Require c++17 at mimumum

.github/workflows/ci.yml

@@ -12,10 +12,13 @@ jobs:
       fail-fast: false
       matrix:
         config:
+          - { compiler: gcc, version: 11, build_type: Debug, cppstd: 17 }
           - { compiler: gcc, version: 11, build_type: Debug, cppstd: 20 }
+          - { compiler: gcc, version: 13, build_type: Release, cppstd: 17 }
           - { compiler: gcc, version: 13, build_type: Release, cppstd: 20 }
           - { compiler: gcc, version: 13, build_type: Release, cppstd: 20, std_format: OFF }
           - { compiler: gcc, version: 13, build_type: Release, cppstd: 20, std_format: ON }
+          - { compiler: clang, version: 15, build_type: Release, cppstd: 17}
           - { compiler: clang, version: 15, build_type: Debug, cppstd: 20, asan: ON }
           - { compiler: clang, version: 15, build_type: Release, cppstd: 20, asan: OFF }
     container:

CMakeLists.txt

@@ -25,7 +25,13 @@ endif()
 # ---------------------------------------------------------------------------------------
 # Compiler config
 # ---------------------------------------------------------------------------------------
-set(CMAKE_CXX_STANDARD 20)
+
+# c++ standard >=17 is required
+if(NOT DEFINED CMAKE_CXX_STANDARD)
+    set(CMAKE_CXX_STANDARD 17)
+elseif(CMAKE_CXX_STANDARD LESS 17)
+        message(FATAL_ERROR "Minimum supported CMAKE_CXX_STANDARD is 17, but CMAKE_CXX_STANDARD is set to a lower value.")
+endif()
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # make sure __cplusplus is defined when using msvc and enable parallel build

appveyor.yml

@@ -9,7 +9,7 @@ environment:
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
       USE_STD_FORMAT: 'OFF'
-      CXX_STANDARD: 11
+      CXX_STANDARD: 17
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'OFF'
@@ -17,7 +17,7 @@ environment:
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
       USE_STD_FORMAT: 'OFF'
-      CXX_STANDARD: 11
+      CXX_STANDARD: 17
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'
@@ -25,7 +25,7 @@ environment:
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
       USE_STD_FORMAT: 'OFF'
-      CXX_STANDARD: 11
+      CXX_STANDARD: 17
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'
@@ -33,7 +33,7 @@ environment:
       WCHAR_FILES: 'ON'
       BUILD_EXAMPLE: 'OFF'
       USE_STD_FORMAT: 'OFF'
-      CXX_STANDARD: 11
+      CXX_STANDARD: 17
     - GENERATOR: '"Visual Studio 16 2019" -A x64'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'