^PERL/} keys %%ENV;
-    push @env, "CYGWIN=\"$ENV{CYGWIN}\"" if $^O eq 'cygwin' and $ENV{CYGWIN};
-
+%s
     if (@env) {
         print "  \%%ENV:\n";
         print "    $_\n" foreach @env;