Hash values must be folded by the length of the buckets array. The length of
the buckets array is a discriminant of the container type, which means that it
is possible for the user to specify 0 as the length value. Insert must
therefore check for this case specifically, in order to prevent divide-by-zero
errors that would otherwise occur during computation of the bucket index for a
given key.
Tested on x86_64-pc-linux-gnu, committed on trunk
2011-08-31 Matthew Heaney <hea...@adacore.com>
* a-cbhama.adb, a-cbhase.adb (Insert): Check for zero-length buckets
array.
Index: a-cbhama.adb
===================================================================
--- a-cbhama.adb (revision 178358)
+++ a-cbhama.adb (working copy)
@@ -513,6 +513,11 @@
procedure Assign_Key (Node : in out Node_Type) is
begin
Node.Key := Key;
+
+ -- Note that we do not also assign the element component of the node
+ -- here, because this version of Insert does not accept an element
+ -- parameter.
+
-- Node.Element := New_Item;
end Assign_Key;
@@ -530,20 +535,17 @@
-- Start of processing for Insert
begin
- -- ???
- -- if HT_Ops.Capacity (HT) = 0 then
- -- HT_Ops.Reserve_Capacity (HT, 1);
- -- end if;
+ -- The buckets array length is specified by the user as a discriminant
+ -- of the container type, so it is possible for the buckets array to
+ -- have a length of zero. We must check for this case specifically, in
+ -- order to prevent divide-by-zero errors later, when we compute the
+ -- buckets array index value for a key, given its hash value.
- Local_Insert (Container, Key, Position.Node, Inserted);
+ if Container.Buckets'Length = 0 then
+ raise Capacity_Error with "No capacity for insertion";
+ end if;
- -- ???
- -- if Inserted
- -- and then HT.Length > HT_Ops.Capacity (HT)
- -- then
- -- HT_Ops.Reserve_Capacity (HT, HT.Length);
- -- end if;
-
+ Local_Insert (Container, Key, Position.Node, Inserted);
Position.Container := Container'Unchecked_Access;
end Insert;
@@ -590,20 +592,17 @@
-- Start of processing for Insert
begin
- -- ??
- -- if HT_Ops.Capacity (HT) = 0 then
- -- HT_Ops.Reserve_Capacity (HT, 1);
- -- end if;
+ -- The buckets array length is specified by the user as a discriminant
+ -- of the container type, so it is possible for the buckets array to
+ -- have a length of zero. We must check for this case specifically, in
+ -- order to prevent divide-by-zero errors later, when we compute the
+ -- buckets array index value for a key, given its hash value.
- Local_Insert (Container, Key, Position.Node, Inserted);
+ if Container.Buckets'Length = 0 then
+ raise Capacity_Error with "No capacity for insertion";
+ end if;
- -- ???
- -- if Inserted
- -- and then HT.Length > HT_Ops.Capacity (HT)
- -- then
- -- HT_Ops.Reserve_Capacity (HT, HT.Length);
- -- end if;
-
+ Local_Insert (Container, Key, Position.Node, Inserted);
Position.Container := Container'Unchecked_Access;
end Insert;
Index: a-cbhase.adb
===================================================================
--- a-cbhase.adb (revision 178358)
+++ a-cbhase.adb (working copy)
@@ -710,19 +710,17 @@
-- Start of processing for Insert
begin
- -- ???
- -- if HT_Ops.Capacity (HT) = 0 then
- -- HT_Ops.Reserve_Capacity (HT, 1);
- -- end if;
+ -- The buckets array length is specified by the user as a discriminant
+ -- of the container type, so it is possible for the buckets array to
+ -- have a length of zero. We must check for this case specifically, in
+ -- order to prevent divide-by-zero errors later, when we compute the
+ -- buckets array index value for an element, given its hash value.
- Local_Insert (Container, New_Item, Node, Inserted);
+ if Container.Buckets'Length = 0 then
+ raise Capacity_Error with "No capacity for insertion";
+ end if;
- -- ???
- -- if Inserted
- -- and then HT.Length > HT_Ops.Capacity (HT)
- -- then
- -- HT_Ops.Reserve_Capacity (HT, HT.Length);
- -- end if;
+ Local_Insert (Container, New_Item, Node, Inserted);
end Insert;
------------------
