Merge #20413: build: Require C++17 compiler

fac71987281077aed7f79dce99f4eb3e8a91916a Use std::make_unique (MarcoFalke)
faaee810e62d796d66bfb2bc4e53c8b4c8104d13 build: Require C++17 compiler (MarcoFalke)

Pull request description:

  Developers have been compiling with C++17 for a few months now (fuzz tests and the msvc build have it even enabled by default). According to #16684, the 22.0 release shall be compiled with C++17 enabled.

  This only sets the build flag, any other changes need more discussion and can be done later.

ACKs for top commit:
  elichai:
    utACK fac71987281077aed7f79dce99f4eb3e8a91916a
  hebasto:
    ACK fac71987281077aed7f79dce99f4eb3e8a91916a, I've locally compiled on ARM 32bit SBC without GUI.
  fanquake:
    ACK fac71987281077aed7f79dce99f4eb3e8a91916a

Tree-SHA512: 53eb40ba5d496376a2d2cf16e2000bef36616cc2a3696c3ec59a5366e41fa8b872817a7ca21751f030f9c1efb339dfa63cc655eaa5199b9a3d2e52c2de0ccb29

8 files changed, 19 insertions, 27 deletions

diff --git a/.travis.yml b/.travis.yml
index bb5e0a854c..780bc9944f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -66,7 +66,7 @@ jobs:
         - set -o errexit; source ./ci/lint/06_script.sh
 
     - stage: test
-      name: '32-bit + dash  [GOAL: install]  [CentOS 7]  [gui]'
+      name: '32-bit + dash  [GOAL: install]  [CentOS 8]  [gui]'
       env: >-
         FILE_ENV="./ci/test/00_setup_env_i686_centos.sh"
 
diff --git a/ci/test/00_setup_env_i686_centos.sh b/ci/test/00_setup_env_i686_centos.sh
index e58003ab19..52cdb75a0c 100644
--- a/ci/test/00_setup_env_i686_centos.sh
+++ b/ci/test/00_setup_env_i686_centos.sh
@@ -7,9 +7,10 @@
 export LC_ALL=C.UTF-8
 
 export HOST=i686-pc-linux-gnu
-export CONTAINER_NAME=ci_i686_centos_7
-export DOCKER_NAME_TAG=centos:7
-export DOCKER_PACKAGES="gcc-c++ glibc-devel.x86_64 libstdc++-devel.x86_64 glibc-devel.i686 libstdc++-devel.i686 ccache libtool make git python3 python36-zmq which patch lbzip2 dash"
+export CONTAINER_NAME=ci_i686_centos_8
+export DOCKER_NAME_TAG=centos:8
+export DOCKER_PACKAGES="gcc-c++ glibc-devel.x86_64 libstdc++-devel.x86_64 glibc-devel.i686 libstdc++-devel.i686 ccache libtool make git python3 python3-zmq which patch lbzip2 dash rsync coreutils"
 export GOAL="install"
-export BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-reduce-exports --with-boost-process"
+export DEP_OPTS="NO_QT=1"  # Gui disabled for now to avoid build failures
+export BITCOIN_CONFIG="--enable-zmq --with-gui=no --enable-reduce-exports --with-boost-process"
 export CONFIG_SHELL="/bin/dash"
diff --git a/ci/test/00_setup_env_native_nowallet.sh b/ci/test/00_setup_env_native_nowallet.sh
index 0fe7d35435..7ff044c020 100644
--- a/ci/test/00_setup_env_native_nowallet.sh
+++ b/ci/test/00_setup_env_native_nowallet.sh
@@ -7,8 +7,8 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_native_nowallet
-export DOCKER_NAME_TAG=ubuntu:18.04  # Use bionic to have one config run the tests in python3.6, see doc/dependencies.md (3.6 is not available in xenial/16.04)
-export PACKAGES="python3-zmq clang-3.9 llvm-3.9"  # Use clang-3.9 to test C++11 compatibility, see doc/dependencies.md (3.8 is not available in bionic)
+export DOCKER_NAME_TAG=ubuntu:18.04  # Use bionic to have one config run the tests in python3.6, see doc/dependencies.md
+export PACKAGES="python3-zmq clang-5.0 llvm-5.0"  # Use clang-5 to test C++17 compatibility, see doc/dependencies.md
 export DEP_OPTS="NO_WALLET=1"
 export GOAL="install"
-export BITCOIN_CONFIG="--enable-glibc-back-compat --enable-reduce-exports CC=clang-3.9 CXX=clang++-3.9 --with-boost-process"
+export BITCOIN_CONFIG="--enable-glibc-back-compat --enable-reduce-exports CC=clang-5.0 CXX=clang++-5.0 --with-boost-process"
diff --git a/ci/test/00_setup_env_native_qt5.sh b/ci/test/00_setup_env_native_qt5.sh
index 8668662299..dc6b2aecb5 100644
--- a/ci/test/00_setup_env_native_qt5.sh
+++ b/ci/test/00_setup_env_native_qt5.sh
@@ -7,7 +7,7 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_native_qt5
-export DOCKER_NAME_TAG=ubuntu:18.04  # Check that bionic can compile our c++17 and run our functional tests in python3
+export DOCKER_NAME_TAG=ubuntu:18.04  # Check that bionic gcc-7 can compile our c++17 and run our functional tests in python3, see doc/dependencies.md
 export PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools libdbus-1-dev libharfbuzz-dev"
 export DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1"
 export TEST_RUNNER_EXTRA="--previous-releases --coverage --extended --exclude feature_dbcrash"  # Run extended tests so that coverage does not fail, but exclude the very slow dbcrash
@@ -16,4 +16,4 @@ export RUN_UNIT_TESTS_SEQUENTIAL="true"
 export RUN_UNIT_TESTS="false"
 export GOAL="install"
 export PREVIOUS_RELEASES_TO_DOWNLOAD="v0.15.2 v0.16.3 v0.17.2 v0.18.1 v0.19.1"
-export BITCOIN_CONFIG="--enable-zmq --with-libs=no --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports --enable-c++17 --enable-debug CFLAGS=\"-g0 -O2 -funsigned-char\" CXXFLAGS=\"-g0 -O2 -funsigned-char\" --with-boost-process"
+export BITCOIN_CONFIG="--enable-zmq --with-libs=no --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports --enable-debug CFLAGS=\"-g0 -O2 -funsigned-char\" CXXFLAGS=\"-g0 -O2 -funsigned-char\" --with-boost-process"
diff --git a/ci/test/04_install.sh b/ci/test/04_install.sh
index db74fe6569..cce0c7e49e 100755
--- a/ci/test/04_install.sh
+++ b/ci/test/04_install.sh
@@ -60,8 +60,8 @@ if [ -n "$DPKG_ADD_ARCH" ]; then
 fi
 
 if [[ $DOCKER_NAME_TAG == centos* ]]; then
-  ${CI_RETRY_EXE} DOCKER_EXEC yum -y install epel-release
-  ${CI_RETRY_EXE} DOCKER_EXEC yum -y install $DOCKER_PACKAGES $PACKAGES
+  ${CI_RETRY_EXE} DOCKER_EXEC dnf -y install epel-release
+  ${CI_RETRY_EXE} DOCKER_EXEC dnf -y --allowerasing install $DOCKER_PACKAGES $PACKAGES
 elif [ "$CI_USE_APT_INSTALL" != "no" ]; then
   ${CI_RETRY_EXE} DOCKER_EXEC apt-get update
   ${CI_RETRY_EXE} DOCKER_EXEC apt-get install --no-install-recommends --no-upgrade -y $PACKAGES $DOCKER_PACKAGES
diff --git a/configure.ac b/configure.ac
index 01041ceab1..e1548e5c36 100644
--- a/configure.ac
+++ b/configure.ac
@@ -68,18 +68,8 @@ case $host in
   ;;
 esac
 
-AC_ARG_ENABLE([c++17],
-  [AS_HELP_STRING([--enable-c++17],
-  [enable compilation in c++17 mode (disabled by default)])],
-  [use_cxx17=$enableval],
-  [use_cxx17=no])
-
-dnl Require C++11 or C++17 compiler (no GNU extensions)
-if test "x$use_cxx17" = xyes -o "x$enable_fuzz" = xyes ; then
-  AX_CXX_COMPILE_STDCXX([17], [noext], [mandatory])
-else
-  AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory])
-fi
+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/doc/dependencies.md b/doc/dependencies.md
index 08fbf6145d..6a743caba2 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/) | [1.58.0](https://github.com/bitcoin/bitcoin/pull/19667) | 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 |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) (Android only) |
-| GCC |  | [4.8+](https://gcc.gnu.org/) (C++11 support) |  |  |  |
+| GCC |  | [7+](https://gcc.gnu.org/) (C++17 support) |  |  |  |
 | HarfBuzz-NG |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) |
 | libevent | [2.1.11-stable](https://github.com/libevent/libevent/releases) | [2.0.21](https://github.com/bitcoin/bitcoin/pull/18676) | No |  |  |
 | libpng |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) |
diff --git a/src/util/memory.h b/src/util/memory.h
index 15ecf8f80d..4d73b32869 100644
--- a/src/util/memory.h
+++ b/src/util/memory.h
@@ -10,10 +10,11 @@
 #include <utility>
 
 //! Substitute for C++14 std::make_unique.
+//! DEPRECATED use std::make_unique in new code.
 template <typename T, typename... Args>
 std::unique_ptr<T> MakeUnique(Args&&... args)
 {
-    return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+    return std::make_unique<T>(std::forward<Args>(args)...);
 }
 
 #endif