RobotLocomotion · rpoyner-tri · Jan 2, 2024 · Dec 30, 2023
diff --git a/lcm/drake_lcm.cc b/lcm/drake_lcm.cc
@@ -7,7 +7,6 @@
 #include <vector>
 
 #include <glib.h>
-#include <lcm/lcm-cpp.hpp>  // N.B. C++ is used only by get_lcm_instance().
 #include <lcm/lcm.h>
 
 #include "drake/common/drake_assert.h"
@@ -82,7 +81,6 @@ class DrakeLcm::Impl {
   std::string lcm_url_;
   bool deferred_initialization_{};
   lcm_t* lcm_{};
-  std::unique_ptr<::lcm::LCM> lcm_cpp_;  // Typically nullptr.
   const std::string channel_suffix_;
   std::vector<std::weak_ptr<DrakeSubscription>> subscriptions_;
   std::string handle_subscriptions_error_message_;
@@ -108,12 +106,8 @@ std::string DrakeLcm::get_lcm_url() const {
   return impl_->lcm_url_;
 }
 
-::lcm::LCM* DrakeLcm::get_native() {
-  if (impl_->lcm_cpp_ == nullptr) {
-    // Create the C++ wrapper only when requested by the user or our unit test.
-    impl_->lcm_cpp_ = std::make_unique<::lcm::LCM>(impl_->lcm_);
-  }
-  return impl_->lcm_cpp_.get();
+void* DrakeLcm::get_native_lcm_handle_for_unit_testing() {
+  return impl_->lcm_;
 }
 
 void DrakeLcm::Publish(const std::string& channel, const void* data,

diff --git a/lcm/drake_lcm.h b/lcm/drake_lcm.h
@@ -6,19 +6,9 @@
 #include <string_view>
 
 #include "drake/common/drake_copyable.h"
-#include "drake/common/drake_deprecated.h"
 #include "drake/lcm/drake_lcm_interface.h"
 #include "drake/lcm/drake_lcm_params.h"
 
-#ifndef DRAKE_DOXYGEN_CXX
-namespace lcm {
-// We don't want to pollute our Drake headers with the include paths for either
-// @lcm or @glib, so we forward-declare the `class ::lcm::LCM` for use only by
-// DrakeLcm::get_native() -- an unit-test-only private function.
-class LCM;
-}  // namespace lcm
-#endif
-
 namespace drake {
 namespace lcm {
 
@@ -54,16 +44,6 @@ class DrakeLcm : public DrakeLcmInterface {
    */
   ~DrakeLcm() override;
 
-  DRAKE_DEPRECATED(
-      "2024-01-01",
-      "Drake will no longer provide access to the underlying lcm::LCM object.")
-  /**
-   * (Advanced.) An accessor to the underlying LCM instance. The returned
-   * pointer is guaranteed to be valid for the duration of this object's
-   * lifetime.
-   */
-  ::lcm::LCM* get_lcm_instance() { return get_native(); }
-
   void Publish(const std::string&, const void*, int,
                std::optional<double>) override;
   std::string get_lcm_url() const override;
@@ -80,7 +60,7 @@ class DrakeLcm : public DrakeLcmInterface {
 
   void OnHandleSubscriptionsError(const std::string&) override;
 
-  ::lcm::LCM* get_native();
+  void* get_native_lcm_handle_for_unit_testing();
 
   class Impl;
   std::unique_ptr<Impl> impl_;

diff --git a/lcm/drake_lcm_log.cc b/lcm/drake_lcm_log.cc
@@ -7,7 +7,7 @@
 #include <utility>
 #include <vector>
 
-#include "lcm/lcm-cpp.hpp"
+#include "lcm/lcm.h"
 
 #include "drake/common/drake_assert.h"
 
@@ -22,8 +22,10 @@ class DrakeLcmLog::Impl {
  public:
   std::multimap<std::string, HandlerFunction> subscriptions_;
   std::vector<MultichannelHandlerFunction> multichannel_subscriptions_;
-  std::unique_ptr<::lcm::LogFile> log_;
-  const ::lcm::LogEvent* next_event_{nullptr};
+  std::unique_ptr<::lcm_eventlog_t, decltype(&::lcm_eventlog_destroy)>  // BR
+      log_{nullptr, &::lcm_eventlog_destroy};
+  std::unique_ptr<::lcm_eventlog_event_t, decltype(&::lcm_eventlog_free_event)>
+      next_event_{nullptr, &::lcm_eventlog_free_event};
 };
 
 DrakeLcmLog::DrakeLcmLog(const std::string& file_name, bool is_write,
@@ -34,12 +36,12 @@ DrakeLcmLog::DrakeLcmLog(const std::string& file_name, bool is_write,
       url_("lcmlog://" + file_name),
       impl_(new Impl) {
   if (is_write_) {
-    impl_->log_ = std::make_unique<::lcm::LogFile>(file_name, "w");
+    impl_->log_.reset(lcm_eventlog_create(file_name.c_str(), "w"));
   } else {
-    impl_->log_ = std::make_unique<::lcm::LogFile>(file_name, "r");
-    impl_->next_event_ = impl_->log_->readNextEvent();
+    impl_->log_.reset(lcm_eventlog_create(file_name.c_str(), "r"));
+    impl_->next_event_.reset(lcm_eventlog_read_next_event(impl_->log_.get()));
   }
-  if (!impl_->log_->good()) {
+  if (impl_->log_ == nullptr) {
     throw std::runtime_error("Failed to open log file: " + file_name);
   }
 }
@@ -56,20 +58,20 @@ void DrakeLcmLog::Publish(const std::string& channel, const void* data,
     throw std::logic_error("Publish is only available for log saving.");
   }
 
-  ::lcm::LogEvent log_event{};
+  ::lcm_eventlog_event_t log_event{};
   if (!overwrite_publish_time_with_system_clock_) {
     log_event.timestamp = second_to_timestamp(time_sec.value_or(0.0));
   } else {
     log_event.timestamp = std::chrono::steady_clock::now().time_since_epoch() /
                           std::chrono::microseconds(1);
   }
-  log_event.channel = channel;
+  log_event.channellen = channel.size();
+  log_event.channel = const_cast<char*>(channel.c_str());
   log_event.datalen = data_size;
   log_event.data = const_cast<void*>(data);
-
   std::lock_guard<std::mutex> lock(mutex_);
   // TODO(siyuan): should make cache this or thread write this.
-  if (impl_->log_->writeEvent(&log_event) != 0) {
+  if (::lcm_eventlog_write_event(impl_->log_.get(), &log_event) != 0) {
     throw std::runtime_error("Publish failed to write to log file.");
   }
 }
@@ -132,25 +134,26 @@ void DrakeLcmLog::DispatchMessageAndAdvanceLog(double current_time) {
   if (impl_->next_event_ == nullptr) {
     return;
   }
-  const ::lcm::LogEvent& next_event = *impl_->next_event_;
+  const ::lcm_eventlog_event_t& next_event = *impl_->next_event_;
 
   // Do nothing if the call time does not match the event's time.
   if (current_time != timestamp_to_second(next_event.timestamp)) {
     return;
   }
 
   // Dispatch message if necessary.
-  const auto& range = impl_->subscriptions_.equal_range(next_event.channel);
+  const std::string channel(next_event.channel, next_event.channellen);
+  const auto& range = impl_->subscriptions_.equal_range(channel);
   for (auto iter = range.first; iter != range.second; ++iter) {
     const HandlerFunction& handler = iter->second;
     handler(next_event.data, next_event.datalen);
   }
   for (const auto& multi_handler : impl_->multichannel_subscriptions_) {
-    multi_handler(next_event.channel, next_event.data, next_event.datalen);
+    multi_handler(channel, next_event.data, next_event.datalen);
   }
 
   // Advance log.
-  impl_->next_event_ = impl_->log_->readNextEvent();
+  impl_->next_event_.reset(lcm_eventlog_read_next_event(impl_->log_.get()));
 }
 
 void DrakeLcmLog::OnHandleSubscriptionsError(const std::string& error_message) {

diff --git a/lcm/test/drake_lcm_test.cc b/lcm/test/drake_lcm_test.cc
@@ -17,9 +17,10 @@ namespace lcm {
 class DrakeLcmTester {
  public:
   DrakeLcmTester() = delete;
-  static ::lcm::LCM* get_native(DrakeLcm* dut) {
+  static ::lcm::LCM get_native(DrakeLcm* dut) {
     DRAKE_DEMAND(dut != nullptr);
-    return dut->get_native();
+    return ::lcm::LCM(
+        static_cast<::lcm_t*>(dut->get_native_lcm_handle_for_unit_testing()));
   }
 };
 namespace {
@@ -59,7 +60,8 @@ class DrakeLcmTest : public ::testing::Test {
     EXPECT_TRUE(message_was_received);
   }
 
-  ::lcm::LCM* get_native() { return DrakeLcmTester::get_native(dut_.get()); }
+  // Returns a C++ interface wrapper around DrakeLcm's internal LCM object.
+  ::lcm::LCM get_native() { return DrakeLcmTester::get_native(dut_.get()); }
 
   // The device under test.
   std::unique_ptr<DrakeLcm> dut_ = std::make_unique<DrakeLcm>();
@@ -105,7 +107,7 @@ TEST_F(DrakeLcmTest, EmptyChannelTest) {
 // Tests DrakeLcm's ability to publish an LCM message.
 // We subscribe using the native LCM APIs.
 TEST_F(DrakeLcmTest, PublishTest) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.PublishTest";
 
   lcmt_drake_signal received{};
@@ -115,18 +117,18 @@ TEST_F(DrakeLcmTest, PublishTest) {
         DRAKE_DEMAND(new_value != nullptr);
         received = *new_value;
       };
-  native_lcm->subscribe(channel_name, std::move(handler));
+  native_lcm.subscribe(channel_name, std::move(handler));
 
   LoopUntilDone(&received, 20 /* retries */, [&]() {
     Publish(dut_.get(), channel_name, message_);
-    native_lcm->handleTimeout(50 /* millis */);
+    native_lcm.handleTimeout(50 /* millis */);
   });
 }
 
 // Tests DrakeLcm's ability to subscribe to an LCM message.
 // We publish using the native LCM APIs.
 TEST_F(DrakeLcmTest, SubscribeTest) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.SubscribeTest";
 
   lcmt_drake_signal received{};
@@ -138,15 +140,15 @@ TEST_F(DrakeLcmTest, SubscribeTest) {
 
   int total = 0;
   LoopUntilDone(&received, 20 /* retries */, [&]() {
-    native_lcm->publish(channel_name, &message_);
+    native_lcm.publish(channel_name, &message_);
     total += dut_->HandleSubscriptions(50 /* millis */);
   });
   EXPECT_EQ(total, 1);
 }
 
 // Repeats the above test, but with explicit opt-out of unsubscribe.
 TEST_F(DrakeLcmTest, SubscribeTest2) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.SubscribeTest2";
 
   lcmt_drake_signal received{};
@@ -159,15 +161,15 @@ TEST_F(DrakeLcmTest, SubscribeTest2) {
 
   int total = 0;
   LoopUntilDone(&received, 20 /* retries */, [&]() {
-    native_lcm->publish(channel_name, &message_);
+    native_lcm.publish(channel_name, &message_);
     total += dut_->HandleSubscriptions(50 /* millis */);
   });
   EXPECT_EQ(total, 1);
 }
 
 // Repeat SubscribeTest for SubscribeAllChannels.
 TEST_F(DrakeLcmTest, SubscribeAllTest) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.SubscribeAllTest";
 
   lcmt_drake_signal received{};
@@ -181,15 +183,15 @@ TEST_F(DrakeLcmTest, SubscribeAllTest) {
 
   int total = 0;
   LoopUntilDone(&received, 20 /* retries */, [&]() {
-    native_lcm->publish(channel_name, &message_);
+    native_lcm.publish(channel_name, &message_);
     total += dut_->HandleSubscriptions(50 /* millis */);
   });
   EXPECT_EQ(total, 1);
 }
 
 // Repeat SubscribeTest2 for SubscribeAllChannels.
 TEST_F(DrakeLcmTest, SubscribeAllTest2) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.SubscribeAllTest2";
 
   lcmt_drake_signal received{};
@@ -204,7 +206,7 @@ TEST_F(DrakeLcmTest, SubscribeAllTest2) {
 
   int total = 0;
   LoopUntilDone(&received, 20 /* retries */, [&]() {
-    native_lcm->publish(channel_name, &message_);
+    native_lcm.publish(channel_name, &message_);
     total += dut_->HandleSubscriptions(50 /* millis */);
   });
   EXPECT_EQ(total, 1);
@@ -369,7 +371,7 @@ TEST_F(DrakeLcmTest, Suffix) {
   DrakeLcmParams params;
   params.channel_suffix = "_SUFFIX";
   dut_ = std::make_unique<DrakeLcm>(params);
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
 
   // Subscribe using native LCM (with the fully-qualified channel name).
   lcmt_drake_signal received_native{};
@@ -379,7 +381,7 @@ TEST_F(DrakeLcmTest, Suffix) {
         DRAKE_DEMAND(new_value != nullptr);
         received_native = *new_value;
       };
-  native_lcm->subscribe("SuffixDrakeLcmTest_SUFFIX", std::move(handler));
+  native_lcm.subscribe("SuffixDrakeLcmTest_SUFFIX", std::move(handler));
 
   // Subscribe using Drake LCM (with the abbreviated channel name).
   lcmt_drake_signal received_drake{};
@@ -392,14 +394,14 @@ TEST_F(DrakeLcmTest, Suffix) {
   // Check that the native subscription gets it.
   LoopUntilDone(&received_native, 20 /* retries */, [&]() {
     Publish(dut_.get(), "SuffixDrakeLcmTest", message_);
-    native_lcm->handleTimeout(50 /* millis */);
+    native_lcm.handleTimeout(50 /* millis */);
   });
 
   // Publish using the abbreviated channel name.
   // Check that the drake subscription gets it.
   LoopUntilDone(&received_drake, 20 /* retries */, [&]() {
     Publish(dut_.get(), "SuffixDrakeLcmTest", message_);
-    native_lcm->handleTimeout(50 /* millis */);
+    native_lcm.handleTimeout(50 /* millis */);
   });
 }
 
@@ -439,7 +441,7 @@ TEST_F(DrakeLcmTest, SuffixInSubscribeAllChannels) {
 
 // Confirm that SubscribeMultichannel ignores mismatched channel names.
 TEST_F(DrakeLcmTest, SubscribeMultiTest) {
-  ::lcm::LCM* const native_lcm = get_native();
+  ::lcm::LCM native_lcm = get_native();
   const std::string channel_name = "DrakeLcmTest.SubscribeMultiTest";
 
   lcmt_drake_signal received{};
@@ -454,23 +456,13 @@ TEST_F(DrakeLcmTest, SubscribeMultiTest) {
 
   int total = 0;
   LoopUntilDone(&received, 20 /* retries */, [&]() {
-    native_lcm->publish("WRONG_" + channel_name, &message_);
-    native_lcm->publish(channel_name, &message_);
+    native_lcm.publish("WRONG_" + channel_name, &message_);
+    native_lcm.publish(channel_name, &message_);
     total += dut_->HandleSubscriptions(50 /* millis */);
   });
   EXPECT_EQ(total, 1);
 }
 
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-TEST_F(DrakeLcmTest, DeprecatedGetter) {
-  ::lcm::LCM* const deprecated = dut_->get_lcm_instance();
-  EXPECT_TRUE(deprecated != nullptr);
-  ::lcm::LCM* native = get_native();
-  EXPECT_TRUE(native == deprecated);
-}
-#pragma GCC diagnostic pop
-
 }  // namespace
 }  // namespace lcm
 }  // namespace drake
diff --git a/tools/install/libdrake/test/exported_symbols_test.py b/tools/install/libdrake/test/exported_symbols_test.py
@@ -86,8 +86,6 @@
     "slack_value",
     "sortOnOther",
     "wrapper",
-    # This fix is pending a deprecation removal (#20115) 2024-01-01.
-    "N3lcm",
 ]