odb: avoid segfault in insert_buffer and makeNewName when base name is null

src/odb/src/db/dbBlock.cpp

@@ -3841,6 +3841,7 @@ std::string _dbBlock::makeNewName(
                    parent->getHierarchicalName(),
                    block->getHierarchyDelimiter());
   }
+  assert(base_name != nullptr);
   buf.append(fmt::string_view(base_name));
   buf.push_back('\0');  // Null-terminate for find* functions
 
@@ -3984,6 +3985,7 @@ std::string dbBlock::makeNewInstName(dbModInst* parent,
 
 const char* dbBlock::getBaseName(const char* full_name) const
 {
+  assert(full_name != nullptr);
   const char hierarchy_delimiter = getHierarchyDelimiter();
   const char* base_name = full_name;
   size_t backslash_run = 0;

src/odb/src/db/dbInsertBuffer.cpp

@@ -104,8 +104,12 @@ dbInst* dbInsertBuffer::insertBufferSimple(dbObject* term_obj,
                        ? static_cast<dbITerm*>(term_obj)->getInst()->getModule()
                        : nullptr;
   buffer_master_ = buffer_master;
-  new_buf_base_name_ = new_buf_base_name;
-  new_net_base_name_ = new_net_base_name;
+  new_buf_base_name_ = (new_buf_base_name && new_buf_base_name[0] != '\0')
+                           ? new_buf_base_name
+                           : kDefaultBufBaseName;
+  new_net_base_name_ = (new_net_base_name && new_net_base_name[0] != '\0')
+                           ? new_net_base_name
+                           : kDefaultNetBaseName;
   uniquify_ = uniquify;
 
   // Store original driver pin before buffer insertion modifies net structure
@@ -161,8 +165,12 @@ dbInst* dbInsertBuffer::insertBufferBeforeLoads(
   resetMembers();
 
   buffer_master_ = buffer_master;
-  new_buf_base_name_ = new_buf_base_name;
-  new_net_base_name_ = new_net_base_name;
+  new_buf_base_name_ = (new_buf_base_name && new_buf_base_name[0] != '\0')
+                           ? new_buf_base_name
+                           : kDefaultBufBaseName;
+  new_net_base_name_ = (new_net_base_name && new_net_base_name[0] != '\0')
+                           ? new_net_base_name
+                           : kDefaultNetBaseName;
   uniquify_ = uniquify;
 
   if (loc == nullptr) {

src/odb/test/cpp/TestInsertBuffer.cpp

@@ -105,5 +105,46 @@ INSTANTIATE_TEST_SUITE_P(FlatAndHierarchical,
                                           testing::Bool(),
                                           testing::Bool()));
 
+TEST(TestInsertBufferNullName, HandlesNullBaseNamesWithoutCrash)
+{
+  tst::LoadedDesign design(
+      tst::Technology::kNangate45,
+      tst::getRunfilePath("_main/src/odb/test/cpp/insert_buffer_port_alias.v"),
+      "top",
+      false);
+  auto* block = design.getBlock();
+  auto* p = block->findBTerm("p");
+  ASSERT_NE(p, nullptr);
+  auto* original_net = p->getNet();
+  ASSERT_NE(original_net, nullptr);
+  auto* buffer_master = design.getDb()->findMaster("BUF_X1");
+  ASSERT_NE(buffer_master, nullptr);
+
+  const Point location{20000, 10000};
+  PtrSet<dbObject> loads{p};
+
+  // Exercises the fix for issue #12016: passing nullptr for base names
+  // must fall back to default names ("buf", "net") rather than crashing
+  // in _dbBlock::makeNewName.
+  auto* buffer = original_net->insertBufferBeforeLoads(
+      loads, buffer_master, &location, nullptr, nullptr);
+  ASSERT_NE(buffer, nullptr);
+  EXPECT_FALSE(buffer->getName().empty());
+
+  auto* ld = block->findInst("ld");
+  ASSERT_NE(ld, nullptr);
+  auto* load_pin = ld->findITerm("A");
+  ASSERT_NE(load_pin, nullptr);
+  auto* ld_net = load_pin->getNet();
+  ASSERT_NE(ld_net, nullptr);
+
+  // Exercises insertBufferBeforeLoad (single-load path) with nullptr base
+  // names.
+  auto* single_buffer = ld_net->insertBufferBeforeLoad(
+      load_pin, buffer_master, &location, nullptr, nullptr);
+  ASSERT_NE(single_buffer, nullptr);
+  EXPECT_FALSE(single_buffer->getName().empty());
+}
+
 }  // namespace
 }  // namespace odb