Fix memory leaks in mro_package_moved

This commit adds a new HV_FETCH_EMPTY_HE flag for hv_common. It is to
be used in conjunction with HV_FETCH_LVALUE. It just stops the newly-
created HE from having a new undef scalar assigned to it.

This allows code to call hv_common just once instead of an hv_exists/
hv_store pair.

It was such a double hv_common call that I was trying to avoid with
HV_FETCH_LVALUE, without realising that it was leaking.

3 files changed, 5 insertions, 4 deletions

diff --git a/hv.c b/hv.c
index da8d76421d..bc1d4f9eba 100644
--- a/hv.c
+++ b/hv.c
@@ -735,7 +735,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	return NULL;
     }
     if (action & HV_FETCH_LVALUE) {
-	val = newSV(0);
+	val = action & HV_FETCH_EMPTY_HE ? NULL : newSV(0);
 	if (SvMAGICAL(hv)) {
 	    /* At this point the old hv_fetch code would call to hv_store,
 	       which in turn might do some tied magic. So we need to make that
diff --git a/hv.h b/hv.h
index 81a4d89beb..33ecef5d0f 100644
--- a/hv.h
+++ b/hv.h
@@ -590,6 +590,7 @@ a string/length pair, and no precomputed hash.
 #define HV_FETCH_LVALUE		0x10
 #define HV_FETCH_JUST_SV	0x20
 #define HV_DELETE		0x40
+#define HV_FETCH_EMPTY_HE	0x80 /* Leave HeVAL null. */
 
 /*
 =for apidoc newHV
diff --git a/mro.c b/mro.c
index 47f99e4129..750699415f 100644
--- a/mro.c
+++ b/mro.c
@@ -831,7 +831,7 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV *stash, HV *oldstash,
 	 = (HE *)
 	     hv_common(
 	      stashes, NULL, (const char *)&oldstash, sizeof(HV *), 0,
-	      HV_FETCH_LVALUE, NULL, 0
+	      HV_FETCH_LVALUE|HV_FETCH_EMPTY_HE, NULL, 0
 	     );
 	if(HeVAL(entry) == (SV *)oldstash) {
 	    oldstash = NULL;
@@ -887,7 +887,7 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV *stash, HV *oldstash,
 	 = (HE *)
 	     hv_common(
 	      stashes, NULL, (const char *)&stash, sizeof(HV *), 0,
-	      HV_FETCH_LVALUE, NULL, 0
+	      HV_FETCH_LVALUE|HV_FETCH_EMPTY_HE, NULL, 0
 	     );
 	if(HeVAL(entry) == &PL_sv_yes || HeVAL(entry) == (SV *)stash)
 	    stash = NULL;
@@ -918,7 +918,7 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV *stash, HV *oldstash,
 	     = (HE *)
 	         hv_common(
 	          stashes, NULL, (const char *)&revstash, sizeof(HV *), 0,
-	          HV_FETCH_LVALUE, NULL, 0
+	          HV_FETCH_LVALUE|HV_FETCH_EMPTY_HE, NULL, 0
 	         );
 	    HeVAL(entry) = (SV *)revstash;