DBG: Update BTreeMap/BTreeSet GDB pretty-printers

* Fixes #5722
* Handle zero-sized keys or values rust-lang/rust#77788

Author: artemmukhin

prettyPrinters/gdb_providers.py

@@ -1,7 +1,6 @@
 from sys import version_info
 
 import gdb
-from gdb import lookup_type
 
 if version_info[0] >= 3:
     xrange = range
@@ -222,30 +221,43 @@ def to_string(self):
         return self.value
 
 
-# Yield each key (and optionally value) from a BoxedNode.
-def children_of_node(boxed_node, height, want_values):
+# Yields children (in a provider's sense of the word) for a tree headed by a BoxedNode.
+# In particular, yields each key/value pair in the node and in any child nodes.
+def children_of_node(boxed_node, height):
     def cast_to_internal(node):
-        internal_type_name = str(node.type.target()).replace('LeafNode', 'InternalNode')
-        internal_type = lookup_type(internal_type_name)
+        internal_type_name = node.type.target().name.replace("LeafNode", "InternalNode", 1)
+        internal_type = gdb.lookup_type(internal_type_name)
         return node.cast(internal_type.pointer())
 
-    node_ptr = unwrap_unique_or_non_null(boxed_node['ptr'])
-    node_ptr = cast_to_internal(node_ptr) if height > 0 else node_ptr
-    leaf = node_ptr['data'] if height > 0 else node_ptr.dereference()
-    keys = leaf['keys']
-    values = leaf['vals']
-    length = int(leaf['len'])
+    node_ptr = unwrap_unique_or_non_null(boxed_node["ptr"])
+    leaf = node_ptr.dereference()
+    keys = leaf["keys"]
+    vals = leaf["vals"]
+    edges = cast_to_internal(node_ptr)["edges"] if height > 0 else None
+    length = int(leaf["len"])
 
     for i in xrange(0, length + 1):
         if height > 0:
-            child_ptr = node_ptr['edges'][i]['value']['value']
-            for child in children_of_node(child_ptr, height - 1, want_values):
+            boxed_child_node = edges[i]["value"]["value"]
+            for child in children_of_node(boxed_child_node, height - 1):
                 yield child
         if i < length:
-            if want_values:
-                yield (keys[i]['value']['value'], values[i]['value']['value'])
-            else:
-                yield keys[i]['value']['value']
+            # Avoid "Cannot perform pointer math on incomplete type" on zero-sized arrays.
+            key = keys[i]["value"]["value"] if keys.type.sizeof > 0 else gdb.parse_and_eval("()")
+            val = vals[i]["value"]["value"] if vals.type.sizeof > 0 else gdb.parse_and_eval("()")
+            yield key, val
+
+
+# Yields children for a BTreeMap.
+def children_of_map(map):
+    if map["length"] > 0:
+        root = map["root"]
+        if root.type.name.startswith("core::option::Option<"):
+            root = root.cast(gdb.lookup_type(root.type.name[21:-1]))
+        boxed_root_node = root["node"]
+        height = root["height"]
+        for child in children_of_node(boxed_root_node, height):
+            yield child
 
 
 class StdBTreeSetProvider:
@@ -256,9 +268,8 @@ def to_string(self):
         return "size={}".format(self.valobj["map"]["length"])
 
     def children(self):
-        root = self.valobj["map"]["root"]
-        node_ptr = root["node"]
-        for i, child in enumerate(children_of_node(node_ptr, root["height"], want_values=False)):
+        inner_map = self.valobj["map"]
+        for i, (child, _) in enumerate(children_of_map(inner_map)):
             yield ("[{}]".format(i), child)
 
     @staticmethod
@@ -274,13 +285,9 @@ def to_string(self):
         return "size={}".format(self.valobj["length"])
 
     def children(self):
-        root = self.valobj["root"]
-        node_ptr = root["node"]
-        i = 0
-        for child in children_of_node(node_ptr, root["height"], want_values=True):
-            yield ("key{}".format(i), child[0])
-            yield ("val{}".format(i), child[1])
-            i = i + 1
+        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():

pretty_printers_tests/tests/btree.rs

@@ -1,5 +1,4 @@
 // min-version: 1.33.0
-// max-version: 1.43.0
 
 // === GDB TESTS ===================================================================================
 
@@ -11,6 +10,8 @@
 // gdb-command: print btree_map
 // gdbg-check:$2 = size=15 = {[0] = 0, [1] = 1, [2] = 2, [3] = 3, [4] = 4, [5] = 5, [6] = 6, [7] = 7, [8] = 8, [9] = 9, [10] = 10, [11] = 11, [12] = 12, [13] = 13, [14] = 14}
 
+// gdb-command: print zst_btree_map
+// gdbg-check:$3 = size=1 = {[()] = ()}
 
 use std::collections::{BTreeMap, BTreeSet};
 
@@ -24,5 +25,9 @@ fn main() {
     for i in 0..15 {
         btree_map.insert(i, i);
     }
+
+    let mut zst_btree_map: BTreeMap<(), ()> = BTreeMap::new();
+    zst_btree_map.insert((), ());
+
     print!(""); // #break
 }