[lldb] Unconditionally increment depth when printing children

[augusto2112]

Summary

The target.max-children-depth setting and --depth flag would be
ignored if treating pointer as arrays, fix that by always incrementing
the current depth when printing a new child.

[augusto2112]

Add radar

[aprantl]

Is ity possible to test this with a nested C++ type?

[kastiglione]

+1 to a test

thanks for the fix!

lldb/source/DataFormatters/ValueObjectPrinter.cpp

593

seems this is now used with m_omit_summary_depth, maybe name it consumed_summary_depth?

[augusto2112]

Add test

[kastiglione]

thanks!

[aprantl]

lldb/source/DataFormatters/ValueObjectPrinter.cpp

610

I would probably factor out:

if (does_consume_ptr_depth)
   --curr_ptr_depth;

lldb/test/API/lang/cpp/frame-var-depth-and-elem-count/main.cpp

16

Setting a breakpoint on the return is risky because there may not be any code associated with it. Something like

int puts(const char *s);

puts("break here");

is safer.

[augusto2112]

Addressed comments

lldb/include/lldb/DataFormatters/DumpValueObjectOptions.h

 namespace lldb_private {
 
 class DumpValueObjectOptions {
 public:
   struct PointerDepth {
     enum class Mode { Always, Default, Never } m_mode;
     uint32_t m_count;
 
-    PointerDepth operator--() const {
+    PointerDepth Decremented() const {
       if (m_count > 0)
         return PointerDepth{m_mode, m_count - 1};
       return PointerDepth{m_mode, m_count};
     }
 
     bool CanAllowExpansion() const;
   };
 

lldb/source/DataFormatters/ValueObjectPrinter.cpp

if (m_options.m_flat_output) {
     }
     m_stream->IndentMore();
   }
 }
 
 void ValueObjectPrinter::PrintChild(
     ValueObjectSP child_sp,
     const DumpValueObjectOptions::PointerDepth &curr_ptr_depth) {
-  const uint32_t consumed_depth = (!m_options.m_pointer_as_array) ? 1 : 0;
+  const uint32_t consumed_summary_depth = m_options.m_pointer_as_array ? 0 : 1;
   const bool does_consume_ptr_depth =
       ((IsPtr() && !m_options.m_pointer_as_array) || IsRef());
 
   DumpValueObjectOptions child_options(m_options);
   child_options.SetFormat(m_options.m_format)
       .SetSummary()
       .SetRootValueObjectName();
   child_options.SetScopeChecked(true)
       .SetHideName(m_options.m_hide_name)
       .SetHideValue(m_options.m_hide_value)
       .SetOmitSummaryDepth(child_options.m_omit_summary_depth > 1
                                ? child_options.m_omit_summary_depth -
-                                     consumed_depth
+                                     consumed_summary_depth
                                : 0)
       .SetElementCount(0);
 
   if (child_sp.get()) {
-    ValueObjectPrinter child_printer(
-        child_sp.get(), m_stream, child_options,
-        does_consume_ptr_depth ? --curr_ptr_depth : curr_ptr_depth,
-        m_curr_depth + consumed_depth, m_printed_instance_pointers);
+    auto ptr_depth = curr_ptr_depth;
+    if (does_consume_ptr_depth)
+      ptr_depth = curr_ptr_depth.Decremented();
+
+    ValueObjectPrinter child_printer(child_sp.get(), m_stream, child_options,
+                                     ptr_depth, m_curr_depth + 1,
+                                     m_printed_instance_pointers);
     child_printer.PrintValueObject();
   }
 }
 
 uint32_t ValueObjectPrinter::GetMaxNumChildrenToPrint(bool &print_dotdotdot) {
   ValueObject *synth_m_valobj = GetValueObjectForChildrenGeneration();
 
   if (m_options.m_pointer_as_array)

lldb/test/API/lang/cpp/frame-var-depth-and-elem-count/Makefile

+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/test/API/lang/cpp/frame-var-depth-and-elem-count/TestFrameVarDepthAndElemCount.py

+"""
+Tests that frame variable --depth and --element-count options work correctly
+together
+"""
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestFrameVarDepthAndElemCount(TestBase):
+    def test(self):
+        """Test that bool types work in the expression parser"""
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self, "// break here", lldb.SBFileSpec("main.cpp")
+        )
+
+        # Check that we print 5 elements but only 2 levels deep.
+        self.expect('frame var --depth 2 --element-count 5 -- c', 
+        substrs=[
+            '[0] = {\n    b ={...}\n  }',
+            '[1] = {\n    b ={...}\n  }',
+            '[2] = {\n    b ={...}\n  }',
+            '[3] = {\n    b ={...}\n  }',
+            '[4] = {\n    b ={...}\n  }',
+            ])
+

lldb/test/API/lang/cpp/frame-var-depth-and-elem-count/main.cpp

+#include <cstdio>
+
+struct A {
+  int i = 42;
+};
+
+struct B {
+  A a;
+};
+
+struct C {
+  B b;
+};
+
+int main() {
+  C *c = new C[5];
+  puts("break here");
+  return 0; // break here
+}