build: Require C++20 compiler

Author: MarcoFalke

.github/workflows/ci.yml

@@ -62,12 +62,12 @@ jobs:
           echo "TEST_BASE=$(git rev-list -n$((${{ env.MAX_COUNT }} + 1)) --reverse HEAD ^$(git rev-list -n1 --merges HEAD)^@ | head -1)" >> "$GITHUB_ENV"
       - run: |
           sudo apt-get update
-          sudo apt-get install clang ccache build-essential libtool autotools-dev automake pkg-config bsdmainutils python3-zmq libevent-dev libboost-dev libsqlite3-dev libdb++-dev systemtap-sdt-dev libminiupnpc-dev libnatpmp-dev libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools qtwayland5 libqrencode-dev -y
+          sudo apt-get install clang-15 ccache build-essential libtool autotools-dev automake pkg-config bsdmainutils python3-zmq libevent-dev libboost-dev libsqlite3-dev libdb++-dev systemtap-sdt-dev libminiupnpc-dev libnatpmp-dev libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools qtwayland5 libqrencode-dev -y
       - name: Compile and run tests
         run: |
           # Run tests on commits after the last merge commit and before the PR head commit
           # Use clang++, because it is a bit faster and uses less memory than g++
-          git rebase --exec "echo Running test-one-commit on \$( git log -1 ) && ./autogen.sh && CC=clang CXX=clang++ ./configure && make clean && make -j $(nproc) check && ./test/functional/test_runner.py -j $(( $(nproc) * 2 ))" ${{ env.TEST_BASE }}
+          git rebase --exec "echo Running test-one-commit on \$( git log -1 ) && ./autogen.sh && CC=clang-15 CXX=clang++-15 ./configure && make clean && make -j $(nproc) check && ./test/functional/test_runner.py -j $(( $(nproc) * 2 ))" ${{ env.TEST_BASE }}
 
   macos-native-x86_64:
     name: 'macOS 13 native, x86_64, no depends, sqlite only, gui'

build-aux/m4/ax_cxx_compile_stdcxx.m4

@@ -983,7 +983,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_20], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 202002L
+#elif __cplusplus < 201709L  // Temporary patch on top of upstream to allow g++-10
 
 #error "This is not a C++20 compiler"
 

configure.ac

@@ -96,18 +96,8 @@ case $host in
   ;;
 esac
 
-AC_ARG_ENABLE([c++20],
-  [AS_HELP_STRING([--enable-c++20],
-  [enable compilation in c++20 mode (disabled by default)])],
-  [use_cxx20=$enableval],
-  [use_cxx20=no])
-
-dnl Require C++17 compiler (no GNU extensions)
-if test "$use_cxx20" = "no"; then
-AX_CXX_COMPILE_STDCXX([17], [noext], [mandatory])
-else
+dnl Require C++20 compiler (no GNU extensions)
 AX_CXX_COMPILE_STDCXX([20], [noext], [mandatory])
-fi
 
 dnl Unless the user specified OBJCXX, force it to be the same as CXX. This ensures
 dnl that we get the same -std flags for both.

depends/Makefile

@@ -49,7 +49,7 @@ NO_HARDEN ?=
 FALLBACK_DOWNLOAD_PATH ?= https://bitcoincore.org/depends-sources
 
 C_STANDARD ?= c11
-CXX_STANDARD ?= c++17
+CXX_STANDARD ?= c++20
 
 BUILD = $(shell ./config.guess)
 HOST ?= $(BUILD)

depends/README.md

@@ -98,7 +98,7 @@ The following can be set when running make: `make FOO=bar`
 - `SDK_PATH`: Path where SDKs can be found (used by macOS)
 - `FALLBACK_DOWNLOAD_PATH`: If a source file can't be fetched, try here before giving up
 - `C_STANDARD`: Set the C standard version used. Defaults to `c11`.
-- `CXX_STANDARD`: Set the C++ standard version used. Defaults to `c++17`.
+- `CXX_STANDARD`: Set the C++ standard version used. Defaults to `c++20`.
 - `NO_BOOST`: Don't download/build/cache Boost
 - `NO_LIBEVENT`: Don't download/build/cache Libevent
 - `NO_QT`: Don't download/build/cache Qt and its dependencies

depends/packages/qt.mk

@@ -41,7 +41,7 @@ $(package)_config_opts_release += -silent
 $(package)_config_opts_debug = -debug
 $(package)_config_opts_debug += -optimized-tools
 $(package)_config_opts += -bindir $(build_prefix)/bin
-$(package)_config_opts += -c++std c++17
+$(package)_config_opts += -c++std c++2a
 $(package)_config_opts += -confirm-license
 $(package)_config_opts += -hostprefix $(build_prefix)
 $(package)_config_opts += -no-compile-examples

src/.clang-format

@@ -43,5 +43,5 @@ SpacesInAngles:  false
 SpacesInContainerLiterals: true
 SpacesInCStyleCastParentheses: false
 SpacesInParentheses: false
-Standard:        c++17
+Standard: c++20
 UseTab:          Never