avoid warnings from shmread() when given undefined variable

(from Tom Christiansen)

p4raw-id: //depot/perl@5504

1 files changed, 3 insertions, 0 deletions

diff --git a/doio.c b/doio.c
index d818185c48..d0a770461e 100644
--- a/doio.c
+++ b/doio.c
@@ -1849,6 +1849,9 @@ Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
     if (shm == (char *)-1)	/* I hate System V IPC, I really do */
 	return -1;
     if (optype == OP_SHMREAD) {
+	/* suppress warning when reading into undef var (tchrist 3/Mar/00) */
+	if (! SvOK(mstr))
+	    sv_setpvn(mstr, "", 0);
 	SvPV_force(mstr, len);
 	mbuf = SvGROW(mstr, msize+1);