diff --git a/base/big_endian.cc b/base/big_endian.cc
index 9e9e672e4..a706c4a4e 100644
--- a/base/big_endian.cc
+++ b/base/big_endian.cc
@@ -4,6 +4,8 @@
 
 #include "base/big_endian.h"
 
+#include <string.h>
+
 #include "base/numerics/checked_math.h"
 #include "base/strings/string_piece.h"
 
diff --git a/base/check_op.cc b/base/check_op.cc
index 7e0806464..fcdb8df16 100644
--- a/base/check_op.cc
+++ b/base/check_op.cc
@@ -12,6 +12,7 @@
 #endif
 
 #include <cstdio>
+#include <cstring>
 #include <sstream>
 
 namespace logging {
diff --git a/base/debug/elf_reader.cc b/base/debug/elf_reader.cc
index aea4f3b03..1cf7bf50d 100644
--- a/base/debug/elf_reader.cc
+++ b/base/debug/elf_reader.cc
@@ -4,6 +4,7 @@
 
 #include "base/debug/elf_reader.h"
 
+#include <string.h>
 #include <arpa/inet.h>
 #include <elf.h>
 
diff --git a/base/files/dir_reader_linux.h b/base/files/dir_reader_linux.h
index f12deeb2f..194cd92b0 100644
--- a/base/files/dir_reader_linux.h
+++ b/base/files/dir_reader_linux.h
@@ -7,6 +7,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <string.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <sys/syscall.h>
diff --git a/base/logging.h b/base/logging.h
index 7644ec188..848718612 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -6,6 +6,7 @@
 #define BASE_LOGGING_H_
 
 #include <stddef.h>
+#include <string.h>
 
 #include <cassert>
 #include <cstdint>
diff --git a/base/metrics/metrics_hashes.cc b/base/metrics/metrics_hashes.cc
index ef7072a4a..9cd2d5a93 100644
--- a/base/metrics/metrics_hashes.cc
+++ b/base/metrics/metrics_hashes.cc
@@ -4,6 +4,8 @@
 
 #include "base/metrics/metrics_hashes.h"
 
+#include <string.h>
+
 #include "base/hash/md5.h"
 #include "base/logging.h"
 #include "base/sys_byteorder.h"
diff --git a/base/process/environment_internal.cc b/base/process/environment_internal.cc
index 357140fa6..44f5c6603 100644
--- a/base/process/environment_internal.cc
+++ b/base/process/environment_internal.cc
@@ -5,6 +5,7 @@
 #include "base/process/environment_internal.h"
 
 #include <stddef.h>
+#include <string.h>
 
 #include <vector>
 
diff --git a/base/strings/string16.cc b/base/strings/string16.cc
index 84962e671..b7df7e161 100644
--- a/base/strings/string16.cc
+++ b/base/strings/string16.cc
@@ -4,6 +4,8 @@
 
 #include "base/strings/string16.h"
 
+#include <string.h>
+
 #if defined(WCHAR_T_IS_UTF16) && !defined(_AIX)
 
 #error This file should not be used on 2-byte wchar_t systems
diff --git a/base/strings/string_piece.cc b/base/strings/string_piece.cc
index c789bc2a0..bfaf99db5 100644
--- a/base/strings/string_piece.cc
+++ b/base/strings/string_piece.cc
@@ -5,6 +5,7 @@
 
 #include "base/strings/string_piece.h"
 
+#include <string.h>
 #include <limits.h>
 
 #include <algorithm>
diff --git a/base/strings/sys_string_conversions_posix.cc b/base/strings/sys_string_conversions_posix.cc
index ad794cae2..dad27eaa5 100644
--- a/base/strings/sys_string_conversions_posix.cc
+++ b/base/strings/sys_string_conversions_posix.cc
@@ -4,6 +4,7 @@
 
 #include "base/strings/sys_string_conversions.h"
 
+#include <string.h>
 #include <stddef.h>
 #include <wchar.h>
 
diff --git a/base/synchronization/lock_impl.h b/base/synchronization/lock_impl.h
index 830b878e8..cdb66fdca 100644
--- a/base/synchronization/lock_impl.h
+++ b/base/synchronization/lock_impl.h
@@ -16,6 +16,7 @@
 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
 #include <errno.h>
 #include <pthread.h>
+#include <string.h>
 #endif
 
 namespace base {
diff --git a/base/trace_event/blame_context.cc b/base/trace_event/blame_context.cc
index e7599efa8..4b82c5526 100644
--- a/base/trace_event/blame_context.cc
+++ b/base/trace_event/blame_context.cc
@@ -25,7 +25,7 @@ BlameContext::BlameContext(const char* category,
       parent_scope_(parent_context ? parent_context->scope() : nullptr),
       parent_id_(parent_context ? parent_context->id() : 0),
       category_group_enabled_(nullptr) {
-  DCHECK(!parent_context || !std::strcmp(name_, parent_context->name()))
+  DCHECK(!parent_context || !strcmp(name_, parent_context->name()))
       << "Parent blame context must have the same name";
 }
 
diff --git a/components/network_hints/renderer/dns_prefetch_queue.cc b/components/network_hints/renderer/dns_prefetch_queue.cc
index af34d8df0..7905ad49d 100644
--- a/components/network_hints/renderer/dns_prefetch_queue.cc
+++ b/components/network_hints/renderer/dns_prefetch_queue.cc
@@ -6,8 +6,11 @@
 
 #include "components/network_hints/renderer/dns_prefetch_queue.h"
 
+#include <cstring>
+
 #include "base/logging.h"
 
+
 namespace network_hints {
 
 DnsQueue::DnsQueue(BufferSize size)
diff --git a/components/omnibox/browser/on_device_head_model.cc b/components/omnibox/browser/on_device_head_model.cc
index 0fa2ff25e..ad5e9386f 100644
--- a/components/omnibox/browser/on_device_head_model.cc
+++ b/components/omnibox/browser/on_device_head_model.cc
@@ -4,6 +4,7 @@
 
 #include "components/omnibox/browser/on_device_head_model.h"
 
+#include <cstring>
 #include <algorithm>
 
 #include "base/logging.h"
diff --git a/google_apis/gcm/base/socket_stream.cc b/google_apis/gcm/base/socket_stream.cc
index d9759e767..bc33dca40 100644
--- a/google_apis/gcm/base/socket_stream.cc
+++ b/google_apis/gcm/base/socket_stream.cc
@@ -177,7 +177,7 @@ void SocketInputStream::RebuildBuffer() {
     DVLOG(1) << "Have " << unread_data_size
              << " unread bytes remaining, shifting.";
     // Move any remaining unread data to the start of the buffer;
-    std::memmove(io_buffer_->data(), unread_data_ptr, unread_data_size);
+    memmove(io_buffer_->data(), unread_data_ptr, unread_data_size);
   } else {
     DVLOG(1) << "Have " << unread_data_size << " unread bytes remaining.";
   }
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index f4c3014d1..7491797e7 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -9,6 +9,7 @@
 
 #include <stdint.h>
 
+#include <cstring>
 #include <string>
 #include <vector>
 
diff --git a/gpu/vulkan/vulkan_device_queue.cc b/gpu/vulkan/vulkan_device_queue.cc
index 4d95330b5..a6a130593 100644
--- a/gpu/vulkan/vulkan_device_queue.cc
+++ b/gpu/vulkan/vulkan_device_queue.cc
@@ -98,7 +98,7 @@ bool VulkanDeviceQueue::Initialize(
         std::find_if(physical_device_info.extensions.begin(),
                      physical_device_info.extensions.end(),
                      [extension](const VkExtensionProperties& p) {
-                       return std::strcmp(extension, p.extensionName) == 0;
+                       return strcmp(extension, p.extensionName) == 0;
                      });
     if (it == physical_device_info.extensions.end()) {
       // On Fuchsia, some device extensions are provided by layers.
@@ -118,7 +118,7 @@ bool VulkanDeviceQueue::Initialize(
         std::find_if(physical_device_info.extensions.begin(),
                      physical_device_info.extensions.end(),
                      [extension](const VkExtensionProperties& p) {
-                       return std::strcmp(extension, p.extensionName) == 0;
+                       return strcmp(extension, p.extensionName) == 0;
                      });
     if (it == physical_device_info.extensions.end()) {
       DLOG(ERROR) << "Optional Vulkan extension " << extension
@@ -255,4 +255,4 @@ std::unique_ptr<VulkanCommandPool> VulkanDeviceQueue::CreateCommandPool() {
   return command_pool;
 }
 
-}  // namespace gpu
\ No newline at end of file
+}  // namespace gpu
diff --git a/jingle/glue/fake_ssl_client_socket.cc b/jingle/glue/fake_ssl_client_socket.cc
index 54691d935..c61c6c8a1 100644
--- a/jingle/glue/fake_ssl_client_socket.cc
+++ b/jingle/glue/fake_ssl_client_socket.cc
@@ -7,6 +7,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <cstdlib>
+#include <cstring>
 #include <utility>
 
 #include "base/bind.h"
diff --git a/net/base/datagram_buffer.cc b/net/base/datagram_buffer.cc
index 922d8486e..b7f737405 100644
--- a/net/base/datagram_buffer.cc
+++ b/net/base/datagram_buffer.cc
@@ -42,7 +42,7 @@ DatagramBuffer::~DatagramBuffer() {}
 
 void DatagramBuffer::Set(const char* buffer, size_t buf_len) {
   length_ = buf_len;
-  std::memcpy(data_.get(), buffer, buf_len);
+  memcpy(data_.get(), buffer, buf_len);
 }
 
 char* DatagramBuffer::data() const {
diff --git a/net/reporting/reporting_header_parser.cc b/net/reporting/reporting_header_parser.cc
index 3701d15bf..fc144ed63 100644
--- a/net/reporting/reporting_header_parser.cc
+++ b/net/reporting/reporting_header_parser.cc
@@ -81,7 +81,7 @@ HeaderEndpointOutcome ProcessEndpoint(
 
   GURL endpoint_url;
   // Support path-absolute-URL string
-  if (std::strspn(endpoint_url_string.c_str(), "/") == 1) {
+  if (strspn(endpoint_url_string.c_str(), "/") == 1) {
     endpoint_url = group_key.origin.GetURL().Resolve(endpoint_url_string);
   } else {
     endpoint_url = GURL(endpoint_url_string);
diff --git a/third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc b/third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc
index fbfdfedff..3b9fd967e 100644
--- a/third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc
+++ b/third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc
@@ -891,7 +891,7 @@ void NGInlineNode::SegmentText(NGInlineNodeData* data) {
 
 // Segment NGInlineItem by script, Emoji, and orientation using RunSegmenter.
 void NGInlineNode::SegmentScriptRuns(NGInlineNodeData* data) {
-  DCHECK_EQ(data->segments, nullptr);
+  DCHECK_EQ(data->segments.get(), nullptr);
 
   String& text_content = data->text_content;
   if (text_content.IsEmpty()) {