Fix RT26188, speed up keys() on empty hash

diff --git a/hv.c b/hv.c
index 3322848..5f233d6 100644 (file)
--- a/hv.c
+++ b/hv.c
@@ -2143,26 +2143,32 @@ Perl_hv_iternext_flags(pTHX_ HV *hv, I32 flags)
             }
        }
     }
-    while (!entry) {
-       /* OK. Come to the end of the current list.  Grab the next one.  */
 
-       iter->xhv_riter++; /* HvRITER(hv)++ */
-       if (iter->xhv_riter > (I32)xhv->xhv_max /* HvRITER(hv) > HvMAX(hv) */) {
-           /* There is no next one.  End of the hash.  */
-           iter->xhv_riter = -1; /* HvRITER(hv) = -1 */
-           break;
-       }
-       entry = (HvARRAY(hv))[iter->xhv_riter];
+    /* Quick bailout if the hash is empty anyway.
+       I don't know if placeholders are included in the KEYS count, so a defensive check
+    */
+    if (HvKEYS(hv) || (flags & HV_ITERNEXT_WANTPLACEHOLDERS)) {
+       while (!entry) {
+           /* OK. Come to the end of the current list.  Grab the next one.  */
+
+           iter->xhv_riter++; /* HvRITER(hv)++ */
+           if (iter->xhv_riter > (I32)xhv->xhv_max /* HvRITER(hv) > HvMAX(hv) */) {
+               /* There is no next one.  End of the hash.  */
+               iter->xhv_riter = -1; /* HvRITER(hv) = -1 */
+               break;
+           }
+           entry = (HvARRAY(hv))[iter->xhv_riter];
 
-        if (!(flags & HV_ITERNEXT_WANTPLACEHOLDERS)) {
-            /* If we have an entry, but it's a placeholder, don't count it.
-              Try the next.  */
-           while (entry && HeVAL(entry) == &PL_sv_placeholder)
-               entry = HeNEXT(entry);
+           if (!(flags & HV_ITERNEXT_WANTPLACEHOLDERS)) {
+               /* If we have an entry, but it's a placeholder, don't count it.
+                  Try the next.  */
+               while (entry && HeVAL(entry) == &PL_sv_placeholder)
+                   entry = HeNEXT(entry);
+           }
+           /* Will loop again if this linked list starts NULL
+              (for HV_ITERNEXT_WANTPLACEHOLDERS)
+              or if we run through it and find only placeholders.  */
        }
-       /* Will loop again if this linked list starts NULL
-          (for HV_ITERNEXT_WANTPLACEHOLDERS)
-          or if we run through it and find only placeholders.  */
     }
 
     if (oldentry && HvLAZYDEL(hv)) {           /* was deleted earlier? */