plperl: Correctly handle empty arrays in plperl_ref_from_pg_array.

plperl_ref_from_pg_array() didn't consider the case that postgrs arrays
can have 0 dimensions (when they're empty) and accessed the first
dimension without a check. Fix that by special casing the empty array
case.

Author: Alex Hunsaker
Reported-By: Andres Freund / valgrind / buildfarm animal skink
Discussion: 20160308063240.usnzg6bsbjrne667@alap3.anarazel.de
Backpatch: 9.1-

diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index b35ef3f64bcd504404800df84ad427a3a849dc67..cd917ab8e46ddc13a293144184a3f45e71cab01c 100644 (file)
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1450,17 +1450,25 @@ plperl_ref_from_pg_array(Datum arg, Oid typid)
    info->ndims = ARR_NDIM(ar);
    dims = ARR_DIMS(ar);
 
-   deconstruct_array(ar, elementtype, typlen, typbyval,
-                     typalign, &info->elements, &info->nulls,
-                     &nitems);
+   /* No dimensions? Return an empty array */
+   if (info->ndims == 0)
+   {
+       av = newRV_noinc((SV *) newAV());
+   }
+   else
+   {
+       deconstruct_array(ar, elementtype, typlen, typbyval,
+                         typalign, &info->elements, &info->nulls,
+                         &nitems);
 
-   /* Get total number of elements in each dimension */
-   info->nelems = palloc(sizeof(int) * info->ndims);
-   info->nelems[0] = nitems;
-   for (i = 1; i < info->ndims; i++)
-       info->nelems[i] = info->nelems[i - 1] / dims[i - 1];
+       /* Get total number of elements in each dimension */
+       info->nelems = palloc(sizeof(int) * info->ndims);
+       info->nelems[0] = nitems;
+       for (i = 1; i < info->ndims; i++)
+           info->nelems[i] = info->nelems[i - 1] / dims[i - 1];
 
-   av = split_array(info, 0, nitems, 0);
+       av = split_array(info, 0, nitems, 0);
+   }
 
    hv = newHV();
    (void) hv_store(hv, "array", 5, av, 0);
@@ -1479,6 +1487,9 @@ split_array(plperl_array_info *info, int first, int last, int nest)
    int         i;
    AV         *result;
 
+   /* we should only be called when we have something to split */
+   Assert(info->ndims > 0);
+
    /* since this function recurses, it could be driven to stack overflow */
    check_stack_depth();