diff --git a/.github/workflows/dev-builds.yaml b/.github/workflows/dev-builds.yaml
index 1e354b982f..dc1ec6600b 100644
--- a/.github/workflows/dev-builds.yaml
+++ b/.github/workflows/dev-builds.yaml
@@ -94,10 +94,10 @@ jobs:
     - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
 
     - name: Build and package
-      run: TARGETS="x86_64-apple-darwin11" ./make.sh docker-release-git
+      run: TARGETS="x86_64-apple-darwin18" ./make.sh docker-release-git
 
-    - name: Publish artifact - x86_64-apple-darwin11
+    - name: Publish artifact - x86_64-apple-darwin18
       uses: actions/upload-artifact@e448a9b857ee2131e752b06002bf0e093c65e571
       with:
-        name: defichain-${{ env.BUILD_VERSION }}-x86_64-apple-darwin11
-        path: ./build/defichain-${{ env.BUILD_VERSION }}-x86_64-apple-darwin11.tar.gz
+        name: defichain-${{ env.BUILD_VERSION }}-x86_64-apple-darwin18
+        path: ./build/defichain-${{ env.BUILD_VERSION }}-x86_64-apple-darwin18.tar.gz
diff --git a/build-aux/m4/ax_cxx_compile_stdcxx.m4 b/build-aux/m4/ax_cxx_compile_stdcxx.m4
index f147cee3b1..f0a3badf59 100644
--- a/build-aux/m4/ax_cxx_compile_stdcxx.m4
+++ b/build-aux/m4/ax_cxx_compile_stdcxx.m4
@@ -45,9 +45,9 @@ dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
 dnl  (serial version number 13).
 
 AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
-  m4_if([$1], [11], [],
-        [$1], [14], [],
-        [$1], [17], [m4_fatal([support for C++17 not yet implemented in AX_CXX_COMPILE_STDCXX])],
+  m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
+        [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
+        [$1], [17], [ax_cxx_compile_alternatives="17 1z"],
         [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
   m4_if([$2], [], [],
         [$2], [ext], [],
@@ -57,26 +57,13 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
         [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
         [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
         [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
-  m4_if([$4], [], [ax_cxx_compile_cxx$1_try_default=true],
-        [$4], [default], [ax_cxx_compile_cxx$1_try_default=true],
-        [$4], [nodefault], [ax_cxx_compile_cxx$1_try_default=false],
-        [m4_fatal([invalid fourth argument `$4' to AX_CXX_COMPILE_STDCXX])])
   AC_LANG_PUSH([C++])dnl
   ac_success=no
 
-  m4_if([$4], [nodefault], [], [dnl
-  AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
-  ax_cv_cxx_compile_cxx$1,
-  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
-    [ax_cv_cxx_compile_cxx$1=yes],
-    [ax_cv_cxx_compile_cxx$1=no])])
-  if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
-    ac_success=yes
-  fi])
-
   m4_if([$2], [noext], [], [dnl
   if test x$ac_success = xno; then
-    for switch in -std=gnu++$1 -std=gnu++0x; do
+    for alternative in ${ax_cxx_compile_alternatives}; do
+      switch="-std=gnu++${alternative}"
       cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
       AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
                      $cachevar,
@@ -102,22 +89,27 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
     dnl HP's aCC needs +std=c++11 according to:
     dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
     dnl Cray's crayCC needs "-h std=c++11"
-    for switch in -std=c++$1 -std=c++0x +std=c++$1 "-h std=c++$1"; do
-      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
-      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
-                     $cachevar,
-        [ac_save_CXX="$CXX"
-         CXX="$CXX $switch"
-         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
-          [eval $cachevar=yes],
-          [eval $cachevar=no])
-         CXX="$ac_save_CXX"])
-      if eval test x\$$cachevar = xyes; then
-        CXX="$CXX $switch"
-        if test -n "$CXXCPP" ; then
-          CXXCPP="$CXXCPP $switch"
+    for alternative in ${ax_cxx_compile_alternatives}; do
+      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
+        cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
+        AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+                       $cachevar,
+          [ac_save_CXX="$CXX"
+           CXX="$CXX $switch"
+           AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+            [eval $cachevar=yes],
+            [eval $cachevar=no])
+           CXX="$ac_save_CXX"])
+        if eval test x\$$cachevar = xyes; then
+          CXX="$CXX $switch"
+          if test -n "$CXXCPP" ; then
+            CXXCPP="$CXXCPP $switch"
+          fi
+          ac_success=yes
+          break
         fi
-        ac_success=yes
+      done
+      if test x$ac_success = xyes; then
         break
       fi
     done
@@ -154,6 +146,11 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
   _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
 )
 
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
+)
 
 dnl  Tests for new features in C++11
 
@@ -191,11 +188,13 @@ namespace cxx11
 
     struct Base
     {
+      virtual ~Base() {}
       virtual void f() {}
     };
 
     struct Derived : public Base
     {
+      virtual ~Derived() override {}
       virtual void f() override {}
     };
 
@@ -524,7 +523,7 @@ namespace cxx14
 
   }
 
-  namespace test_digit_seperators
+  namespace test_digit_separators
   {
 
     constexpr auto ten_million = 100'000'000;
@@ -566,3 +565,287 @@ namespace cxx14
 #endif  // __cplusplus >= 201402L
 
 ]])
+
+
+dnl  Tests for new features in C++17
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
+// If the compiler admits that it is not ready for C++17, why torture it?
+// Hopefully, this will speed up the test.
+#ifndef __cplusplus
+#error "This is not a C++ compiler"
+#elif __cplusplus < 201703L
+#error "This is not a C++17 compiler"
+#else
+#include <initializer_list>
+#include <utility>
+#include <type_traits>
+namespace cxx17
+{
+  namespace test_constexpr_lambdas
+  {
+    constexpr int foo = [](){return 42;}();
+  }
+  namespace test::nested_namespace::definitions
+  {
+  }
+  namespace test_fold_expression
+  {
+    template<typename... Args>
+    int multiply(Args... args)
+    {
+      return (args * ... * 1);
+    }
+    template<typename... Args>
+    bool all(Args... args)
+    {
+      return (args && ...);
+    }
+  }
+  namespace test_extended_static_assert
+  {
+    static_assert (true);
+  }
+  namespace test_auto_brace_init_list
+  {
+    auto foo = {5};
+    auto bar {5};
+    static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
+    static_assert(std::is_same<int, decltype(bar)>::value);
+  }
+  namespace test_typename_in_template_template_parameter
+  {
+    template<template<typename> typename X> struct D;
+  }
+  namespace test_fallthrough_nodiscard_maybe_unused_attributes
+  {
+    int f1()
+    {
+      return 42;
+    }
+    [[nodiscard]] int f2()
+    {
+      [[maybe_unused]] auto unused = f1();
+      switch (f1())
+      {
+      case 17:
+        f1();
+        [[fallthrough]];
+      case 42:
+        f1();
+      }
+      return f1();
+    }
+  }
+  namespace test_extended_aggregate_initialization
+  {
+    struct base1
+    {
+      int b1, b2 = 42;
+    };
+    struct base2
+    {
+      base2() {
+        b3 = 42;
+      }
+      int b3;
+    };
+    struct derived : base1, base2
+    {
+        int d;
+    };
+    derived d1 {{1, 2}, {}, 4};  // full initialization
+    derived d2 {{}, {}, 4};      // value-initialized bases
+  }
+  namespace test_general_range_based_for_loop
+  {
+    struct iter
+    {
+      int i;
+      int& operator* ()
+      {
+        return i;
+      }
+      const int& operator* () const
+      {
+        return i;
+      }
+      iter& operator++()
+      {
+        ++i;
+        return *this;
+      }
+    };
+    struct sentinel
+    {
+      int i;
+    };
+    bool operator== (const iter& i, const sentinel& s)
+    {
+      return i.i == s.i;
+    }
+    bool operator!= (const iter& i, const sentinel& s)
+    {
+      return !(i == s);
+    }
+    struct range
+    {
+      iter begin() const
+      {
+        return {0};
+      }
+      sentinel end() const
+      {
+        return {5};
+      }
+    };
+    void f()
+    {
+      range r {};
+      for (auto i : r)
+      {
+        [[maybe_unused]] auto v = i;
+      }
+    }
+  }
+  namespace test_lambda_capture_asterisk_this_by_value
+  {
+    struct t
+    {
+      int i;
+      int foo()
+      {
+        return [*this]()
+        {
+          return i;
+        }();
+      }
+    };
+  }
+  namespace test_enum_class_construction
+  {
+    enum class byte : unsigned char
+    {};
+    byte foo {42};
+  }
+  namespace test_constexpr_if
+  {
+    template <bool cond>
+    int f ()
+    {
+      if constexpr(cond)
+      {
+        return 13;
+      }
+      else
+      {
+        return 42;
+      }
+    }
+  }
+  namespace test_selection_statement_with_initializer
+  {
+    int f()
+    {
+      return 13;
+    }
+    int f2()
+    {
+      if (auto i = f(); i > 0)
+      {
+        return 3;
+      }
+      switch (auto i = f(); i + 4)
+      {
+      case 17:
+        return 2;
+      default:
+        return 1;
+      }
+    }
+  }
+  namespace test_template_argument_deduction_for_class_templates
+  {
+    template <typename T1, typename T2>
+    struct pair
+    {
+      pair (T1 p1, T2 p2)
+        : m1 {p1},
+          m2 {p2}
+      {}
+      T1 m1;
+      T2 m2;
+    };
+    void f()
+    {
+      [[maybe_unused]] auto p = pair{13, 42u};
+    }
+  }
+  namespace test_non_type_auto_template_parameters
+  {
+    template <auto n>
+    struct B
+    {};
+    B<5> b1;
+    B<'a'> b2;
+  }
+  namespace test_structured_bindings
+  {
+    int arr[2] = { 1, 2 };
+    std::pair<int, int> pr = { 1, 2 };
+    auto f1() -> int(&)[2]
+    {
+      return arr;
+    }
+    auto f2() -> std::pair<int, int>&
+    {
+      return pr;
+    }
+    struct S
+    {
+      int x1 : 2;
+      volatile double y1;
+    };
+    S f3()
+    {
+      return {};
+    }
+    auto [ x1, y1 ] = f1();
+    auto& [ xr1, yr1 ] = f1();
+    auto [ x2, y2 ] = f2();
+    auto& [ xr2, yr2 ] = f2();
+    const auto [ x3, y3 ] = f3();
+  }
+  namespace test_exception_spec_type_system
+  {
+    struct Good {};
+    struct Bad {};
+    void g1() noexcept;
+    void g2();
+    template<typename T>
+    Bad
+    f(T*, T*);
+    template<typename T1, typename T2>
+    Good
+    f(T1*, T2*);
+    static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
+  }
+  namespace test_inline_variables
+  {
+    template<class T> void f(T)
+    {}
+    template<class T> inline T g(T)
+    {
+      return T{};
+    }
+    template<> inline void f<>(int)
+    {}
+    template<> int g<>(int)
+    {
+      return 5;
+    }
+  }
+}  // namespace cxx17
+#endif  // __cplusplus < 201703L
+]])
+
diff --git a/ci/test/00_setup_env_mac.sh b/ci/test/00_setup_env_mac.sh
index 1da55be1dd..e6bfbd6169 100644
--- a/ci/test/00_setup_env_mac.sh
+++ b/ci/test/00_setup_env_mac.sh
@@ -6,9 +6,10 @@
 
 export LC_ALL=C.UTF-8
 
-export HOST=x86_64-apple-darwin14
+export HOST=x86_64-apple-darwin18
 export PACKAGES="cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python3-dev python3-setuptools"
-export OSX_SDK=10.11
+export XCODE_VERSION=11.3.1
+export XCODE_BUILD_ID=11C505
 export RUN_UNIT_TESTS=false
 export RUN_FUNCTIONAL_TESTS=false
 export GOAL="deploy"
diff --git a/ci/test/05_before_script.sh b/ci/test/05_before_script.sh
index 202b7ef3b7..7b97902919 100755
--- a/ci/test/05_before_script.sh
+++ b/ci/test/05_before_script.sh
@@ -10,11 +10,14 @@ DOCKER_EXEC echo \> \$HOME/.defi  # Make sure default datadir does not exist and
 
 mkdir -p depends/SDKs depends/sdk-sources
 
-if [ -n "$OSX_SDK" ] && [ ! -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then
-  curl --location --fail $SDK_URL/MacOSX${OSX_SDK}.sdk.tar.gz -o depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz
+OSX_SDK_BASENAME="Xcode-${XCODE_VERSION}-${XCODE_BUILD_ID}-extracted-SDK-with-libcxx-headers.tar.gz"
+OSX_SDK_PATH="${DEPENDS_DIR}/sdk-sources/${OSX_SDK_BASENAME}"
+
+if [ -n "$XCODE_VERSION" ] && [ ! -f "$OSX_SDK_PATH" ]; then
+  curl --location --fail "${SDK_URL}/${OSX_SDK_BASENAME}" -o "$OSX_SDK_PATH"
 fi
-if [ -n "$OSX_SDK" ] && [ -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then
-  tar -C depends/SDKs -xf depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz
+if [ -n "$XCODE_VERSION" ] && [ -f "$OSX_SDK_PATH" ]; then
+  DOCKER_EXEC tar -C "${DEPENDS_DIR}/SDKs" -xf "$OSX_SDK_PATH"
 fi
 if [[ $HOST = *-mingw32 ]]; then
   DOCKER_EXEC update-alternatives --set $HOST-g++ \$\(which $HOST-g++-posix\)
diff --git a/configure.ac b/configure.ac
index 9003810b30..2b50c0fe9d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -61,8 +61,10 @@ case $host in
      lt_cv_deplibs_check_method="pass_all"
   ;;
 esac
-dnl Require C++11 compiler (no GNU extensions)
-AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory], [nodefault])
+
+dnl Require C++17 compiler (no GNU extensions)
+AX_CXX_COMPILE_STDCXX([17], [noext], [mandatory])
+
 dnl Check if -latomic is required for <std::atomic>
 CHECK_ATOMIC
 
diff --git a/contrib/dockerfiles/x86_64-apple-darwin11.dockerfile b/contrib/dockerfiles/x86_64-apple-darwin18.dockerfile
similarity index 98%
rename from contrib/dockerfiles/x86_64-apple-darwin11.dockerfile
rename to contrib/dockerfiles/x86_64-apple-darwin18.dockerfile
index 48aba70193..850e63b9d1 100644
--- a/contrib/dockerfiles/x86_64-apple-darwin11.dockerfile
+++ b/contrib/dockerfiles/x86_64-apple-darwin18.dockerfile
@@ -1,4 +1,4 @@
-ARG TARGET=x86_64-apple-darwin11
+ARG TARGET=x86_64-apple-darwin18
 
 # -----------
 FROM ubuntu:18.04 as builder-base
diff --git a/depends/README.md b/depends/README.md
index 69bc2a0222..e18ba57967 100644
--- a/depends/README.md
+++ b/depends/README.md
@@ -25,7 +25,7 @@ Common `host-platform-triplets` for cross compilation are:
 - `i686-pc-linux-gnu` for Linux 32 bit
 - `x86_64-pc-linux-gnu` for x86 Linux
 - `x86_64-w64-mingw32` for Win64
-- `x86_64-apple-darwin14` for macOS
+- `x86_64-apple-darwin18` for macOS
 - `arm-linux-gnueabihf` for Linux ARM 32 bit
 - `aarch64-linux-gnu` for Linux ARM 64 bit
 - `riscv32-linux-gnu` for Linux RISC-V 32 bit
diff --git a/depends/hosts/darwin.mk b/depends/hosts/darwin.mk
index a1c943d60b..b14ce09cb8 100644
--- a/depends/hosts/darwin.mk
+++ b/depends/hosts/darwin.mk
@@ -1,7 +1,10 @@
-OSX_MIN_VERSION=10.10
-OSX_SDK_VERSION=10.11
-OSX_SDK=$(SDK_PATH)/MacOSX$(OSX_SDK_VERSION).sdk
-LD64_VERSION=253.9
+OSX_MIN_VERSION=10.14
+OSX_SDK_VERSION=10.15.1
+XCODE_VERSION=11.3.1
+XCODE_BUILD_ID=11C505
+OSX_SDK=$(SDK_PATH)/Xcode-$(XCODE_VERSION)-$(XCODE_BUILD_ID)-extracted-SDK-with-libcxx-headers
+LD64_VERSION=530
+
 darwin_CC=clang -target $(host) -mmacosx-version-min=$(OSX_MIN_VERSION) --sysroot $(OSX_SDK) -mlinker-version=$(LD64_VERSION)
 darwin_CXX=clang++ -target $(host) -mmacosx-version-min=$(OSX_MIN_VERSION) --sysroot $(OSX_SDK) -mlinker-version=$(LD64_VERSION) -stdlib=libc++
 
diff --git a/depends/packages/bdb.mk b/depends/packages/bdb.mk
index 6cdb79592b..f983c754ab 100644
--- a/depends/packages/bdb.mk
+++ b/depends/packages/bdb.mk
@@ -9,7 +9,7 @@ define $(package)_set_vars
 $(package)_config_opts=--disable-shared --enable-cxx --disable-replication
 $(package)_config_opts_mingw32=--enable-mingw
 $(package)_config_opts_linux=--with-pic
-$(package)_cxxflags=-std=c++11
+$(package)_cxxflags=-std=c++17
 $(package)_cppflags_mingw32=-DUNICODE -D_UNICODE
 endef
 
diff --git a/depends/packages/boost.mk b/depends/packages/boost.mk
index c84c5d0ab1..ad25069f51 100644
--- a/depends/packages/boost.mk
+++ b/depends/packages/boost.mk
@@ -20,7 +20,7 @@ $(package)_archiver_$(host_os)=$($(package)_ar)
 $(package)_toolset_darwin=darwin
 $(package)_archiver_darwin=$($(package)_libtool)
 $(package)_config_libraries=chrono,filesystem,system,thread,test
-$(package)_cxxflags=-std=c++11 -fvisibility=hidden
+$(package)_cxxflags=-std=c++17 -fvisibility=hidden
 $(package)_cxxflags_linux=-fPIC
 endef
 
diff --git a/depends/packages/native_cctools.mk b/depends/packages/native_cctools.mk
index a065256c1c..74c32c4e38 100644
--- a/depends/packages/native_cctools.mk
+++ b/depends/packages/native_cctools.mk
@@ -1,45 +1,55 @@
 package=native_cctools
-$(package)_version=807d6fd1be5d2224872e381870c0a75387fe05e6
-$(package)_download_path=https://github.com/theuni/cctools-port/archive
+$(package)_version=4da2f3b485bcf4cef526f30c0b8c0bcda99cdbb4
+$(package)_download_path=https://github.com/tpoechtrager/cctools-port/archive
 $(package)_file_name=$($(package)_version).tar.gz
-$(package)_sha256_hash=a09c9ba4684670a0375e42d9d67e7f12c1f62581a27f28f7c825d6d7032ccc6a
+$(package)_sha256_hash=a2d491c0981cef72fee2b833598f20f42a6c44a7614a61c439bda93d56446fec
 $(package)_build_subdir=cctools
-$(package)_clang_version=3.7.1
-$(package)_clang_download_path=https://llvm.org/releases/$($(package)_clang_version)
+$(package)_clang_version=8.0.0
+$(package)_clang_download_path=https://releases.llvm.org/$($(package)_clang_version)
 $(package)_clang_download_file=clang+llvm-$($(package)_clang_version)-x86_64-linux-gnu-ubuntu-14.04.tar.xz
 $(package)_clang_file_name=clang-llvm-$($(package)_clang_version)-x86_64-linux-gnu-ubuntu-14.04.tar.xz
-$(package)_clang_sha256_hash=99b28a6b48e793705228a390471991386daa33a9717cd9ca007fcdde69608fd9
+$(package)_clang_sha256_hash=9ef854b71949f825362a119bf2597f744836cb571131ae6b721cd102ffea8cd0
+
+$(package)_libtapi_version=3efb201881e7a76a21e0554906cf306432539cef
+$(package)_libtapi_download_path=https://github.com/tpoechtrager/apple-libtapi/archive
+$(package)_libtapi_download_file=$($(package)_libtapi_version).tar.gz
+$(package)_libtapi_file_name=$($(package)_libtapi_version).tar.gz
+$(package)_libtapi_sha256_hash=380c1ca37cfa04a8699d0887a8d3ee1ad27f3d08baba78887c73b09485c0fbd3
+
 $(package)_extra_sources=$($(package)_clang_file_name)
+$(package)_extra_sources += $($(package)_libtapi_file_name)
 
 define $(package)_fetch_cmds
 $(call fetch_file,$(package),$($(package)_download_path),$($(package)_download_file),$($(package)_file_name),$($(package)_sha256_hash)) && \
-$(call fetch_file,$(package),$($(package)_clang_download_path),$($(package)_clang_download_file),$($(package)_clang_file_name),$($(package)_clang_sha256_hash))
+$(call fetch_file,$(package),$($(package)_clang_download_path),$($(package)_clang_download_file),$($(package)_clang_file_name),$($(package)_clang_sha256_hash)) && \
+$(call fetch_file,$(package),$($(package)_libtapi_download_path),$($(package)_libtapi_download_file),$($(package)_libtapi_file_name),$($(package)_libtapi_sha256_hash))
 endef
 
 define $(package)_extract_cmds
   mkdir -p $($(package)_extract_dir) && \
   echo "$($(package)_sha256_hash)  $($(package)_source)" > $($(package)_extract_dir)/.$($(package)_file_name).hash && \
   echo "$($(package)_clang_sha256_hash)  $($(package)_source_dir)/$($(package)_clang_file_name)" >> $($(package)_extract_dir)/.$($(package)_file_name).hash && \
+  echo "$($(package)_libtapi_sha256_hash)  $($(package)_source_dir)/$($(package)_libtapi_file_name)" >> $($(package)_extract_dir)/.$($(package)_file_name).hash && \
   $(build_SHA256SUM) -c $($(package)_extract_dir)/.$($(package)_file_name).hash && \
-  mkdir -p toolchain/bin toolchain/lib/clang/3.5/include && \
+  mkdir -p toolchain/bin toolchain/lib/clang/$($(package)_clang_version)/include && \
+  mkdir -p libtapi && \
+  tar --no-same-owner --strip-components=1 -C libtapi -xf $($(package)_source_dir)/$($(package)_libtapi_file_name) && \
   tar --no-same-owner --strip-components=1 -C toolchain -xf $($(package)_source_dir)/$($(package)_clang_file_name) && \
   rm -f toolchain/lib/libc++abi.so* && \
-  echo "#!/bin/sh" > toolchain/bin/$(host)-dsymutil && \
-  echo "exit 0" >> toolchain/bin/$(host)-dsymutil && \
-  chmod +x toolchain/bin/$(host)-dsymutil && \
   tar --no-same-owner --strip-components=1 -xf $($(package)_source)
 endef
 
 define $(package)_set_vars
-$(package)_config_opts=--target=$(host) --disable-lto-support
-$(package)_ldflags+=-Wl,-rpath=\\$$$$$$$$\$$$$$$$$ORIGIN/../lib
-$(package)_cc=$($(package)_extract_dir)/toolchain/bin/clang
-$(package)_cxx=$($(package)_extract_dir)/toolchain/bin/clang++
+  $(package)_config_opts=--target=$(host) --disable-lto-support --with-libtapi=$($(package)_extract_dir)
+  $(package)_ldflags+=-Wl,-rpath=\\$$$$$$$$\$$$$$$$$ORIGIN/../lib
+  $(package)_cc=$($(package)_extract_dir)/toolchain/bin/clang
+  $(package)_cxx=$($(package)_extract_dir)/toolchain/bin/clang++
 endef
 
 define $(package)_preprocess_cmds
-  cd $($(package)_build_subdir); ./autogen.sh && \
-  sed -i.old "/define HAVE_PTHREADS/d" ld64/src/ld/InputFiles.h
+  CC=$($(package)_cc) CXX=$($(package)_cxx) INSTALLPREFIX=$($(package)_extract_dir) ./libtapi/build.sh && \
+  CC=$($(package)_cc) CXX=$($(package)_cxx) INSTALLPREFIX=$($(package)_extract_dir) ./libtapi/install.sh && \
+  sed -i.old "/define HAVE_PTHREADS/d" $($(package)_build_subdir)/ld64/src/ld/InputFiles.h
 endef
 
 define $(package)_config_cmds
@@ -52,6 +62,9 @@ endef
 
 define $(package)_stage_cmds
   $(MAKE) DESTDIR=$($(package)_staging_dir) install && \
+  mkdir -p $($(package)_staging_prefix_dir)/lib/ && \
+  cd $($(package)_extract_dir) && \
+  cp lib/libtapi.so.6 $($(package)_staging_prefix_dir)/lib/ && \
   cd $($(package)_extract_dir)/toolchain && \
   mkdir -p $($(package)_staging_prefix_dir)/lib/clang/$($(package)_clang_version)/include && \
   mkdir -p $($(package)_staging_prefix_dir)/bin $($(package)_staging_prefix_dir)/include && \
@@ -59,7 +72,6 @@ define $(package)_stage_cmds
   cp -P bin/clang++ $($(package)_staging_prefix_dir)/bin/ &&\
   cp lib/libLTO.so $($(package)_staging_prefix_dir)/lib/ && \
   cp -rf lib/clang/$($(package)_clang_version)/include/* $($(package)_staging_prefix_dir)/lib/clang/$($(package)_clang_version)/include/ && \
-  cp bin/llvm-dsymutil $($(package)_staging_prefix_dir)/bin/$(host)-dsymutil && \
-  if `test -d include/c++/`; then cp -rf include/c++/ $($(package)_staging_prefix_dir)/include/; fi && \
-  if `test -d lib/c++/`; then cp -rf lib/c++/ $($(package)_staging_prefix_dir)/lib/; fi
+  cp bin/dsymutil $($(package)_staging_prefix_dir)/bin/$(host)-dsymutil
 endef
+
diff --git a/depends/packages/zeromq.mk b/depends/packages/zeromq.mk
index 9ac037ebb5..f9b26a1bf3 100644
--- a/depends/packages/zeromq.mk
+++ b/depends/packages/zeromq.mk
@@ -10,7 +10,7 @@ define $(package)_set_vars
   $(package)_config_opts += --without-libsodium --without-libgssapi_krb5 --without-pgm --without-norm --without-vmci
   $(package)_config_opts += --disable-libunwind --disable-radix-tree --without-gcov
   $(package)_config_opts_linux=--with-pic
-  $(package)_cxxflags=-std=c++11
+  $(package)_cxxflags=-std=c++17
 endef
 
 define $(package)_preprocess_cmds
diff --git a/doc/dependencies.md b/doc/dependencies.md
index 70bc5e6ed3..e0f13c9a59 100644
--- a/doc/dependencies.md
+++ b/doc/dependencies.md
@@ -7,11 +7,11 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | --- | --- | --- | --- | --- | --- |
 | Berkeley DB | [4.8.30](https://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html) | 4.8.x | No |  |  |
 | Boost | [1.70.0](https://www.boost.org/users/download/) | [1.47.0](https://github.com/bitcoin/bitcoin/pull/8920) | No |  |  |
-| Clang |  | [3.3+](https://releases.llvm.org/download.html) (C++11 support) |  |  |  |
+| Clang |  | [5.0+](https://releases.llvm.org/download.html) (C++17 support) |  |  |  |
 | Expat | [2.2.7](https://libexpat.github.io/) |  | No | Yes |  |
 | fontconfig | [2.12.1](https://www.freedesktop.org/software/fontconfig/release/) |  | No | Yes |  |
 | FreeType | [2.7.1](https://download.savannah.gnu.org/releases/freetype) |  | No |  |  |
-| GCC |  | [4.8+](https://gcc.gnu.org/) (C++11 support) |  |  |  |
+| GCC |  | [7+](https://gcc.gnu.org/) (C++17 support) |  |  |  |
 | HarfBuzz-NG |  |  |  |  |  |
 | libevent | [2.1.8-stable](https://github.com/libevent/libevent/releases) | 2.0.22 | No |  |  |
 | libpng |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) |
diff --git a/make.sh b/make.sh
index 143cf58888..d12df1972f 100755
--- a/make.sh
+++ b/make.sh
@@ -28,7 +28,7 @@ setup_vars() {
 
     # shellcheck disable=SC2206
     # This intentionally word-splits the array as env arg can only be strings.
-    # Other options available: x86_64-w64-mingw32 x86_64-apple-darwin11
+    # Other options available: x86_64-w64-mingw32 x86_64-apple-darwin18
     TARGETS=(${TARGETS:-"x86_64-pc-linux-gnu"})
 }
 
@@ -193,7 +193,7 @@ docker_build() {
     echo "> docker-build";
 
     for target in "${targets[@]}"; do
-        if [[ "$target" == "x86_64-apple-darwin11" ]]; then
+        if [[ "$target" == "x86_64-apple-darwin18" ]]; then
             pkg_ensure_mac_sdk
         fi
         local img="${img_prefix}-${target}:${img_version}"
@@ -385,8 +385,8 @@ pkg_install_llvm() {
 }
 
 pkg_ensure_mac_sdk() {
-    local sdk_name="MacOSX10.11.sdk"
-    local pkg="${sdk_name}.tar.xz"
+    local sdk_name="Xcode-11.3.1-11C505-extracted-SDK-with-libcxx-headers"
+    local pkg="${sdk_name}.tar.gz"
 
     echo "> ensuring mac sdk"
 
@@ -394,9 +394,9 @@ pkg_ensure_mac_sdk() {
     pushd ./depends/SDKs >/dev/null
     if [[ ! -d "$sdk_name" ]]; then
         if [[ ! -f "${pkg}" ]]; then
-            wget https://github.com/phracker/MacOSX-SDKs/releases/download/10.15/MacOSX10.11.sdk.tar.xz
+            wget https://bitcoincore.org/depends-sources/sdks/Xcode-11.3.1-11C505-extracted-SDK-with-libcxx-headers.tar.gz
         fi
-        tar -xvf "${pkg}"
+        tar -zxvf "${pkg}"
     fi
     rm "${pkg}" 2>/dev/null || true
     popd >/dev/null
diff --git a/src/span.h b/src/span.h
index 594dd0c241..d1ba93fb11 100644
--- a/src/span.h
+++ b/src/span.h
@@ -24,6 +24,23 @@ class Span
     constexpr Span(C* data, std::ptrdiff_t size) noexcept : m_data(data), m_size(size) {}
     constexpr Span(C* data, C* end) noexcept : m_data(data), m_size(end - data) {}
 
+    /** Implicit conversion of spans between compatible types.
+     *
+     *  Specifically, if a pointer to an array of type O can be implicitly converted to a pointer to an array of type
+     *  C, then permit implicit conversion of Span<O> to Span<C>. This matches the behavior of the corresponding
+     *  C++20 std::span constructor.
+     *
+     *  For example this means that a Span<T> can be converted into a Span<const T>.
+     */
+    template <typename O, typename std::enable_if<std::is_convertible<O (*)[], C (*)[]>::value, int>::type = 0>
+    constexpr Span(const Span<O>& other) noexcept : m_data(other.m_data), m_size(other.m_size) {}
+
+    /** Default copy constructor. */
+    constexpr Span(const Span&) noexcept = default;
+
+    /** Default assignment operator. */
+    Span& operator=(const Span& other) noexcept = default;
+
     constexpr C* data() const noexcept { return m_data; }
     constexpr C* begin() const noexcept { return m_data; }
     constexpr C* end() const noexcept { return m_data + m_size; }
@@ -41,6 +58,8 @@ class Span
     friend constexpr bool operator<=(const Span& a, const Span& b) noexcept { return !(b < a); }
     friend constexpr bool operator>(const Span& a, const Span& b) noexcept { return (b < a); }
     friend constexpr bool operator>=(const Span& a, const Span& b) noexcept { return !(a < b); }
+
+    template <typename O> friend class Span;
 };
 
 /** Create a span to a container exposing data() and size().