Rollup merge of rust-lang#140130 - ede1998:add-lldb-btree-providers, r=Mark-Simulacrum

Add LLDB providers for BTreeMap and BTreeSet

Fixes rust-lang#111868.

I'm unsure what the supported LLDB versions for `rust-lldb` are. I tested with LLDB 18 and 19 and it works with those but I know that it does not work with LLDB 14 which was picked by my `codelldb` extension for some reason (even though it packages LLDB 19).

I also had to work around what seems like an LLDB bug to me. Otherwise, I'd have kept the code more similar to the GDB provider.
`SBTarget.FindFirstType()` does not find the types that I'm searching for (`LeafNode<i32, i32>*`):

```
target = node.GetTarget()
print("leaf type:", node.GetType())
internal_type = target.FindFirstType(node.GetType().GetName())
print("Actual type:", internal_type)
```

which prints

```
leaf type: struct alloc::collections::btree::node::LeafNode<int, int> *
Actual type: No value
```

All in all, my experience with LLDB debug provider was very fiddly/they seem to break easily but I think it would be better to have `BTreeMap`/`BTreeSet` providers than not have them.

Getting to run the `debuginfo` tests was a pain too because of rust-lang#126092 and errors with `import _lldb` (rust-lang#123621).
I ended up re-compling lldb from source against python 3.10 because the tests don't work if lldb is compiled against python 3.12.

Also, it seems like the tests are not run in CI? At least I had a test commit in the PR before to trigger a `debuginfo` test failure which I didn't see here in my PR.

Author: compiler-errors

src/etc/lldb_lookup.py

@@ -42,6 +42,11 @@ def summary_lookup(valobj: lldb.SBValue, _dict: LLDBOpaque) -> str:
     if rust_type == RustType.STD_HASH_SET:
         return SizeSummaryProvider(valobj, _dict)
 
+    if rust_type == RustType.STD_BTREE_MAP:
+        return SizeSummaryProvider(valobj, _dict)
+    if rust_type == RustType.STD_BTREE_SET:
+        return SizeSummaryProvider(valobj, _dict)
+
     if rust_type == RustType.STD_RC:
         return StdRcSummaryProvider(valobj, _dict)
     if rust_type == RustType.STD_ARC:
@@ -105,6 +110,12 @@ def synthetic_lookup(valobj: lldb.SBValue, _dict: LLDBOpaque) -> object:
         else:
             return StdOldHashMapSyntheticProvider(hash_map, _dict, show_values=False)
 
+    if rust_type == RustType.STD_BTREE_MAP:
+        return StdBTreeMapSyntheticProvider(valobj, _dict)
+    if rust_type == RustType.STD_BTREE_SET:
+        btree_map = valobj.GetChildAtIndex(0)
+        return StdBTreeMapSyntheticProvider(btree_map, _dict, show_values=False)
+
     if rust_type == RustType.STD_RC:
         return StdRcSyntheticProvider(valobj, _dict)
     if rust_type == RustType.STD_ARC:

src/etc/lldb_providers.py

@@ -1151,6 +1151,130 @@ def has_children(self) -> bool:
         return True
 
 
+def children_of_node(node_ptr: SBValue, height: int):
+    def get_edges(node: SBValue) -> SBValue:
+        # BTreeMap implementation does ad-hoc polymorphism between LeafNode and InternalNode
+        # with raw pointers.
+        # https://github.com/rust-lang/rust/issues/90520#issuecomment-2211103129
+        # Implementing this the same way as the GDB provider with type casting fails
+        # because LLDB does not find the target type for some reason.
+        # Therefore, we manually do the pointer arithmetic to get the edges array
+        # and handle it as raw pointers later instead of MaybeUninit<NonNull<LeafNode<K,V>>>.
+        # We can do that because InternalNode is repr(C).
+        leaf_ptr_type = node.GetType()
+        # Array has a constant length of 2 * B
+        edges_arr_type = leaf_ptr_type.GetArrayType(12)
+        node_addr = node.unsigned
+        leaf_size = leaf_ptr_type.GetPointeeType().size
+        edges_addr = node_addr + leaf_size
+        return node.CreateValueFromAddress("edges", edges_addr, edges_arr_type)
+
+    def unwrap_item_from_array_of_maybe_uninit(arr: SBValue, index: int) -> SBValue:
+        element = arr.GetChildAtIndex(index)
+        return element.GetChildMemberWithName("value").GetChildMemberWithName("value")
+
+    if node_ptr.type.name.startswith("alloc::collections::btree::node::BoxedNode<"):
+        # BACKCOMPAT: rust 1.49
+        node_ptr = node_ptr.GetChildMemberWithName("ptr")
+
+    if not node_ptr.type.IsPointerType():
+        # After the first recursion, this method is called with a raw pointer type directly
+        # instead of NonNull<T>
+        node_ptr = unwrap_unique_or_non_null(node_ptr)
+
+    leaf = node_ptr.Dereference()
+    keys = leaf.GetChildMemberWithName("keys")
+    vals = leaf.GetChildMemberWithName("vals")
+    length = leaf.GetChildMemberWithName("len").unsigned
+    edges = get_edges(node_ptr) if height > 0 else None
+
+    for i in range(length + 1):
+        if height > 0:
+            child_ptr = edges.GetChildAtIndex(i)
+            yield from children_of_node(child_ptr, height - 1)
+        if i < length:
+            # Avoid "Cannot perform pointer math on incomplete type" on zero-sized arrays.
+            key_type_size = keys.type.size
+            val_type_size = vals.type.size
+            key = (
+                unwrap_item_from_array_of_maybe_uninit(keys, i)
+                if key_type_size > 0
+                else node_ptr.EvaluateExpression("()")
+            )
+            val = (
+                unwrap_item_from_array_of_maybe_uninit(vals, i)
+                if val_type_size > 0
+                else node_ptr.EvaluateExpression("()")
+            )
+            yield key, val
+
+
+class StdBTreeMapSyntheticProvider:
+    def __init__(self, valobj: SBValue, _dict: LLDBOpaque, show_values: bool = True):
+        self.valobj = valobj
+        self._dict = _dict
+        self.show_values = show_values
+
+    def num_children(self) -> int:
+        return self.size
+
+    def get_child_index(self, name: str) -> int:
+        index = name.lstrip("[").rstrip("]")
+        if index.isdigit():
+            return int(index)
+        else:
+            return -1
+
+    def get_child_at_index(self, index: int) -> SBValue:
+        key, value = self.items[index]
+        if self.show_values:
+            data = key.GetData()
+            assert data.Append(value.GetData()), "Failed to create key value pair"
+            return self.valobj.CreateValueFromData("[%s]" % index, data, self.pair_type)
+        return self.valobj.CreateValueFromData("[%s]" % index, key.GetData(), key.type)
+
+    def update(self) -> bool:
+        self.size = self.valobj.GetChildMemberWithName("length").unsigned
+        self.items = []
+
+        # Determine the type for the tuple (Key, Value)
+        # - get_template_args helper breaks on console because type is shown as
+        #   `core::marker::PhantomData<(&str, &str) *>`
+        # - Type lookup after get_template_args helper fails with codelldb for unclear reasons
+        # - Native `template_args[0]` from LLDB fails with codelldb and just says `T` if printed
+        #   on console
+        marker = self.valobj.GetChildMemberWithName("_marker")
+        marker_type = marker.GetType()
+        box = marker_type.GetTemplateArgumentType(0)
+        self.pair_type = box.GetPointeeType()
+
+        if self.size == 0:
+            return
+
+        root = self.valobj.GetChildMemberWithName("root")
+
+        if root.type.name.startswith("core::option::Option<"):
+            synthetic_children = root.children[0]
+            current_variant = synthetic_children.GetChildMemberWithName("$variant$")
+            root = current_variant.GetChildMemberWithName(
+                "value"
+            ).GetChildMemberWithName("__0")
+
+        height = root.GetChildMemberWithName("height")
+        node_ptr = root.GetChildMemberWithName("node")
+
+        self.items = [
+            (key, value) for key, value in children_of_node(node_ptr, height.unsigned)
+        ]
+
+        assert len(self.items) == self.size
+
+        return False
+
+    def has_children(self) -> bool:
+        return True
+
+
 def StdRcSummaryProvider(valobj: SBValue, _dict: LLDBOpaque) -> str:
     strong = valobj.GetChildMemberWithName("strong").GetValueAsUnsigned()
     weak = valobj.GetChildMemberWithName("weak").GetValueAsUnsigned()

src/tools/compiletest/src/runtest/debugger.rs

@@ -111,6 +111,9 @@ impl DebuggerCommands {
 }
 
 /// Check that the pattern in `check_line` applies to `line`. Returns `true` if they do match.
+/// Note that this matching is lazy, i.e. matches as little as possible and thus might leave
+/// stuff unparsed, failing the check.
+/// This is different to usual regex or global matching that is typically eager.
 fn check_single_line(line: &str, check_line: &str) -> bool {
     // Allow check lines to leave parts unspecified (e.g., uninitialized
     // bits in the  wrong case of an enum) with the notation "[...]".

tests/debuginfo/pretty-std-collections.rs

@@ -51,6 +51,33 @@
 
 // lldb-command:run
 
+// lldb-command: v btree_set
+// lldb-check:[...] 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 }
+
+// lldb-command: v empty_btree_set
+// lldb-check:[...] size=0
+
+// lldb-command: v btree_map
+// lldb-check:[...] size=15 { [0] = { 0 = 0 1 = 0 } [1] = { 0 = 1 1 = 1 } [2] = { 0 = 2 1 = 2 } [3] = { 0 = 3 1 = 3 } [4] = { 0 = 4 1 = 4 } [5] = { 0 = 5 1 = 5 } [6] = { 0 = 6 1 = 6 } [7] = { 0 = 7 1 = 7 } [8] = { 0 = 8 1 = 8 } [9] = { 0 = 9 1 = 9 } [10] = { 0 = 10 1 = 10 } [11] = { 0 = 11 1 = 11 } [12] = { 0 = 12 1 = 12 } [13] = { 0 = 13 1 = 13 } [14] = { 0 = 14 1 = 14 } }
+
+// lldb-command: v option_btree_map
+// lldb-check:[...] size=2 { [0] = { 0 = false 1 = [...] } [1] = { 0 = true 1 = [...]
+// (The matching here is lazy, so we cannot add braces at the end because they would match
+// intermediate braces and fail because not the entire input was consumed.)
+
+// lldb-command: v nasty_btree_map
+// lldb-check:[...] size=15 { [0] = { 0 = 0 1 = { 0 = 0 } } [1] = { 0 = 1 1 = { 0 = 1 } } [2] = { 0 = 2 1 = { 0 = 2 } } [3] = { 0 = 3 1 = { 0 = 3 } } [4] = { 0 = 4 1 = { 0 = 4 } } [5] = { 0 = 5 1 = { 0 = 5 } } [6] = { 0 = 6 1 = { 0 = 6 } } [7] = { 0 = 7 1 = { 0 = 7 } } [8] = { 0 = 8 1 = { 0 = 8 } } [9] = { 0 = 9 1 = { 0 = 9 } } [10] = { 0 = 10 1 = { 0 = 10 } } [11] = { 0 = 11 1 = { 0 = 11 } } [12] = { 0 = 12 1 = { 0 = 12 } } [13] = { 0 = 13 1 = { 0 = 13 } } [14] = { 0 = 14 1 = { 0 = 14 } } }
+// (Does not print out the type name in lldb)
+
+// lldb-command: v zst_key_btree_map
+// lldb-check:[...] size=1 { [0] = { 1 = 1 } }
+
+// lldb-command: v zst_val_btree_map
+// lldb-check:[...] size=1 { [0] = { 0 = 1 } }
+
+// lldb-command: v zst_key_val_btree_map
+// lldb-check:[...] size=1 { [0] = {} }
+
 // lldb-command:v vec_deque
 // lldb-check:[...] size=3 { [0] = 5 [1] = 3 [2] = 7 }