diff --git a/audio/aidl/default/Android.bp b/audio/aidl/default/Android.bp
index 0a6fe60..4728a89 100644
--- a/audio/aidl/default/Android.bp
+++ b/audio/aidl/default/Android.bp
@@ -13,6 +13,7 @@
     shared_libs: [
         "libbase",
         "libbinder_ndk",
+        "android.media.audio.common.types-V1-ndk",
         "android.hardware.audio.core-V1-ndk",
     ],
     export_include_dirs: ["include"],
@@ -36,6 +37,7 @@
     shared_libs: [
         "libbase",
         "libbinder_ndk",
+        "android.media.audio.common.types-V1-ndk",
         "android.hardware.audio.core-V1-ndk",
     ],
     static_libs: [
diff --git a/audio/aidl/default/Configuration.cpp b/audio/aidl/default/Configuration.cpp
index 1104caa..19d0b3c 100644
--- a/audio/aidl/default/Configuration.cpp
+++ b/audio/aidl/default/Configuration.cpp
@@ -16,14 +16,15 @@
 
 #include <aidl/android/media/audio/common/AudioChannelLayout.h>
 #include <aidl/android/media/audio/common/AudioDeviceType.h>
+#include <aidl/android/media/audio/common/AudioFormatDescription.h>
 #include <aidl/android/media/audio/common/AudioFormatType.h>
 #include <aidl/android/media/audio/common/AudioIoFlags.h>
 #include <aidl/android/media/audio/common/AudioOutputFlags.h>
 
-#include "aidl/android/media/audio/common/AudioFormatDescription.h"
 #include "core-impl/Configuration.h"
 
 using aidl::android::media::audio::common::AudioChannelLayout;
+using aidl::android::media::audio::common::AudioDeviceDescription;
 using aidl::android::media::audio::common::AudioDeviceType;
 using aidl::android::media::audio::common::AudioFormatDescription;
 using aidl::android::media::audio::common::AudioFormatType;
@@ -54,9 +55,11 @@
     return profile;
 }
 
-static AudioPortExt createDeviceExt(AudioDeviceType devType, int32_t flags) {
+static AudioPortExt createDeviceExt(AudioDeviceType devType, int32_t flags,
+                                    std::string connection = "") {
     AudioPortDeviceExt deviceExt;
     deviceExt.device.type.type = devType;
+    deviceExt.device.type.connection = std::move(connection);
     deviceExt.flags = flags;
     return AudioPortExt::make<AudioPortExt::Tag::device>(deviceExt);
 }
@@ -102,8 +105,64 @@
     return route;
 }
 
+// Configuration:
+//
+// Device ports:
+//  * "Null", OUT_SPEAKER, default
+//    - no profiles specified
+//  * "Loopback Out", OUT_SUBMIX
+//    - profile PCM 24-bit; STEREO; 48000
+//  * "USB Out", OUT_DEVICE, CONNECTION_USB
+//    - no profiles specified
+//  * "Zero", IN_MICROPHONE, default
+//    - no profiles specified
+//  * "Loopback In", IN_SUBMIX
+//    - profile PCM 24-bit; STEREO; 48000
+//  * "USB In", IN_DEVICE, CONNECTION_USB
+//    - no profiles specified
+//
+// Mix ports:
+//  * "primary output", PRIMARY, 1 max open, 1 max active stream
+//    - profile PCM 16-bit; MONO, STEREO; 44100, 48000
+//    - profile PCM 24-bit; MONO, STEREO; 44100, 48000
+//  * "loopback output", stream count unlimited
+//    - profile PCM 24-bit; STEREO; 48000
+//  * "primary input", 2 max open, 2 max active streams
+//    - profile PCM 16-bit; MONO, STEREO, FRONT_BACK;
+//        8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, 48000
+//    - profile PCM 24-bit; MONO, STEREO, FRONT_BACK;
+//        8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, 48000
+//  * "loopback input", stream count unlimited
+//    - profile PCM 24-bit; STEREO; 48000
+//
+// Routes:
+//  "primary out" -> "Null"
+//  "primary out" -> "USB Out"
+//  "loopback out" -> "Loopback Out"
+//  "Zero", "USB In" -> "primary input"
+//  "Loopback In" -> "loopback input"
+//
+// Initial port configs:
+//  * "Null" device port: PCM 24-bit; STEREO; 48000
+//  * "Zero" device port: PCM 24-bit; MONO; 48000
+//
+// Profiles for device port connected state:
+//  * USB Out":
+//    - profile PCM 16-bit; MONO, STEREO; 44100, 48000
+//    - profile PCM 24-bit; MONO, STEREO; 44100, 48000
+//  * USB In":
+//    - profile PCM 16-bit; MONO, STEREO; 44100, 48000
+//    - profile PCM 24-bit; MONO, STEREO; 44100, 48000
+//
 Configuration& getNullPrimaryConfiguration() {
     static Configuration configuration = []() {
+        const std::vector<AudioProfile> standardPcmAudioProfiles = {
+                createProfile(PcmType::INT_16_BIT,
+                              {AudioChannelLayout::LAYOUT_MONO, AudioChannelLayout::LAYOUT_STEREO},
+                              {44100, 48000}),
+                createProfile(PcmType::INT_24_BIT,
+                              {AudioChannelLayout::LAYOUT_MONO, AudioChannelLayout::LAYOUT_STEREO},
+                              {44100, 48000})};
         Configuration c;
 
         AudioPort nullOutDevice =
@@ -111,27 +170,19 @@
                            createDeviceExt(AudioDeviceType::OUT_SPEAKER,
                                            1 << AudioPortDeviceExt::FLAG_INDEX_DEFAULT_DEVICE));
         c.ports.push_back(nullOutDevice);
-
-        AudioPort primaryOutMix = createPort(c.nextPortId++, "primary output",
-                                             1 << static_cast<int32_t>(AudioOutputFlags::PRIMARY),
-                                             false, createPortMixExt(1, 1));
-        primaryOutMix.profiles.push_back(
-                createProfile(PcmType::INT_16_BIT,
-                              {AudioChannelLayout::LAYOUT_MONO, AudioChannelLayout::LAYOUT_STEREO},
-                              {44100, 48000}));
-        primaryOutMix.profiles.push_back(
-                createProfile(PcmType::INT_24_BIT,
-                              {AudioChannelLayout::LAYOUT_MONO, AudioChannelLayout::LAYOUT_STEREO},
-                              {44100, 48000}));
-        c.ports.push_back(primaryOutMix);
-
-        c.routes.push_back(createRoute({primaryOutMix.id}, nullOutDevice.id));
-
         c.initialConfigs.push_back(
                 createPortConfig(nullOutDevice.id, nullOutDevice.id, PcmType::INT_24_BIT,
                                  AudioChannelLayout::LAYOUT_STEREO, 48000, 0, false,
                                  createDeviceExt(AudioDeviceType::OUT_SPEAKER, 0)));
 
+        AudioPort primaryOutMix = createPort(c.nextPortId++, "primary output",
+                                             1 << static_cast<int32_t>(AudioOutputFlags::PRIMARY),
+                                             false, createPortMixExt(1, 1));
+        primaryOutMix.profiles.insert(primaryOutMix.profiles.begin(),
+                                      standardPcmAudioProfiles.begin(),
+                                      standardPcmAudioProfiles.end());
+        c.ports.push_back(primaryOutMix);
+
         AudioPort loopOutDevice = createPort(c.nextPortId++, "Loopback Out", 0, false,
                                              createDeviceExt(AudioDeviceType::OUT_SUBMIX, 0));
         loopOutDevice.profiles.push_back(
@@ -144,13 +195,22 @@
                 createProfile(PcmType::INT_24_BIT, {AudioChannelLayout::LAYOUT_STEREO}, {48000}));
         c.ports.push_back(loopOutMix);
 
-        c.routes.push_back(createRoute({loopOutMix.id}, loopOutDevice.id));
+        AudioPort usbOutDevice =
+                createPort(c.nextPortId++, "USB Out", 0, false,
+                           createDeviceExt(AudioDeviceType::OUT_DEVICE, 0,
+                                           AudioDeviceDescription::CONNECTION_USB));
+        c.ports.push_back(usbOutDevice);
+        c.connectedProfiles[usbOutDevice.id] = standardPcmAudioProfiles;
 
         AudioPort zeroInDevice =
                 createPort(c.nextPortId++, "Zero", 0, true,
                            createDeviceExt(AudioDeviceType::IN_MICROPHONE,
                                            1 << AudioPortDeviceExt::FLAG_INDEX_DEFAULT_DEVICE));
         c.ports.push_back(zeroInDevice);
+        c.initialConfigs.push_back(
+                createPortConfig(zeroInDevice.id, zeroInDevice.id, PcmType::INT_24_BIT,
+                                 AudioChannelLayout::LAYOUT_MONO, 48000, 0, true,
+                                 createDeviceExt(AudioDeviceType::IN_MICROPHONE, 0)));
 
         AudioPort primaryInMix =
                 createPort(c.nextPortId++, "primary input", 0, true, createPortMixExt(2, 2));
@@ -166,13 +226,6 @@
                               {8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, 48000}));
         c.ports.push_back(primaryInMix);
 
-        c.routes.push_back(createRoute({zeroInDevice.id}, primaryInMix.id));
-
-        c.initialConfigs.push_back(
-                createPortConfig(zeroInDevice.id, zeroInDevice.id, PcmType::INT_24_BIT,
-                                 AudioChannelLayout::LAYOUT_MONO, 48000, 0, true,
-                                 createDeviceExt(AudioDeviceType::IN_MICROPHONE, 0)));
-
         AudioPort loopInDevice = createPort(c.nextPortId++, "Loopback In", 0, true,
                                             createDeviceExt(AudioDeviceType::IN_SUBMIX, 0));
         loopInDevice.profiles.push_back(
@@ -185,6 +238,16 @@
                 createProfile(PcmType::INT_24_BIT, {AudioChannelLayout::LAYOUT_STEREO}, {48000}));
         c.ports.push_back(loopInMix);
 
+        AudioPort usbInDevice = createPort(c.nextPortId++, "USB In", 0, true,
+                                           createDeviceExt(AudioDeviceType::IN_DEVICE, 0,
+                                                           AudioDeviceDescription::CONNECTION_USB));
+        c.ports.push_back(usbInDevice);
+        c.connectedProfiles[usbInDevice.id] = standardPcmAudioProfiles;
+
+        c.routes.push_back(createRoute({primaryOutMix.id}, nullOutDevice.id));
+        c.routes.push_back(createRoute({primaryOutMix.id}, usbOutDevice.id));
+        c.routes.push_back(createRoute({loopOutMix.id}, loopOutDevice.id));
+        c.routes.push_back(createRoute({zeroInDevice.id, usbInDevice.id}, primaryInMix.id));
         c.routes.push_back(createRoute({loopInDevice.id}, loopInMix.id));
 
         c.portConfigs.insert(c.portConfigs.end(), c.initialConfigs.begin(), c.initialConfigs.end());
diff --git a/audio/aidl/default/Module.cpp b/audio/aidl/default/Module.cpp
index e0a68a5..961ee84 100644
--- a/audio/aidl/default/Module.cpp
+++ b/audio/aidl/default/Module.cpp
@@ -18,7 +18,6 @@
 #include <set>
 
 #define LOG_TAG "AHAL_Module"
-#define LOG_NDEBUG 0
 #include <android-base/logging.h>
 
 #include <aidl/android/media/audio/common/AudioOutputFlags.h>
@@ -81,6 +80,7 @@
     }
     return false;
 }
+
 }  // namespace
 
 void Module::cleanUpPatch(int32_t patchId) {
@@ -135,6 +135,154 @@
     do_insert(patch.sinkPortConfigIds);
 }
 
+ndk::ScopedAStatus Module::setModuleDebug(
+        const ::aidl::android::hardware::audio::core::ModuleDebug& in_debug) {
+    LOG(DEBUG) << __func__ << ": old flags:" << mDebug.toString()
+               << ", new flags: " << in_debug.toString();
+    if (mDebug.simulateDeviceConnections != in_debug.simulateDeviceConnections &&
+        !mConnectedDevicePorts.empty()) {
+        LOG(ERROR) << __func__ << ": attempting to change device connections simulation "
+                   << "while having external devices connected";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    mDebug = in_debug;
+    return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus Module::connectExternalDevice(const AudioPort& in_templateIdAndAdditionalData,
+                                                 AudioPort* _aidl_return) {
+    const int32_t templateId = in_templateIdAndAdditionalData.id;
+    auto& ports = getConfig().ports;
+    AudioPort connectedPort;
+    {  // Scope the template port so that we don't accidentally modify it.
+        auto templateIt = findById<AudioPort>(ports, templateId);
+        if (templateIt == ports.end()) {
+            LOG(ERROR) << __func__ << ": port id " << templateId << " not found";
+            return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+        }
+        if (templateIt->ext.getTag() != AudioPortExt::Tag::device) {
+            LOG(ERROR) << __func__ << ": port id " << templateId << " is not a device port";
+            return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+        }
+        if (!templateIt->profiles.empty()) {
+            LOG(ERROR) << __func__ << ": port id " << templateId
+                       << " does not have dynamic profiles";
+            return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+        }
+        auto& templateDevicePort = templateIt->ext.get<AudioPortExt::Tag::device>();
+        if (templateDevicePort.device.type.connection.empty()) {
+            LOG(ERROR) << __func__ << ": port id " << templateId << " is permanently attached";
+            return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+        }
+        // Postpone id allocation until we ensure that there are no client errors.
+        connectedPort = *templateIt;
+        connectedPort.extraAudioDescriptors = in_templateIdAndAdditionalData.extraAudioDescriptors;
+        const auto& inputDevicePort =
+                in_templateIdAndAdditionalData.ext.get<AudioPortExt::Tag::device>();
+        auto& connectedDevicePort = connectedPort.ext.get<AudioPortExt::Tag::device>();
+        connectedDevicePort.device.address = inputDevicePort.device.address;
+        LOG(DEBUG) << __func__ << ": device port " << connectedPort.id << " device set to "
+                   << connectedDevicePort.device.toString();
+        // Check if there is already a connected port with for the same external device.
+        for (auto connectedPortId : mConnectedDevicePorts) {
+            auto connectedPortIt = findById<AudioPort>(ports, connectedPortId);
+            if (connectedPortIt->ext.get<AudioPortExt::Tag::device>().device ==
+                connectedDevicePort.device) {
+                LOG(ERROR) << __func__ << ": device " << connectedDevicePort.device.toString()
+                           << " is already connected at the device port id " << connectedPortId;
+                return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+            }
+        }
+    }
+
+    if (!mDebug.simulateDeviceConnections) {
+        // In a real HAL here we would attempt querying the profiles from the device.
+        LOG(ERROR) << __func__ << ": failed to query supported device profiles";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+
+    connectedPort.id = ++getConfig().nextPortId;
+    mConnectedDevicePorts.insert(connectedPort.id);
+    LOG(DEBUG) << __func__ << ": template port " << templateId << " external device connected, "
+               << "connected port ID " << connectedPort.id;
+    auto& connectedProfiles = getConfig().connectedProfiles;
+    if (auto connectedProfilesIt = connectedProfiles.find(templateId);
+        connectedProfilesIt != connectedProfiles.end()) {
+        connectedPort.profiles = connectedProfilesIt->second;
+    }
+    ports.push_back(connectedPort);
+    *_aidl_return = std::move(connectedPort);
+
+    std::vector<AudioRoute> newRoutes;
+    auto& routes = getConfig().routes;
+    for (auto& r : routes) {
+        if (r.sinkPortId == templateId) {
+            AudioRoute newRoute;
+            newRoute.sourcePortIds = r.sourcePortIds;
+            newRoute.sinkPortId = connectedPort.id;
+            newRoute.isExclusive = r.isExclusive;
+            newRoutes.push_back(std::move(newRoute));
+        } else {
+            auto& srcs = r.sourcePortIds;
+            if (std::find(srcs.begin(), srcs.end(), templateId) != srcs.end()) {
+                srcs.push_back(connectedPort.id);
+            }
+        }
+    }
+    routes.insert(routes.end(), newRoutes.begin(), newRoutes.end());
+
+    return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus Module::disconnectExternalDevice(int32_t in_portId) {
+    auto& ports = getConfig().ports;
+    auto portIt = findById<AudioPort>(ports, in_portId);
+    if (portIt == ports.end()) {
+        LOG(ERROR) << __func__ << ": port id " << in_portId << " not found";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+    }
+    if (portIt->ext.getTag() != AudioPortExt::Tag::device) {
+        LOG(ERROR) << __func__ << ": port id " << in_portId << " is not a device port";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+    }
+    if (mConnectedDevicePorts.count(in_portId) == 0) {
+        LOG(ERROR) << __func__ << ": port id " << in_portId << " is not a connected device port";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+    }
+    auto& configs = getConfig().portConfigs;
+    auto& initials = getConfig().initialConfigs;
+    auto configIt = std::find_if(configs.begin(), configs.end(), [&](const auto& config) {
+        if (config.portId == in_portId) {
+            // Check if the configuration was provided by the client.
+            const auto& initialIt = findById<AudioPortConfig>(initials, config.id);
+            return initialIt == initials.end() || config != *initialIt;
+        }
+        return false;
+    });
+    if (configIt != configs.end()) {
+        LOG(ERROR) << __func__ << ": port id " << in_portId << " has a non-default config with id "
+                   << configIt->id;
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    ports.erase(portIt);
+    mConnectedDevicePorts.erase(in_portId);
+    LOG(DEBUG) << __func__ << ": connected device port " << in_portId << " released";
+
+    auto& routes = getConfig().routes;
+    for (auto routesIt = routes.begin(); routesIt != routes.end();) {
+        if (routesIt->sinkPortId == in_portId) {
+            routesIt = routes.erase(routesIt);
+        } else {
+            // Note: the list of sourcePortIds can't become empty because there must
+            // be the id of the template port in the route.
+            erase_if(routesIt->sourcePortIds, [in_portId](auto src) { return src == in_portId; });
+            ++routesIt;
+        }
+    }
+
+    return ndk::ScopedAStatus::ok();
+}
+
 ndk::ScopedAStatus Module::getAudioPatches(std::vector<AudioPatch>* _aidl_return) {
     *_aidl_return = getConfig().patches;
     LOG(DEBUG) << __func__ << ": returning " << _aidl_return->size() << " patches";
@@ -171,6 +319,23 @@
     return ndk::ScopedAStatus::ok();
 }
 
+ndk::ScopedAStatus Module::getAudioRoutesForAudioPort(int32_t in_portId,
+                                                      std::vector<AudioRoute>* _aidl_return) {
+    auto& ports = getConfig().ports;
+    if (auto portIt = findById<AudioPort>(ports, in_portId); portIt == ports.end()) {
+        LOG(ERROR) << __func__ << ": port id " << in_portId << " not found";
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+    }
+    auto& routes = getConfig().routes;
+    std::copy_if(routes.begin(), routes.end(), std::back_inserter(*_aidl_return),
+                 [&](const auto& r) {
+                     const auto& srcs = r.sourcePortIds;
+                     return r.sinkPortId == in_portId ||
+                            std::find(srcs.begin(), srcs.end(), in_portId) != srcs.end();
+                 });
+    return ndk::ScopedAStatus::ok();
+}
+
 ndk::ScopedAStatus Module::openInputStream(int32_t in_portConfigId,
                                            const SinkMetadata& in_sinkMetadata,
                                            std::shared_ptr<IStreamIn>* _aidl_return) {
diff --git a/audio/aidl/default/include/core-impl/Configuration.h b/audio/aidl/default/include/core-impl/Configuration.h
index 17e342d..d5cd30b 100644
--- a/audio/aidl/default/include/core-impl/Configuration.h
+++ b/audio/aidl/default/include/core-impl/Configuration.h
@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <map>
 #include <vector>
 
 #include <aidl/android/hardware/audio/core/AudioPatch.h>
@@ -29,6 +30,9 @@
     std::vector<::aidl::android::media::audio::common::AudioPort> ports;
     std::vector<::aidl::android::media::audio::common::AudioPortConfig> portConfigs;
     std::vector<::aidl::android::media::audio::common::AudioPortConfig> initialConfigs;
+    // Port id -> List of profiles to use when the device port state is set to 'connected'.
+    std::map<int32_t, std::vector<::aidl::android::media::audio::common::AudioProfile>>
+            connectedProfiles;
     std::vector<AudioRoute> routes;
     std::vector<AudioPatch> patches;
     int32_t nextPortId = 1;
diff --git a/audio/aidl/default/include/core-impl/Module.h b/audio/aidl/default/include/core-impl/Module.h
index 359626c..81a02ba 100644
--- a/audio/aidl/default/include/core-impl/Module.h
+++ b/audio/aidl/default/include/core-impl/Module.h
@@ -18,6 +18,7 @@
 
 #include <map>
 #include <memory>
+#include <set>
 
 #include <aidl/android/hardware/audio/core/BnModule.h>
 
@@ -27,6 +28,12 @@
 namespace aidl::android::hardware::audio::core {
 
 class Module : public BnModule {
+    ndk::ScopedAStatus setModuleDebug(
+            const ::aidl::android::hardware::audio::core::ModuleDebug& in_debug) override;
+    ndk::ScopedAStatus connectExternalDevice(
+            const ::aidl::android::media::audio::common::AudioPort& in_templateIdAndAdditionalData,
+            ::aidl::android::media::audio::common::AudioPort* _aidl_return) override;
+    ndk::ScopedAStatus disconnectExternalDevice(int32_t in_portId) override;
     ndk::ScopedAStatus getAudioPatches(std::vector<AudioPatch>* _aidl_return) override;
     ndk::ScopedAStatus getAudioPort(
             int32_t in_portId,
@@ -37,6 +44,9 @@
     ndk::ScopedAStatus getAudioPorts(
             std::vector<::aidl::android::media::audio::common::AudioPort>* _aidl_return) override;
     ndk::ScopedAStatus getAudioRoutes(std::vector<AudioRoute>* _aidl_return) override;
+    ndk::ScopedAStatus getAudioRoutesForAudioPort(
+            int32_t in_portId,
+            std::vector<::aidl::android::hardware::audio::core::AudioRoute>* _aidl_return) override;
     ndk::ScopedAStatus openInputStream(
             int32_t in_portConfigId,
             const ::aidl::android::hardware::audio::common::SinkMetadata& in_sinkMetadata,
@@ -63,6 +73,9 @@
     void registerPatch(const AudioPatch& patch);
 
     std::unique_ptr<internal::Configuration> mConfig;
+    ModuleDebug mDebug;
+    // ids of ports created at runtime via 'connectExternalDevice'.
+    std::set<int32_t> mConnectedDevicePorts;
     Streams mStreams;
     // Maps port ids and port config ids to patch ids.
     // Multimap because both ports and configs can be used by multiple patches.
diff --git a/audio/aidl/default/include/core-impl/utils.h b/audio/aidl/default/include/core-impl/utils.h
index 7101012..9d06f08 100644
--- a/audio/aidl/default/include/core-impl/utils.h
+++ b/audio/aidl/default/include/core-impl/utils.h
@@ -38,11 +38,11 @@
     return oldSize - c.size();
 }
 
-// Erase all the elements in the map that satisfy the provided predicate.
+// Erase all the elements in the container that satisfy the provided predicate.
 template <typename C, typename P>
 auto erase_if(C& c, P pred) {
     auto oldSize = c.size();
-    for (auto it = c.begin(), last = c.end(); it != last;) {
+    for (auto it = c.begin(); it != c.end();) {
         if (pred(*it)) {
             it = c.erase(it);
         } else {