Rollup merge of #77788 - ssomers:btree_cleanup_gdb, r=Mark-Simulacrum

BTreeMap: fix gdb provider on BTreeMap with ZST keys or values

Avoid error when gdb is asked to inspect a BTreeMap or BTreeSet with a zero-sized type as key or value. And clean up.

r? @Mark-Simulacrum

src/etc/gdb_providers.py

@@ -207,30 +207,46 @@ class StdRefCellProvider:
         yield "borrow", self.borrow
 
 
-# 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", 1)
+        internal_type_name = node.type.target().name.replace("LeafNode", "InternalNode", 1)
         internal_type = 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()
+    leaf = node_ptr.dereference()
     keys = leaf["keys"]
-    values = leaf["vals"]
+    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 None
+            val = vals[i]["value"]["value"] if vals.type.sizeof > 0 else None
+            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 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
 
 
 class StdBTreeSetProvider:
@@ -242,15 +258,8 @@ class StdBTreeSetProvider:
 
     def children(self):
         inner_map = self.valobj["map"]
-        if inner_map["length"] > 0:
-            root = inner_map["root"]
-            if "core::option::Option<" in root.type.name:
-                type_name = str(root.type.name).replace("core::option::Option<", "", 1)[:-1]
-                root = root.cast(gdb.lookup_type(type_name))
-
-            node_ptr = root["node"]
-            for i, child in enumerate(children_of_node(node_ptr, root["height"], False)):
-                yield "[{}]".format(i), child
+        for child in children_of_map(inner_map):
+            yield child
 
     @staticmethod
     def display_hint():
@@ -265,16 +274,8 @@ class StdBTreeMapProvider:
         return "BTreeMap(size={})".format(self.valobj["length"])
 
     def children(self):
-        if self.valobj["length"] > 0:
-            root = self.valobj["root"]
-            if "core::option::Option<" in root.type.name:
-                type_name = str(root.type.name).replace("core::option::Option<", "", 1)[:-1]
-                root = root.cast(gdb.lookup_type(type_name))
-
-            node_ptr = root["node"]
-            for i, child in enumerate(children_of_node(node_ptr, root["height"], True)):
-                yield "key{}".format(i), child[0]
-                yield "val{}".format(i), child[1]
+        for child in children_of_map(self.valobj):
+            yield child
 
     @staticmethod
     def display_hint():

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

@@ -34,17 +34,20 @@
 // 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 vec_deque
-// gdb-check:$7 = VecDeque(size=3) = {5, 3, 7}
+// gdb-check:$8 = VecDeque(size=3) = {5, 3, 7}
 
 // gdb-command: print vec_deque2
-// gdb-check:$8 = VecDeque(size=7) = {2, 3, 4, 5, 6, 7, 8}
+// gdb-check:$9 = VecDeque(size=7) = {2, 3, 4, 5, 6, 7, 8}
 
 // gdb-command: print hash_map
-// gdb-check:$9 = HashMap(size=4) = {[1] = 10, [2] = 20, [3] = 30, [4] = 40}
+// gdb-check:$10 = HashMap(size=4) = {[1] = 10, [2] = 20, [3] = 30, [4] = 40}
 
 // gdb-command: print hash_set
-// gdb-check:$10 = HashSet(size=4) = {1, 2, 3, 4}
+// gdb-check:$11 = HashSet(size=4) = {1, 2, 3, 4}
 
 // === LLDB TESTS ==================================================================================
 
@@ -69,9 +72,9 @@
 #![allow(unused_variables)]
 use std::collections::BTreeMap;
 use std::collections::BTreeSet;
-use std::collections::VecDeque;
 use std::collections::HashMap;
 use std::collections::HashSet;
+use std::collections::VecDeque;
 use std::hash::{BuildHasherDefault, Hasher};
 
 struct MyLeafNode(i32); // helps to ensure we don't blindly replace substring "LeafNode"
@@ -111,6 +114,9 @@ fn main() {
         nasty_btree_map.insert(i, MyLeafNode(i));
     }
 
+    let mut zst_btree_map: BTreeMap<(), ()> = BTreeMap::new();
+    zst_btree_map.insert((), ());
+
     // VecDeque
     let mut vec_deque = VecDeque::new();
     vec_deque.push_back(5);