C++ Multiple Inheritance

bpftrace · Mar 28, 2024 · 651b120 · 651b120
1 parent 960ec3b
commit 651b120
Show file tree

Hide file tree

Showing 4 changed files with 79 additions and 13 deletions.
diff --git a/src/dwarf_parser.cpp b/src/dwarf_parser.cpp
@@ -196,30 +196,30 @@ SizedType Dwarf::get_stype(const std::string &type_name)
   return CreateNone();
 }
 
-void Dwarf::resolve_fields(std::shared_ptr<Struct> str, lldb::SBType type)
+void Dwarf::resolve_fields(std::shared_ptr<Struct> &str, lldb::SBType type, size_t offset)
 {
   if (!type.IsValid())
     return;
 
-  for (uint32_t i = 0; i < type.GetNumberOfVirtualBaseClasses(); i++) {
-    auto parent = type.GetVirtualBaseClassAtIndex(i);
-    resolve_fields(str, parent.GetType());
-  }
-
-  for (uint32_t i = 0; i < type.GetNumberOfDirectBaseClasses(); i++) {
-    auto parent = type.GetDirectBaseClassAtIndex(i);
-    resolve_fields(str, parent.GetType());
-  }
-
   for (uint32_t i = 0; i < type.GetNumberOfFields(); i++) {
     auto field = type.GetFieldAtIndex(i);
     auto field_type = get_stype(field.GetType());
     str->AddField(field.GetName() ?: "",
                   get_stype(field.GetType()),
-                  field.GetOffsetInBytes(),
+                  offset + field.GetOffsetInBytes(),
                   resolve_bitfield(field),
                   false);
   }
+
+  for (uint32_t i = 0; i < type.GetNumberOfVirtualBaseClasses(); i++) {
+    auto parent = type.GetVirtualBaseClassAtIndex(i);
+    resolve_fields(str, parent.GetType(), parent.GetOffsetInBytes());
+  }
+
+  for (uint32_t i = 0; i < type.GetNumberOfDirectBaseClasses(); i++) {
+    auto parent = type.GetDirectBaseClassAtIndex(i);
+    resolve_fields(str, parent.GetType(), parent.GetOffsetInBytes());
+  }
 }
 
 void Dwarf::resolve_fields(const SizedType &type)

diff --git a/src/dwarf_parser.h b/src/dwarf_parser.h
@@ -38,7 +38,7 @@ class Dwarf {
 
   std::string get_type_name(lldb::SBType type);
   SizedType get_stype(lldb::SBType type, bool resolve_structs = true);
-  void resolve_fields(std::shared_ptr<Struct> str, lldb::SBType type);
+  void resolve_fields(std::shared_ptr<Struct> &str, lldb::SBType type, size_t offset = 0);
   std::optional<Bitfield> resolve_bitfield(lldb::SBTypeMember field);
 
   BPFtrace *bpftrace_;

diff --git a/tests/data/data_source_cxx.cpp b/tests/data/data_source_cxx.cpp
@@ -26,6 +26,28 @@ class LittleChild : public Child {
   LittleChild(int a, int b, int c, int d, int e, int f, int g) : Child(a, b, c, d, e, f), g(g) {}
 };
 
+struct Top {
+  int x;
+};
+
+struct Left : public Top {
+  int y;
+};
+
+struct Right : public Top {
+  int z;
+};
+
+struct Bottom : public Left, public Right {
+  int w;
+};
+
+struct Multi : public Parent, public Top {
+  int abc;
+
+  Multi(int a, int b, int c, int d, int e) : Parent{a, b, c, d}, Top{e}, abc{e + 1} {}
+};
+
 int func_1(Child &c, Parent &p __attribute__((unused)))
 {
   return dynamic_cast<Parent&>(c).d;
@@ -36,6 +58,11 @@ int func_2(LittleChild &lc)
   return dynamic_cast<Parent&>(lc).d;
 }
 
+int func_3(Multi &m, Bottom &b __attribute__((unused)))
+{
+  return m.abc;
+}
+
 int main(void)
 {
   Parent p{1, 2, 3, 4};
@@ -45,5 +72,18 @@ int main(void)
   LittleChild lc{1, 2, 3, 4, 5, 6, 7};
   func_2(lc);
 
+  Multi m{1, 2, 3, 4, 5};
+  Bottom b{
+    {      // Left
+      {1}, // Left's Top
+      2    // Left's y
+    }, {   // Right
+      {3}, // Right's Top
+      4    // Right's z
+    },
+    5      // Bottom's w
+  };
+  func_3(m, b);
+
   return 0;
 }
diff --git a/tests/field_analyser.cpp b/tests/field_analyser.cpp
@@ -564,6 +564,32 @@ TEST_F(field_analyser_dwarf, parse_inheritance_chain)
   CheckLittleChildFields(cls);
 }
 
+TEST_F(field_analyser_dwarf, parse_inheritance_multi)
+{
+  BPFtrace bpftrace;
+  std::string uprobe = "uprobe:" + std::string(cxx_bin_);
+  test(bpftrace, uprobe + ":cpp:func_3 { $x = args.m->abc; }", 0);
+
+  ASSERT_TRUE(bpftrace.structs.Has("struct Multi"));
+  auto cls = bpftrace.structs.Lookup("struct Multi").lock();
+
+  ASSERT_TRUE(cls->HasFields());
+  ASSERT_EQ(cls->fields.size(), 6);
+  ASSERT_EQ(cls->size, 24);
+
+  CheckParentFields(cls);
+
+  EXPECT_TRUE(cls->HasField("x"));
+  EXPECT_TRUE(cls->GetField("x").type.IsIntTy());
+  EXPECT_EQ(cls->GetField("x").type.GetSize(), 4);
+  EXPECT_EQ(cls->GetField("x").offset, 16);
+
+  EXPECT_TRUE(cls->HasField("abc"));
+  EXPECT_TRUE(cls->GetField("abc").type.IsIntTy());
+  EXPECT_EQ(cls->GetField("abc").type.GetSize(), 4);
+  EXPECT_EQ(cls->GetField("abc").offset, 20);
+}
+
 TEST_F(field_analyser_dwarf, parse_struct_anonymous_fields)
 {
   GTEST_SKIP() << "Anonymous fields not supported #3084";