CMAKE_CXX_STANDARD: 17 -> 20

This allows us to use heterogenous `unordered_map` where available.

.github/workflows/Android.yml

@@ -35,8 +35,8 @@ jobs:
       uses: actions/cache@v2
       with:
         path: android-project/app/.cxx
-        key: android-cmake-v2-${{ github.sha }}
+        key: android-cmake-v3-${{ github.sha }}
-        restore-keys: android-cmake-v2-
+        restore-keys: android-cmake-v3-
 
     - name: Build
       working-directory: ${{github.workspace}}

.github/workflows/Linux_x86.yml

@@ -26,8 +26,8 @@ jobs:
       uses: actions/cache@v2
       with:
         path: build
-        key: linux-x86-cmake-v4-${{ github.sha }}
+        key: linux-x86-cmake-v5-${{ github.sha }}
-        restore-keys: linux-x86-cmake-v4-
+        restore-keys: linux-x86-cmake-v5-
 
     - name: Configure CMake
       shell: bash

.github/workflows/Linux_x86_64_SDL1.yml

@@ -25,8 +25,8 @@ jobs:
       uses: actions/cache@v2
       with:
         path: build
-        key: linux-x86_64-sdl1-cmake-v3-${{ github.sha }}
+        key: linux-x86_64-sdl1-cmake-v4-${{ github.sha }}
-        restore-keys: linux-x86_64-sdl1-cmake-v3-
+        restore-keys: linux-x86_64-sdl1-cmake-v4-
 
     - name: Configure CMake
       shell: bash

.github/workflows/Linux_x86_64_test.yml

@@ -26,8 +26,8 @@ jobs:
         uses: actions/cache@v3
         with:
           path: build
-          key: linux-x86-64-test-cmake-v1-${{ github.sha }}
+          key: linux-x86-64-test-cmake-v2-${{ github.sha }}
-          restore-keys: linux-x86-64-test-cmake-v1-
+          restore-keys: linux-x86-64-test-cmake-v2-
       - name: Build tests
         run: |
           cmake -S. -Bbuild -DENABLE_CODECOVERAGE=ON

.github/workflows/MacOSX.yml

@@ -31,8 +31,8 @@ jobs:
       uses: actions/cache@v2
       with:
         path: build
-        key: macos-cmake-v2-${{ github.sha }}
+        key: macos-cmake-v3-${{ github.sha }}
-        restore-keys: macos-cmake-v2-
+        restore-keys: macos-cmake-v3-
 
     - name: Configure CMake
       # Use a bash shell so we can use the same syntax for environment variable

.github/workflows/iOS.yml

@@ -24,8 +24,8 @@ jobs:
       uses: actions/cache@v2
       with:
         path: build
-        key: ios-cmake-v2-${{ github.sha }}
+        key: ios-cmake-v3-${{ github.sha }}
-        restore-keys: ios-cmake-v2-
+        restore-keys: ios-cmake-v3-
 
     - name: Configure CMake
       # Use a bash shell so we can use the same syntax for environment variable

CMakeLists.txt

@@ -205,9 +205,9 @@ if(GPERF)
   endif()
 endif()
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD_REQUIRED OFF)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON) # for clang-tidy
 set(CMAKE_THREAD_PREFER_PTHREAD ON)
 set(THREADS_PREFER_PTHREAD_FLAG ON)