[Lldb-commits] [PATCH] D117383: [lldb] From unordered_map synthetic provider, return std::pair children

[Dave Lee via Phabricator via lldb-commits]

kastiglione created this revision.
kastiglione added a reviewer: jingham.
kastiglione requested review of this revision.
Herald added a project: LLDB.
Herald added a subscriber: lldb-commits.

Change the behavior of the libc++ `unordered_map` synthetic provider to present
children as `std::pair` values, just like `std::map` does.

The synthetic provider for libc++ `std::unordered_map` has returned children
that expose a level of internal structure (over top of the key/value pair). For
example, given an unordered map initialized with `{{1,2}, {3, 4}}`, the output
is:

  (std::unordered_map<int, int, std::hash<int>, std::equal_to<int>, std::allocator<std::pair<const int, int> > >) map = size=2 {
    [0] = {
      __cc = (first = 3, second = 4)
    }
    [1] = {
      __cc = (first = 1, second = 2)
    }
  }

It's not ideal/necessary to have the numbered children embdedded in the `__cc`
field.

Note: the numbered children have type
`std::__hash_node<std::__hash_value_type<Key, T>, void *>::__node_value_type`,
and the `__cc` fields have type `std::__hash_value_type<Key, T>::value_type`.

Compare this output to `std::map`:

  (std::map<int, int, std::less<int>, std::allocator<std::pair<const int, int> > >) map = size=2 {
    [0] = (first = 1, second = 2)
    [1] = (first = 3, second = 4)

Where the numbered children have type `std::pair<const Key, T>`.

This changes the behavior of the synthetic provider for `unordered_map` to also
present children as `pairs`, just like `std::map`.

It appears the synthetic provider implementation for `unordered_map` was meant
to provide this behavior, but was maybe incomplete (see
d22a94377f7554a7e9df050f6dfc3ee42384e3fe). It has both an `m_node_type` and an
`m_element_type`, but uses only the former. The latter is exactly the type
needed for the children pairs. With this existing code, it's not much of a
change to make this work.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117383

Files:
  lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
  lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py


Index: lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py
===================================================================
--- lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py
+++ lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py
@@ -48,12 +48,17 @@
             "corrupt_map", ['%s::unordered_map' %
                     ns, 'size=0 {}'])
 
+        must_not_contain__cc = r'(?s)^(?!.*\b__cc = )'
+
         self.look_for_content_and_continue(
-            "map", ['%s::unordered_map' %
-                    ns, 'size=5 {', 'hello', 'world', 'this', 'is', 'me'])
+            "map", ['%s::unordered_map' % ns,
+                    must_not_contain__cc,
+                    'size=5 {', 'hello', 'world', 'this', 'is', 'me'])
 
         self.look_for_content_and_continue(
-            "mmap", ['%s::unordered_multimap' % ns, 'size=6 {', 'first = 3', 'second = "this"',
+            "mmap", ['%s::unordered_multimap' % ns,
+                     must_not_contain__cc,
+                     'size=6 {', 'first = 3', 'second = "this"',
                      'first = 2', 'second = "hello"'])
 
         self.look_for_content_and_continue(
Index: lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
===================================================================
--- lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
+++ lldb/source/Plugins/Language/CPlusPlus/LibCxxUnorderedMap.cpp
@@ -118,10 +118,16 @@
         m_element_type = m_element_type.GetPointeeType();
         m_node_type = m_element_type;
         m_element_type = m_element_type.GetTypeTemplateArgument(0);
-        std::string name;
-        m_element_type =
-            m_element_type.GetFieldAtIndex(0, name, nullptr, nullptr, nullptr);
-        m_element_type = m_element_type.GetTypedefedType();
+        if (m_element_type.GetNumFields() > 0) {
+	  // Check for - and use - the underlying key/value container type used
+	  // within std::unordered_map.
+          std::string name;
+          auto key_value_type =
+              m_element_type.GetFieldAtIndex(0, name, nullptr, nullptr, nullptr);
+          // __cc is a field of __hash_value_type, which is a typedef.
+          if (name == "__cc")
+            m_element_type = key_value_type.GetTypedefedType();
+        }
       }
       if (!m_node_type)
         return nullptr;
@@ -153,7 +159,7 @@
   ExecutionContext exe_ctx = val_hash.first->GetExecutionContextRef().Lock(
       thread_and_frame_only_if_stopped);
   return CreateValueObjectFromData(stream.GetString(), data, exe_ctx,
-                                   val_hash.first->GetCompilerType());
+                                   m_element_type);
 }
 
 bool lldb_private::formatters::LibcxxStdUnorderedMapSyntheticFrontEnd::


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