BTreeMap: improve gdb introspection of BTreeMap with ZST keys or values

Author: ssomers

library/alloc/src/collections/btree/node.rs

@@ -87,7 +87,6 @@ impl<K, V> LeafNode<K, V> {
 #[repr(C)]
 // gdb_providers.py uses this type name for introspection.
 struct InternalNode<K, V> {
-    // gdb_providers.py uses this field name for introspection.
     data: LeafNode<K, V>,
 
     /// The pointers to the children of this node. `len + 1` of these are considered

src/etc/gdb_providers.py

@@ -229,8 +229,8 @@ def cast_to_internal(node):
                 yield child
         if i < length:
             # Avoid "Cannot perform pointer math on incomplete type" on zero-sized arrays.
-            key = keys[i]["value"]["value"] if keys.type.sizeof > 0 else None
-            val = vals[i]["value"]["value"] if vals.type.sizeof > 0 else None
+            key = keys[i]["value"]["value"] if keys.type.sizeof > 0 else "()"
+            val = vals[i]["value"]["value"] if vals.type.sizeof > 0 else "()"
             yield key, val
 
 
@@ -242,11 +242,8 @@ def children_of_map(map):
             root = root.cast(gdb.lookup_type(root.type.name[21:-1]))
         boxed_root_node = root["node"]
         height = root["height"]
-        for i, (key, val) in enumerate(children_of_node(boxed_root_node, height)):
-            if key is not None:
-                yield "key{}".format(i), key
-            if val is not None:
-                yield "val{}".format(i), val
+        for child in children_of_node(boxed_root_node, height):
+            yield child
 
 
 class StdBTreeSetProvider:
@@ -258,8 +255,8 @@ def to_string(self):
 
     def children(self):
         inner_map = self.valobj["map"]
-        for child in children_of_map(inner_map):
-            yield child
+        for i, (child, _) in enumerate(children_of_map(inner_map)):
+            yield "[{}]".format(i), child
 
     @staticmethod
     def display_hint():
@@ -274,8 +271,9 @@ def to_string(self):
         return "BTreeMap(size={})".format(self.valobj["length"])
 
     def children(self):
-        for child in children_of_map(self.valobj):
-            yield child
+        for i, (key, val) in enumerate(children_of_map(self.valobj)):
+            yield "key{}".format(i), key
+            yield "val{}".format(i), val
 
     @staticmethod
     def display_hint():

src/test/debuginfo/pretty-std-collections.rs

@@ -34,20 +34,26 @@
 // gdb-check:$6 = BTreeMap(size=15) = {[0] = pretty_std_collections::MyLeafNode (0), [...]}
 // (abbreviated because it's boring but we need enough elements to include internal nodes)
 
-// gdb-command: print zst_btree_map
-// gdb-check:$7 = BTreeMap(size=1)
+// gdb-command: print zst_key_btree_map
+// gdb-check:$7 = BTreeMap(size=1) = {[()] = 1}
+
+// gdb-command: print zst_val_btree_map
+// gdb-check:$8 = BTreeMap(size=1) = {[1] = ()}
+
+// gdb-command: print zst_key_val_btree_map
+// gdb-check:$9 = BTreeMap(size=1) = {[()] = ()}
 
 // gdb-command: print vec_deque
-// gdb-check:$8 = VecDeque(size=3) = {5, 3, 7}
+// gdb-check:$10 = VecDeque(size=3) = {5, 3, 7}
 
 // gdb-command: print vec_deque2
-// gdb-check:$9 = VecDeque(size=7) = {2, 3, 4, 5, 6, 7, 8}
+// gdb-check:$11 = VecDeque(size=7) = {2, 3, 4, 5, 6, 7, 8}
 
 // gdb-command: print hash_map
-// gdb-check:$10 = HashMap(size=4) = {[1] = 10, [2] = 20, [3] = 30, [4] = 40}
+// gdb-check:$12 = HashMap(size=4) = {[1] = 10, [2] = 20, [3] = 30, [4] = 40}
 
 // gdb-command: print hash_set
-// gdb-check:$11 = HashSet(size=4) = {1, 2, 3, 4}
+// gdb-check:$13 = HashSet(size=4) = {1, 2, 3, 4}
 
 // === LLDB TESTS ==================================================================================
 
@@ -114,8 +120,14 @@ fn main() {
         nasty_btree_map.insert(i, MyLeafNode(i));
     }
 
-    let mut zst_btree_map: BTreeMap<(), ()> = BTreeMap::new();
-    zst_btree_map.insert((), ());
+    let mut zst_key_btree_map: BTreeMap<(), i32> = BTreeMap::new();
+    zst_key_btree_map.insert((), 1);
+
+    let mut zst_val_btree_map: BTreeMap<i32, ()> = BTreeMap::new();
+    zst_val_btree_map.insert(1, ());
+
+    let mut zst_key_val_btree_map: BTreeMap<(), ()> = BTreeMap::new();
+    zst_key_val_btree_map.insert((), ());
 
     // VecDeque
     let mut vec_deque = VecDeque::new();