Don't hide frame of entry point into libc++

Author: vogelsgesang

lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp

@@ -79,9 +79,22 @@ class LibCXXFrameRecognizer : public StackFrameRecognizer {
     if (!sc.function)
       return {};
 
+    // Check if we have a regex match
+    bool matches_regex = false; 
     for (RegularExpression &r : m_hidden_regex)
-      if (r.Execute(sc.function->GetNameNoArguments()))
+      if (r.Execute(sc.function->GetNameNoArguments())) {
+         matches_regex = true;
+         break;
+      }
+
+    if (matches_regex) {
+      // Only hide this frame if the immediate caller is also within libc++.
+      lldb::StackFrameSP parent_frame = frame_sp->GetThread()->GetStackFrameAtIndex(frame_sp->GetFrameIndex() + 1);
+      const auto& parent_sc = parent_frame->GetSymbolContext(lldb::eSymbolContextFunction);
+      if (parent_sc.function->GetNameNoArguments().GetStringRef().starts_with("std::")) {
         return m_hidden_frame;
+      }
+    }
 
     return {};
   }

lldb/test/API/lang/cpp/libcxx-internals-recognizer/TestLibcxxInternalsRecognizer.py

@@ -17,10 +17,10 @@ def test_frame_recognizer(self):
 
         expected_parents = {
             "sort_less(int, int)": ["::sort", "test_algorithms"],
-            # `std::ranges::sort` is implemented as an object of types `__sort`,
-            # which unfortunately means that there is no `std::ranges::sort`
-            # stack frame, and `main` is the direct parent of `my_less_ranges`.
-            "ranges_sort_less(int, int)": ["test_algorithms"],
+            # `std::ranges::sort` is implemented as an object of types `__sort`.
+            # We never hide the frame of the entry-point into the standard library, even
+            # if the name starts with `__` which usually indicates an internal function.
+            "ranges_sort_less(int, int)": ["ranges::__sort::operator()", "test_algorithms"],
             # `ranges::views::transform` internally uses `std::invoke`, and that
             # call also shows up in the stack trace
             "view_transform(int)": ["::invoke", "ranges::transform_view", "test_algorithms"],