Check for required C++ features during initial build (std::format, etc)

.github/workflows/symbols-check.yml

@@ -13,7 +13,7 @@ concurrency:
 
 jobs:
   Run:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
 
     timeout-minutes: 10
     steps:

CMakeLists.txt

@@ -62,6 +62,17 @@ set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+include (cmake/CheckCXXFeature.cmake)
+include (cmake/RequireCXXFeature.cmake)
+# Reference: https://en.cppreference.com/w/cpp/utility/feature_test
+
+# Required C++ features
+require_cxx_feature(__cpp_constexpr)
+
+# Required C++ standard library features
+require_cxx_feature(__cpp_lib_format)
+
+
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pthread -g -Wall -pedantic -Wextra -fPIC")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread -g -Wall -fno-strict-aliasing -pedantic -Wnon-virtual-dtor -Wextra -fPIC")
 set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--as-needed")

cmake/CheckCXXFeature.cmake

@@ -0,0 +1,24 @@
+
+# https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations#table-of-feature-test-macros
+# https://en.cppreference.com/w/cpp/feature_test
+# https://en.cppreference.com/w/cpp/utility/feature_test
+
+include_guard(GLOBAL)
+
+#include (CheckSymbolExists)
+include (CheckCXXSymbolExists)
+
+macro(CHECK_CXX_FEATURE SYMBOL VARIABLE)
+  if (NOT DEFINED "${SYMBOL}")
+    # Feature testing is only available since C++20
+    if (NOT CMAKE_CXX_COMPILE_FEATURES MATCHES "cxx_std_20")
+      message(FATAL_ERROR "C++20 support is required!\n")
+    endif()
+
+    # Header containing the available C++ standard library features
+    set(FILES "version")
+
+    #__CHECK_SYMBOL_EXISTS_IMPL(RequireCXXFeature.cxx "${SYMBOL}" "${FILES}" "${VARIABLE}")
+    check_cxx_symbol_exists("${SYMBOL}" "${FILES}" "${VARIABLE}")
+  endif()
+endmacro()

cmake/RequireCXXFeature.cmake

@@ -0,0 +1,31 @@
+
+# https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations#table-of-feature-test-macros
+# https://en.cppreference.com/w/cpp/feature_test
+# https://en.cppreference.com/w/cpp/utility/feature_test
+
+include_guard(GLOBAL)
+
+#include (CheckSymbolExists)
+include (CheckCXXSymbolExists)
+
+macro(REQUIRE_CXX_FEATURE SYMBOL)
+  if (NOT DEFINED "${SYMBOL}")
+    # Feature testing is only available since C++20
+    if (NOT CMAKE_CXX_COMPILE_FEATURES MATCHES "cxx_std_20")
+      message(FATAL_ERROR "C++20 support is required!\n")
+    endif()
+
+    # Header containing the available C++ standard library features
+    set(FILES "version")
+
+    #__CHECK_SYMBOL_EXISTS_IMPL(RequireCXXFeature.cxx "${SYMBOL}" "${FILES}" "${SYMBOL}")
+    check_cxx_symbol_exists("${SYMBOL}" "${FILES}" "${SYMBOL}")
+
+    # To us, failure is a fatal error
+    if (NOT "${${SYMBOL}}")
+      # Unset the variable cached by "symbol exists" check
+      unset("${SYMBOL}" CACHE)
+      message(FATAL_ERROR "Required C++ feature ${SYMBOL} not found!\nSee the feature test documentation, or https://en.cppreference.com/w/cpp/feature_test for details.\n")
+    endif()
+  endif()
+endmacro()

doc/sphinx/.readthedocs.yaml

@@ -7,7 +7,7 @@ version: 2
 
 # Set the version of Python and other tools you might need
 build:
-  os: ubuntu-22.04
+  os: ubuntu-24.04
   tools:
     python: "3.11"
   # https://github.com/readthedocs/readthedocs.org/issues/9599