diff --git a/cmds/atrace/atrace.cpp b/cmds/atrace/atrace.cpp
index 9cdc9e9..a48dab9 100644
--- a/cmds/atrace/atrace.cpp
+++ b/cmds/atrace/atrace.cpp
@@ -481,8 +481,8 @@
         newClock = "global";
     }
 
-    size_t begin = clockStr.find("[") + 1;
-    size_t end = clockStr.find("]");
+    size_t begin = clockStr.find('[') + 1;
+    size_t end = clockStr.find(']');
     if (newClock.compare(0, std::string::npos, clockStr, begin, end-begin) == 0) {
         return true;
     }
@@ -543,7 +543,7 @@
     auto listRet = sm->list([&](const auto &interfaces) {
         for (size_t i = 0; i < interfaces.size(); i++) {
             string fqInstanceName = interfaces[i];
-            string::size_type n = fqInstanceName.find("/");
+            string::size_type n = fqInstanceName.find('/');
             if (n == std::string::npos || interfaces[i].size() == n+1)
                 continue;
             hidl_string fqInterfaceName = fqInstanceName.substr(0, n);
diff --git a/cmds/dumpstate/dumpstate.cpp b/cmds/dumpstate/dumpstate.cpp
index 657323d..9e77e8f 100644
--- a/cmds/dumpstate/dumpstate.cpp
+++ b/cmds/dumpstate/dumpstate.cpp
@@ -691,7 +691,7 @@
     std::string valid_name = entry_name;
 
     // Rename extension if necessary.
-    size_t idx = entry_name.rfind(".");
+    size_t idx = entry_name.rfind('.');
     if (idx != std::string::npos) {
         std::string extension = entry_name.substr(idx);
         std::transform(extension.begin(), extension.end(), extension.begin(), ::tolower);
@@ -1432,7 +1432,7 @@
     return true;
 }
 
-static std::string SHA256_file_hash(std::string filepath) {
+static std::string SHA256_file_hash(const std::string& filepath) {
     android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(filepath.c_str(), O_RDONLY | O_NONBLOCK
             | O_CLOEXEC | O_NOFOLLOW)));
     if (fd == -1) {
diff --git a/cmds/dumpsys/dumpsys.cpp b/cmds/dumpsys/dumpsys.cpp
index f0e7200..73c7f18 100644
--- a/cmds/dumpsys/dumpsys.cpp
+++ b/cmds/dumpsys/dumpsys.cpp
@@ -176,7 +176,7 @@
     }
 
     for (size_t i = 0; i < N; i++) {
-        String16 service_name = std::move(services[i]);
+        const String16& service_name = std::move(services[i]);
         if (IsSkipped(skippedServices, service_name)) continue;
 
         sp<IBinder> service = sm_->checkService(service_name);
diff --git a/cmds/dumpsys/tests/dumpsys_test.cpp b/cmds/dumpsys/tests/dumpsys_test.cpp
index 66beb6d..5ca2b57 100644
--- a/cmds/dumpsys/tests/dumpsys_test.cpp
+++ b/cmds/dumpsys/tests/dumpsys_test.cpp
@@ -95,7 +95,7 @@
     }
     int i = 0;
     std::ostringstream actual_stream, expected_stream;
-    for (String16 actual : arg) {
+    for (const String16& actual : arg) {
         std::string actual_str = String8(actual).c_str();
         std::string expected_str = expected[i];
         actual_stream << "'" << actual_str << "' ";
diff --git a/cmds/installd/CacheTracker.cpp b/cmds/installd/CacheTracker.cpp
index 3eb39b9..ea0cd9e 100644
--- a/cmds/installd/CacheTracker.cpp
+++ b/cmds/installd/CacheTracker.cpp
@@ -60,7 +60,7 @@
 
     ATRACE_BEGIN("loadStats tree");
     cacheUsed = 0;
-    for (auto path : mDataPaths) {
+    for (const auto& path : mDataPaths) {
         auto cachePath = read_path_inode(path, "cache", kXattrInodeCache);
         auto codeCachePath = read_path_inode(path, "code_cache", kXattrInodeCodeCache);
         calculate_tree_size(cachePath, &cacheUsed);
@@ -170,7 +170,7 @@
     items.clear();
 
     ATRACE_BEGIN("loadItems");
-    for (auto path : mDataPaths) {
+    for (const auto& path : mDataPaths) {
         loadItemsFrom(read_path_inode(path, "cache", kXattrInodeCache));
         loadItemsFrom(read_path_inode(path, "code_cache", kXattrInodeCodeCache));
     }
diff --git a/cmds/installd/InstalldNativeService.cpp b/cmds/installd/InstalldNativeService.cpp
index a711813..79c77dc 100644
--- a/cmds/installd/InstalldNativeService.cpp
+++ b/cmds/installd/InstalldNativeService.cpp
@@ -1344,7 +1344,7 @@
         const std::vector<std::string>& codePaths, std::vector<int64_t>* _aidl_return) {
     ENFORCE_UID(AID_SYSTEM);
     CHECK_ARGUMENT_UUID(uuid);
-    for (auto packageName : packageNames) {
+    for (const auto& packageName : packageNames) {
         CHECK_ARGUMENT_PACKAGE_NAME(packageName);
     }
     // NOTE: Locking is relaxed on this method, since it's limited to
@@ -1383,7 +1383,7 @@
     }
 
     ATRACE_BEGIN("obb");
-    for (auto packageName : packageNames) {
+    for (const auto& packageName : packageNames) {
         auto obbCodePath = create_data_media_obb_path(uuid_, packageName.c_str());
         calculate_tree_size(obbCodePath, &extStats.codeSize);
     }
@@ -1391,7 +1391,7 @@
 
     if (flags & FLAG_USE_QUOTA && appId >= AID_APP_START) {
         ATRACE_BEGIN("code");
-        for (auto codePath : codePaths) {
+        for (const auto& codePath : codePaths) {
             calculate_tree_size(codePath, &stats.codeSize, -1,
                     multiuser_get_shared_gid(0, appId));
         }
@@ -1402,7 +1402,7 @@
         ATRACE_END();
     } else {
         ATRACE_BEGIN("code");
-        for (auto codePath : codePaths) {
+        for (const auto& codePath : codePaths) {
             calculate_tree_size(codePath, &stats.codeSize);
         }
         ATRACE_END();
diff --git a/cmds/surfacereplayer/replayer/Replayer.cpp b/cmds/surfacereplayer/replayer/Replayer.cpp
index 35b63ec..2b5389b 100644
--- a/cmds/surfacereplayer/replayer/Replayer.cpp
+++ b/cmds/surfacereplayer/replayer/Replayer.cpp
@@ -505,7 +505,7 @@
     ALOGV("Setting Transparent Region Hint");
     Region re = Region();
 
-    for (auto r : trhc.region()) {
+    for (const auto& r : trhc.region()) {
         Rect rect = Rect(r.left(), r.top(), r.right(), r.bottom());
         re.merge(rect);
     }
diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index 3424012..bcfa7bc 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -764,7 +764,7 @@
     input.deflate(&requestedPresentTimestamp, &isAutoTimestamp, &dataSpace,
             &crop, &scalingMode, &transform, &acquireFence, &stickyTransform,
             &getFrameTimestamps);
-    Region surfaceDamage = input.getSurfaceDamage();
+    const Region& surfaceDamage = input.getSurfaceDamage();
 
     if (acquireFence == NULL) {
         BQ_LOGE("queueBuffer: fence is NULL");
diff --git a/opengl/tests/hwc/hwcRects.cpp b/opengl/tests/hwc/hwcRects.cpp
index 69e56ff..5956366 100644
--- a/opengl/tests/hwc/hwcRects.cpp
+++ b/opengl/tests/hwc/hwcRects.cpp
@@ -170,7 +170,7 @@
 static EGLint width, height;
 
 // Function prototypes
-static Rectangle parseRect(string rectStr);
+static Rectangle parseRect(const string& rectStr);
 void init(void);
 void printSyntax(const char *cmd);
 
@@ -358,7 +358,7 @@
 
 // Parse string description of rectangle and add it to list of rectangles
 // to be rendered.
-static Rectangle parseRect(string rectStr)
+static Rectangle parseRect(const string& rectStr)
 {
     int rv;
     string str;