diff --git a/configure.ac b/configure.ac
index 74b6073381eda..106db424a9c5c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -550,13 +550,17 @@ AX_CHECK_COMPILE_FLAG([-march=armv8-a+crc+crypto],[[ARM_CRC_CXXFLAGS="-march=arm
 
 TEMP_CXXFLAGS="$CXXFLAGS"
 CXXFLAGS="$CXXFLAGS $ARM_CRC_CXXFLAGS"
-AC_MSG_CHECKING(for ARM CRC32 intrinsics)
+AC_MSG_CHECKING(for AArch64 CRC32 intrinsics)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
     #include <arm_acle.h>
     #include <arm_neon.h>
   ]],[[
+#ifdef __aarch64__
     __crc32cb(0, 0); __crc32ch(0, 0); __crc32cw(0, 0); __crc32cd(0, 0);
     vmull_p64(0, 0);
+#else
+#error "crc32c library does not support hardware acceleration on 32-bit ARM"
+#endif
   ]])],
  [ AC_MSG_RESULT(yes); enable_arm_crc=yes; ],
  [ AC_MSG_RESULT(no)]
diff --git a/contrib/macdeploy/README.md b/contrib/macdeploy/README.md
index d3f05de6077ad..73cbd71e8c5d4 100644
--- a/contrib/macdeploy/README.md
+++ b/contrib/macdeploy/README.md
@@ -20,7 +20,10 @@ Our current macOS SDK
 (`Xcode-12.1-12A7403-extracted-SDK-with-libcxx-headers.tar.gz`) can be
 extracted from
 [Xcode_12.1.xip](https://download.developer.apple.com/Developer_Tools/Xcode_12.1/Xcode_12.1.xip).
-An Apple ID is needed to download this.
+Alternatively, after logging in to your account go to 'Downloads', then 'More'
+and look for [`Xcode_12.1`](https://download.developer.apple.com/Developer_Tools/Xcode_12.1/Xcode_12.1.xip).
+An Apple ID and cookies enabled for the hostname are needed to download this.
+The `sha256sum` of the archive should be `612443b1894b39368a596ea1607f30cbb0481ad44d5e29c75edb71a6d2cf050f`.
 
 After Xcode version 7.x, Apple started shipping the `Xcode.app` in a `.xip`
 archive. This makes the SDK less-trivial to extract on non-macOS machines. One
@@ -80,7 +83,7 @@ and its `libLTO.so` rather than those from `llvmgcc`, as it was originally done
 
 To complicate things further, all builds must target an Apple SDK. These SDKs are free to
 download, but not redistributable. To obtain it, register for an Apple Developer Account,
-then download [Xcode_11.3.1](https://download.developer.apple.com/Developer_Tools/Xcode_11.3.1/Xcode_11.3.1.xip).
+then download [Xcode_12.1](https://download.developer.apple.com/Developer_Tools/Xcode_12.1/Xcode_12.1.xip).
 
 This file is many gigabytes in size, but most (but not all) of what we need is
 contained only in a single directory:
diff --git a/doc/Doxyfile.in b/doc/Doxyfile.in
index ba3307198de22..e1f94347f0068 100644
--- a/doc/Doxyfile.in
+++ b/doc/Doxyfile.in
@@ -878,9 +878,7 @@ RECURSIVE              = YES
 
 EXCLUDE                = src/crc32c \
                          src/leveldb \
-                         src/json \
-                         src/test \
-                         src/qt/test
+                         src/json
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded
diff --git a/src/crc32c/.travis.yml b/src/crc32c/.travis.yml
index d990a89f0750d..183a5fba45fff 100644
--- a/src/crc32c/.travis.yml
+++ b/src/crc32c/.travis.yml
@@ -4,7 +4,7 @@
 
 language: cpp
 dist: bionic
-osx_image: xcode10.3
+osx_image: xcode12.5
 
 compiler:
 - gcc
@@ -24,20 +24,20 @@ env:
 addons:
   apt:
     sources:
-    - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
+    - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main'
       key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
     - sourceline: 'ppa:ubuntu-toolchain-r/test'
     packages:
-    - clang-9
+    - clang-12
     - cmake
-    - gcc-9
-    - g++-9
+    - gcc-11
+    - g++-11
     - ninja-build
   homebrew:
     packages:
     - cmake
-    - gcc@9
-    - llvm@9
+    - gcc@11
+    - llvm@12
     - ninja
     update: true
 
@@ -48,14 +48,14 @@ install:
     export PATH="$(brew --prefix llvm)/bin:$PATH";
   fi
 # /usr/bin/gcc points to an older compiler on both Linux and macOS.
-- if [ "$CXX" = "g++" ]; then export CXX="g++-9" CC="gcc-9"; fi
+- if [ "$CXX" = "g++" ]; then export CXX="g++-11" CC="gcc-11"; fi
 # /usr/bin/clang points to an older compiler on both Linux and macOS.
 #
 # Homebrew's llvm package doesn't ship a versioned clang++ binary, so the values
 # below don't work on macOS. Fortunately, the path change above makes the
 # default values (clang and clang++) resolve to the correct compiler on macOS.
 - if [ "$TRAVIS_OS_NAME" = "linux" ]; then
-    if [ "$CXX" = "clang++" ]; then export CXX="clang++-9" CC="clang-9"; fi;
+    if [ "$CXX" = "clang++" ]; then export CXX="clang++-12" CC="clang-12"; fi;
   fi
 - echo ${CC}
 - echo ${CXX}
diff --git a/src/crc32c/.ycm_extra_conf.py b/src/crc32c/.ycm_extra_conf.py
index 536aadcec8cf6..62daa8a4acf6d 100644
--- a/src/crc32c/.ycm_extra_conf.py
+++ b/src/crc32c/.ycm_extra_conf.py
@@ -4,10 +4,10 @@
 """YouCompleteMe configuration that interprets a .clang_complete file.
 
 This module implementes the YouCompleteMe configuration API documented at:
-https://github.com/Valloric/ycmd#ycm_extra_confpy-specification
+https://github.com/ycm-core/ycmd#ycm_extra_confpy-specification
 
 The implementation loads and processes a .clang_complete file, documented at:
-https://github.com/Rip-Rip/clang_complete/blob/master/README.md
+https://github.com/xavierd/clang_complete/blob/master/README.md
 """
 
 import os
diff --git a/src/crc32c/README.md b/src/crc32c/README.md
index 0bd69f7f097e2..58ba38e611998 100644
--- a/src/crc32c/README.md
+++ b/src/crc32c/README.md
@@ -65,7 +65,7 @@ apm install autocomplete-clang build build-cmake clang-format language-cmake \
 
 If you don't mind more setup in return for more speed, replace
 `autocomplete-clang` and `linter-clang` with `you-complete-me`. This requires
-[setting up ycmd](https://github.com/Valloric/ycmd#building).
+[setting up ycmd](https://github.com/ycm-core/ycmd#building).
 
 ```bash
 apm install autocomplete-plus build build-cmake clang-format language-cmake \
diff --git a/src/crc32c/src/crc32c_arm64_check.h b/src/crc32c/src/crc32c_arm64_check.h
index 62a07aba09c6b..6b80f700377a1 100644
--- a/src/crc32c/src/crc32c_arm64_check.h
+++ b/src/crc32c/src/crc32c_arm64_check.h
@@ -40,7 +40,15 @@ inline bool CanUseArm64Crc32() {
   // From 'arch/arm64/include/uapi/asm/hwcap.h' in Linux kernel source code.
   constexpr unsigned long kHWCAP_PMULL = 1 << 4;
   constexpr unsigned long kHWCAP_CRC32 = 1 << 7;
-  unsigned long hwcap = (&getauxval != nullptr) ? getauxval(AT_HWCAP) : 0;
+  unsigned long hwcap =
+#if HAVE_STRONG_GETAUXVAL
+      // Some compilers warn on (&getauxval != nullptr) in the block below.
+      getauxval(AT_HWCAP);
+#elif HAVE_WEAK_GETAUXVAL
+      (&getauxval != nullptr) ? getauxval(AT_HWCAP) : 0;
+#else
+#error This is supposed to be nested inside a check for HAVE_*_GETAUXVAL.
+#endif  // HAVE_STRONG_GETAUXVAL
   return (hwcap & (kHWCAP_PMULL | kHWCAP_CRC32)) ==
          (kHWCAP_PMULL | kHWCAP_CRC32);
 #elif defined(__APPLE__)
diff --git a/src/fs.cpp b/src/fs.cpp
index f6adf64e2bcf1..9f19dfd52f8e5 100644
--- a/src/fs.cpp
+++ b/src/fs.cpp
@@ -229,7 +229,11 @@ void ofstream::close()
 }
 #else // __GLIBCXX__
 
+#if BOOST_VERSION >= 107700
+static_assert(sizeof(*BOOST_FILESYSTEM_C_STR(fs::path())) == sizeof(wchar_t),
+#else
 static_assert(sizeof(*fs::path().BOOST_FILESYSTEM_C_STR) == sizeof(wchar_t),
+#endif // BOOST_VERSION >= 107700
     "Warning: This build is using boost::filesystem ofstream and ifstream "
     "implementations which will fail to open paths containing multibyte "
     "characters. You should delete this static_assert to ignore this warning, "
diff --git a/src/hash.cpp b/src/hash.cpp
index b54214f8ff1c9..b9d1ef76ad93f 100644
--- a/src/hash.cpp
+++ b/src/hash.cpp
@@ -71,9 +71,6 @@ unsigned int MurmurHash3(unsigned int nHashSeed, Span<const unsigned char> vData
 void BIP32Hash(const ChainCode &chainCode, unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64])
 {
     unsigned char num[4];
-    num[0] = (nChild >> 24) & 0xFF;
-    num[1] = (nChild >> 16) & 0xFF;
-    num[2] = (nChild >>  8) & 0xFF;
-    num[3] = (nChild >>  0) & 0xFF;
+    WriteBE32(num, nChild);
     CHMAC_SHA512(chainCode.begin(), chainCode.size()).Write(&header, 1).Write(data, 32).Write(num, 4).Finalize(output);
 }
diff --git a/src/key.cpp b/src/key.cpp
index 9331ced257731..6aba4578a4adb 100644
--- a/src/key.cpp
+++ b/src/key.cpp
@@ -322,8 +322,7 @@ CExtPubKey CExtKey::Neuter() const {
 void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
     code[0] = nDepth;
     memcpy(code+1, vchFingerprint, 4);
-    code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
-    code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
+    WriteBE32(code+5, nChild);
     memcpy(code+9, chaincode.begin(), 32);
     code[41] = 0;
     assert(key.size() == 32);
@@ -333,7 +332,7 @@ void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
 void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
     nDepth = code[0];
     memcpy(vchFingerprint, code+1, 4);
-    nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
+    nChild = ReadBE32(code+5);
     memcpy(chaincode.begin(), code+9, 32);
     key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
 }
diff --git a/src/key.h b/src/key.h
index 6f88010fc77d3..2c01cd131ef7a 100644
--- a/src/key.h
+++ b/src/key.h
@@ -17,7 +17,6 @@
 
 
 /**
- * secure_allocator is defined in allocators.h
  * CPrivKey is a serialized private key, with all parameters included
  * (SIZE bytes)
  */
diff --git a/src/net.cpp b/src/net.cpp
index 6ddf6ce1f3d4f..bd87764a19df4 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -183,8 +183,8 @@ CAddress GetLocalAddress(const CNetAddr *paddrPeer, ServiceFlags nLocalServices)
 static int GetnScore(const CService& addr)
 {
     LOCK(cs_mapLocalHost);
-    if (mapLocalHost.count(addr) == 0) return 0;
-    return mapLocalHost[addr].nScore;
+    const auto it = mapLocalHost.find(addr);
+    return (it != mapLocalHost.end()) ? it->second.nScore : 0;
 }
 
 // Is our peer's addrLocal potentially useful as an external IP source?
@@ -238,10 +238,10 @@ bool AddLocal(const CService& addr, int nScore)
 
     {
         LOCK(cs_mapLocalHost);
-        bool fAlready = mapLocalHost.count(addr) > 0;
-        LocalServiceInfo &info = mapLocalHost[addr];
-        if (!fAlready || nScore >= info.nScore) {
-            info.nScore = nScore + (fAlready ? 1 : 0);
+        const auto [it, is_newly_added] = mapLocalHost.emplace(addr, LocalServiceInfo());
+        LocalServiceInfo &info = it->second;
+        if (is_newly_added || nScore >= info.nScore) {
+            info.nScore = nScore + (is_newly_added ? 0 : 1);
             info.nPort = addr.GetPort();
         }
     }
@@ -283,12 +283,10 @@ bool IsReachable(const CNetAddr &addr)
 /** vote for a local address */
 bool SeenLocal(const CService& addr)
 {
-    {
-        LOCK(cs_mapLocalHost);
-        if (mapLocalHost.count(addr) == 0)
-            return false;
-        mapLocalHost[addr].nScore++;
-    }
+    LOCK(cs_mapLocalHost);
+    const auto it = mapLocalHost.find(addr);
+    if (it == mapLocalHost.end()) return false;
+    ++it->second.nScore;
     return true;
 }
 
diff --git a/src/pubkey.cpp b/src/pubkey.cpp
index 6744341774f2c..9e7facdc58045 100644
--- a/src/pubkey.cpp
+++ b/src/pubkey.cpp
@@ -253,8 +253,7 @@ bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChi
 void CExtPubKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
     code[0] = nDepth;
     memcpy(code+1, vchFingerprint, 4);
-    code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
-    code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
+    WriteBE32(code+5, nChild);
     memcpy(code+9, chaincode.begin(), 32);
     assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
     memcpy(code+41, pubkey.begin(), CPubKey::COMPRESSED_SIZE);
@@ -263,7 +262,7 @@ void CExtPubKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
 void CExtPubKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
     nDepth = code[0];
     memcpy(vchFingerprint, code+1, 4);
-    nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
+    nChild = ReadBE32(code+5);
     memcpy(chaincode.begin(), code+9, 32);
     pubkey.Set(code+41, code+BIP32_EXTKEY_SIZE);
 }
diff --git a/src/test/fuzz/integer.cpp b/src/test/fuzz/integer.cpp
index b496ab534196e..fbd6ffa995101 100644
--- a/src/test/fuzz/integer.cpp
+++ b/src/test/fuzz/integer.cpp
@@ -95,10 +95,6 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     const unsigned char uch = static_cast<unsigned char>(u8);
     (void)memusage::DynamicUsage(uch);
     (void)MillisToTimeval(i64);
-    const double d = ser_uint64_to_double(u64);
-    assert(ser_double_to_uint64(d) == u64);
-    const float f = ser_uint32_to_float(u32);
-    assert(ser_float_to_uint32(f) == u32);
     (void)SighashToStr(uch);
     (void)SipHashUint256(u64, u64, u256);
     (void)SipHashUint256Extra(u64, u64, u256, u32);
diff --git a/src/util/getuniquepath.cpp b/src/util/getuniquepath.cpp
index 9839d2f6246e5..6776e7785b272 100644
--- a/src/util/getuniquepath.cpp
+++ b/src/util/getuniquepath.cpp
@@ -1,3 +1,7 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 #include <random.h>
 #include <fs.h>
 #include <util/strencodings.h>
diff --git a/src/util/system.cpp b/src/util/system.cpp
index 8f57502ef491e..51b18d2b5cf95 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -1262,7 +1262,7 @@ void SetupEnvironment()
 #endif
     // On most POSIX systems (e.g. Linux, but not BSD) the environment's locale
     // may be invalid, in which case the "C.UTF-8" locale is used as fallback.
-#if !defined(WIN32) && !defined(MAC_OSX) && !defined(__FreeBSD__) && !defined(__OpenBSD__)
+#if !defined(WIN32) && !defined(MAC_OSX) && !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__)
     try {
         std::locale(""); // Raises a runtime error if current locale is invalid
     } catch (const std::runtime_error&) {
diff --git a/src/wallet/test/db_tests.cpp b/src/wallet/test/db_tests.cpp
index 1a020fc35c31d..9d7b47a66f62c 100644
--- a/src/wallet/test/db_tests.cpp
+++ b/src/wallet/test/db_tests.cpp
@@ -18,7 +18,11 @@ BOOST_AUTO_TEST_CASE(getwalletenv_file)
     std::string test_name = "test_name.dat";
     const fs::path datadir = GetDataDir();
     fs::path file_path = datadir / test_name;
+#if BOOST_VERSION >= 107700
+    std::ofstream f(BOOST_FILESYSTEM_C_STR(file_path));
+#else
     std::ofstream f(file_path.BOOST_FILESYSTEM_C_STR);
+#endif // BOOST_VERSION >= 107700
     f.close();
 
     std::string filename;
diff --git a/src/wallet/test/init_test_fixture.cpp b/src/wallet/test/init_test_fixture.cpp
index 86ba0013fe240..9e0190cd9fb91 100644
--- a/src/wallet/test/init_test_fixture.cpp
+++ b/src/wallet/test/init_test_fixture.cpp
@@ -30,7 +30,11 @@ InitWalletDirTestingSetup::InitWalletDirTestingSetup(const std::string& chainNam
     fs::create_directories(m_walletdir_path_cases["default"]);
     fs::create_directories(m_walletdir_path_cases["custom"]);
     fs::create_directories(m_walletdir_path_cases["relative"]);
+#if BOOST_VERSION >= 107700
+    std::ofstream f(BOOST_FILESYSTEM_C_STR(m_walletdir_path_cases["file"]));
+#else
     std::ofstream f(m_walletdir_path_cases["file"].BOOST_FILESYSTEM_C_STR);
+#endif // BOOST_VERSION >= 107700
     f.close();
 }
 
diff --git a/test/README.md b/test/README.md
index eacef7bb40dc4..cd7a523eb71c8 100644
--- a/test/README.md
+++ b/test/README.md
@@ -22,7 +22,7 @@ Before tests can be run locally, Dash Core must be built.  See the [building ins
 
 ### Functional tests
 
-#### Dependencies
+#### Dependencies and prerequisites
 
 Many Dash specific tests require dash_hash. To install it:
 
@@ -34,6 +34,13 @@ The ZMQ functional test requires a python ZMQ library. To install it:
 - on Unix, run `sudo apt-get install python3-zmq`
 - on mac OS, run `pip3 install pyzmq`
 
+
+On Windows the `PYTHONUTF8` environment variable must be set to 1:
+
+```cmd
+set PYTHONUTF8=1
+```
+
 #### Running the tests
 
 Individual tests can be run by directly calling the test script, e.g.:
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 8e35753bc7850..58ad799b2c1c4 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -316,8 +316,9 @@ def main():
         for test in tests:
             script = test.split("/")[-1]
             script = script + ".py" if ".py" not in script else script
-            if script in ALL_SCRIPTS:
-                test_list.append(script)
+            matching_scripts = [s for s in ALL_SCRIPTS if s.startswith(script)]
+            if matching_scripts:
+                test_list.extend(matching_scripts)
             else:
                 print("{}WARNING!{} Test '{}' not found in full test list.".format(BOLD[1], BOLD[0], test))
     elif args.extended: