[lldb][NFC] Remove ThreadSafeSTLVector and ThreadSafeSTLMap and their use in ValueObjectSynthetic

Summary:
ThreadSafeSTLVector and ThreadSafeSTLMap are not useful for achieving any degree of thread safety in LLDB
and should be removed before they are used in more places. They are only used (unsurprisingly incorrectly) in
`ValueObjectSynthetic::GetChildAtIndex`, so this patch replaces their use there with a simple mutex with which
we guard the related data structures. This doesn't make ValueObjectSynthetic::GetChildAtIndex
any more thread-safe, but on the other hand it at least allows us to get rid of the ThreadSafeSTL* data structures
without changing the observable behaviour of ValueObjectSynthetic (beside that it is now a few bytes smaller).

Reviewers: labath, JDevlieghere, jingham

Reviewed By: labath

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D70845

1 files changed, 38 insertions, 11 deletions

diff --git a/lldb/source/Core/ValueObjectSyntheticFilter.cpp b/lldb/source/Core/ValueObjectSyntheticFilter.cpp
index a6bf35eac70..a30be1b0833 100644
--- a/lldb/source/Core/ValueObjectSyntheticFilter.cpp
+++ b/lldb/source/Core/ValueObjectSyntheticFilter.cpp
@@ -48,8 +48,9 @@ public:
 ValueObjectSynthetic::ValueObjectSynthetic(ValueObject &parent,
                                            lldb::SyntheticChildrenSP filter)
     : ValueObject(parent), m_synth_sp(filter), m_children_byindex(),
-      m_name_toindex(), m_synthetic_children_count(UINT32_MAX),
-      m_synthetic_children_cache(), m_parent_type_name(parent.GetTypeName()),
+      m_name_toindex(), m_synthetic_children_cache(),
+      m_synthetic_children_count(UINT32_MAX),
+      m_parent_type_name(parent.GetTypeName()),
       m_might_have_children(eLazyBoolCalculate),
       m_provides_value(eLazyBoolCalculate) {
   SetName(parent.GetName());
@@ -177,14 +178,20 @@ bool ValueObjectSynthetic::UpdateValue() {
               "filter said caches are stale - clearing",
               GetName().AsCString());
     // filter said that cached values are stale
-    m_children_byindex.Clear();
-    m_name_toindex.Clear();
+    {
+      std::lock_guard<std::mutex> guard(m_child_mutex);
+      m_children_byindex.clear();
+      m_name_toindex.clear();
+    }
     // usually, an object's value can change but this does not alter its
     // children count for a synthetic VO that might indeed happen, so we need
     // to tell the upper echelons that they need to come back to us asking for
     // children
     m_children_count_valid = false;
-    m_synthetic_children_cache.Clear();
+    {
+      std::lock_guard<std::mutex> guard(m_child_mutex);
+      m_synthetic_children_cache.clear();
+    }
     m_synthetic_children_count = UINT32_MAX;
     m_might_have_children = eLazyBoolCalculate;
   } else {
@@ -232,7 +239,16 @@ lldb::ValueObjectSP ValueObjectSynthetic::GetChildAtIndex(size_t idx,
   UpdateValueIfNeeded();
 
   ValueObject *valobj;
-  if (!m_children_byindex.GetValueForKey(idx, valobj)) {
+  bool child_is_cached;
+  {
+    std::lock_guard<std::mutex> guard(m_child_mutex);
+    auto cached_child_it = m_children_byindex.find(idx);
+    child_is_cached = cached_child_it != m_children_byindex.end();
+    if (child_is_cached)
+      valobj = cached_child_it->second;
+  }
+
+  if (!child_is_cached) {
     if (can_create && m_synth_filter_up != nullptr) {
       LLDB_LOGF(log,
                 "[ValueObjectSynthetic::GetChildAtIndex] name=%s, child at "
@@ -254,9 +270,12 @@ lldb::ValueObjectSP ValueObjectSynthetic::GetChildAtIndex(size_t idx,
       if (!synth_guy)
         return synth_guy;
 
-      if (synth_guy->IsSyntheticChildrenGenerated())
-        m_synthetic_children_cache.AppendObject(synth_guy);
-      m_children_byindex.SetValueForKey(idx, synth_guy.get());
+      {
+        std::lock_guard<std::mutex> guard(m_child_mutex);
+        if (synth_guy->IsSyntheticChildrenGenerated())
+          m_synthetic_children_cache.push_back(synth_guy);
+        m_children_byindex[idx] = synth_guy.get();
+      }
       synth_guy->SetPreferredDisplayLanguageIfNeeded(
           GetPreferredDisplayLanguage());
       return synth_guy;
@@ -297,13 +316,21 @@ size_t ValueObjectSynthetic::GetIndexOfChildWithName(ConstString name) {
   UpdateValueIfNeeded();
 
   uint32_t found_index = UINT32_MAX;
-  bool did_find = m_name_toindex.GetValueForKey(name.GetCString(), found_index);
+  bool did_find;
+  {
+    std::lock_guard<std::mutex> guard(m_child_mutex);
+    auto name_to_index = m_name_toindex.find(name.GetCString());
+    did_find = name_to_index != m_name_toindex.end();
+    if (did_find)
+      found_index = name_to_index->second;
+  }
 
   if (!did_find && m_synth_filter_up != nullptr) {
     uint32_t index = m_synth_filter_up->GetIndexOfChildWithName(name);
     if (index == UINT32_MAX)
       return index;
-    m_name_toindex.SetValueForKey(name.GetCString(), index);
+    std::lock_guard<std::mutex> guard(m_child_mutex);
+    m_name_toindex[name.GetCString()] = index;
     return index;
   } else if (!did_find && m_synth_filter_up == nullptr)
     return UINT32_MAX;