Make const redef warnings default in newXS

There is no reason why constant redefinition warnings should be
default warnings for sub foo(){1}, but not for newCONSTSUB (which
calls newXS, which triggers the warning).

To make this work properly, I also had to import sv.c’s ‘are these
const subs from the same SV originally?’ logic.  Constants created
with XS can have NULL for the SV (they return an empty list or
&PL_sv_undef), which means sv.c’s logic will stop *this=\&that from
warning if both this and that are such XS-created constants.
newCONSTSUB needed to be consistent with that.  It required tweaking a
test I added a few commits ago, which arguably shouldn’t have warned
the way it was written.

As of this commit (and before it, too, come to think of it),
newXS_len_flags’s calling convention is quite awful and would need to
be throughly re-thunk before being made into an API, or probably sim-
ply never made into an API.

2 files changed, 36 insertions, 11 deletions

diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index 46cc458d52..4f84c60d3e 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -1878,11 +1878,12 @@ call_method(methname, flags, ...)
 	PUSHs(sv_2mortal(newSViv(i)));
 
 void
-newCONSTSUB_type(stash, name, flags, type)
+newCONSTSUB_type(stash, name, flags, type, sv)
     HV* stash
     SV* name
     I32 flags
     int type
+    SV* sv
     PREINIT:
 	CV* cv;
 	STRLEN len;
@@ -1890,10 +1891,12 @@ newCONSTSUB_type(stash, name, flags, type)
     PPCODE:
         switch (type) {
            case 0:
-	       cv = newCONSTSUB(stash, pv, NULL);
+	       cv = newCONSTSUB(stash, pv, SvOK(sv) ? sv : NULL);
                break;
            case 1:
-               cv = newCONSTSUB_flags(stash, pv, len, flags | SvUTF8(name), NULL);
+               cv = newCONSTSUB_flags(
+                 stash, pv, len, flags | SvUTF8(name), SvOK(sv) ? sv : NULL
+               );
                break;
         }
         EXTEND(SP, 2);
diff --git a/ext/XS-APItest/t/newCONSTSUB.t b/ext/XS-APItest/t/newCONSTSUB.t
index b6e672d986..afd44262da 100644
--- a/ext/XS-APItest/t/newCONSTSUB.t
+++ b/ext/XS-APItest/t/newCONSTSUB.t
@@ -1,24 +1,46 @@
 #!perl
 
 use strict;
-use warnings;
 use utf8;
 use open qw( :utf8 :std );
-use Test::More tests => 11;
+use Test::More tests => 14;
 
 use XS::APItest;
 
-my ($const, $glob) = XS::APItest::newCONSTSUB_type(\%::, "sanity_check", 0, 0);
+# This test must happen outside of any warnings scope
+{
+ local $^W;
+ my $w;
+ local $SIG{__WARN__} = sub { $w .= shift };
+ sub frimple() { 78 }
+ newCONSTSUB_type(\%::, "frimple", 0, 1, undef);
+ like $w, qr/Constant subroutine frimple redefined at /,
+   'newCONSTSUB constant redefinition warning is unaffected by $^W=0';
+ undef $w;
+ newCONSTSUB_type(\%::, "frimple", 0, 1, undef);
+ is $w, undef, '...unless the const SVs are the same';
+ eval 'sub frimple() { 78 }';
+ undef $w;
+ newCONSTSUB_type(\%::, "frimple", 0, 1, "78");
+ is $w, undef, '...or the const SVs have the same value';
+}
+
+use warnings;
+
+my ($const, $glob) =
+ XS::APItest::newCONSTSUB_type(\%::, "sanity_check", 0, 0, undef);
 
 ok $const;
 ok *{$glob}{CODE};
 
-($const, $glob) = XS::APItest::newCONSTSUB_type(\%::, "\x{30cb}", 0, 0);
+($const, $glob) =
+  XS::APItest::newCONSTSUB_type(\%::, "\x{30cb}", 0, 0, undef);
 ok $const, "newCONSTSUB generates the constant,";
 ok *{$glob}{CODE}, "..and the glob,";
 ok !$::{"\x{30cb}"}, "...but not the right one";
 
-($const, $glob) = XS::APItest::newCONSTSUB_type(\%::, "\x{30cd}", 0, 1);
+($const, $glob) =
+  XS::APItest::newCONSTSUB_type(\%::, "\x{30cd}", 0, 1, undef);
 ok $const, "newCONSTSUB_flags generates the constant,";
 ok *{$glob}{CODE}, "..and the glob,";
 ok $::{"\x{30cd}"}, "...the right one!";
@@ -29,7 +51,7 @@ eval q{
   my $w;
   local $SIG{__WARN__} = sub { $w .= shift };
   *foo = sub(){123};
-  newCONSTSUB_type(\%::, "foo", 0, 1);
+  newCONSTSUB_type(\%::, "foo", 0, 1, undef);
   is $w, undef, 'newCONSTSUB uses calling scope for redefinition warnings';
  }
 };
@@ -39,11 +61,11 @@ eval q{
  *{"foo::\x{100}"} = sub(){return 123};
  my $w;
  local $SIG{__WARN__} = sub { $w .= shift };
- newCONSTSUB_type(\%foo::, "\x{100}", 0, 1);
+ newCONSTSUB_type(\%foo::, "\x{100}", 0, 1, undef);
  like $w, qr/Subroutine \x{100} redefined at /,
    'newCONSTSUB redefinition warning + utf8';
  undef $w;
- newCONSTSUB_type(\%foo::, "\x{100}", 0, 1);
+ newCONSTSUB_type(\%foo::, "\x{100}", 0, 1, 54);
  like $w, qr/Constant subroutine \x{100} redefined at /,
    'newCONSTSUB constant redefinition warning + utf8';
 }