[perl #57512] Warnings for implicitly closed handles

If the implicit close() fails, warn about it, mentioning $! in the
message.  This is a default warning in the io category.

We do this in two spots, sv_clear and gp_free.  While sv_clear would
be sufficient to get the warning emitted, the warning won’t contain
the name of the handle when called from there, because lone IO thing-
ies are nameless.  Doing it also when a GV’s glob pointer is freed--as
long as the IO thingy in there has a reference count of 1--allows the
name to be included in the message, because we still have the glob,
which is where the name is stored.

The result:

$ ./miniperl -Ilib -e 'open fh, ">/Volumes/Disk Image/foo"; print fh "x"x1000, "\n" for 1..50; undef *fh'
Warning: unable to close filehandle fh properly: No space left on device at -e line 1.

1 files changed, 10 insertions, 0 deletions

diff --git a/gv.c b/gv.c
index 7abc6ccacb..c8d434544c 100644
--- a/gv.c
+++ b/gv.c
@@ -2515,6 +2515,16 @@ Perl_gp_free(pTHX_ GV *gv)
            (void)hv_deletehek(PL_stashcache, hvname_hek, G_DISCARD);
 	SvREFCNT_dec(hv);
       }
+      if (io && SvREFCNT(io) == 1 && IoIFP(io)
+	     && (IoTYPE(io) == IoTYPE_WRONLY ||
+		 IoTYPE(io) == IoTYPE_RDWR   ||
+		 IoTYPE(io) == IoTYPE_APPEND)
+	     && ckWARN_d(WARN_IO)
+	     && IoIFP(io) != PerlIO_stdin()
+	     && IoIFP(io) != PerlIO_stdout()
+	     && IoIFP(io) != PerlIO_stderr()
+	     && !(IoFLAGS(io) & IOf_FAKE_DIRP))
+	io_close(io, gv, FALSE, TRUE);
       SvREFCNT_dec(io);
       SvREFCNT_dec(cv);
       SvREFCNT_dec(form);