From 78005695a1b186234477f7ca34ad75770394f05b Mon Sep 17 00:00:00 2001
From: Alexander Vieth <vieth.alexander@gmx.net>
Date: Thu, 11 Sep 2025 12:27:49 +0200
Subject: [PATCH] Allow C17 for newer CMake versions (#1958)

---
 .github/workflows/cmake.yml | 31 +++++++++++++++++++++++++++++++
 CMakeLists.txt              |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index a5bf8f2d..5408f897 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -86,6 +86,18 @@ jobs:
             packages: gcc-multilib g++-multilib
             codecov: ubuntu_gcc_m32
 
+          - name: Ubuntu GCC C17
+            os: ubuntu-latest
+            compiler: gcc
+            cxx-compiler: g++
+            cmake-args: -DCMAKE_C_STANDARD=17
+
+          - name: Ubuntu GCC C23
+            os: ubuntu-latest
+            compiler: gcc
+            cxx-compiler: g++
+            cmake-args: -DCMAKE_C_STANDARD=23
+
           - name: Ubuntu GCC No Chorba
             os: ubuntu-latest
             compiler: gcc
@@ -422,6 +434,20 @@ jobs:
             gcov-exec: llvm-cov-15 gcov
             codecov: ubuntu_clang
 
+          - name: Ubuntu Clang C17
+            os: ubuntu-latest
+            compiler: clang-15
+            cxx-compiler: clang++-15
+            cmake-args: -DCMAKE_C_STANDARD=17
+            packages: clang-15 llvm-15 llvm-15-tools
+
+          - name: Ubuntu Clang C23
+            os: ubuntu-latest
+            compiler: clang-18
+            cxx-compiler: clang++-18
+            cmake-args: -DCMAKE_C_STANDARD=23
+            packages: clang-18 llvm-18 llvm-18-tools
+
           # Check for undefined symbols in the version script for the modern api
           - name: Ubuntu Clang Undefined Symbols
             os: ubuntu-latest
@@ -515,6 +541,11 @@ jobs:
             compiler: cl
             cmake-args: -G "Visual Studio 17 2022" -A x64 -T v143 -DWITH_NATIVE_INSTRUCTIONS=ON -DNATIVE_ARCH_OVERRIDE=/arch:AVX
 
+          - name: Windows MSVC 2022 v143 Win64 C17
+            os: windows-latest
+            compiler: cl
+            cmake-args: -G "Visual Studio 17 2022" -A x64 -T v143 -DCMAKE_C_STANDARD=17
+
           - name: Windows MSVC 2022 v142 Win32
             os: windows-latest
             compiler: cl
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 38885089..f2d03979 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,6 +21,9 @@ if(NOT DEFINED CMAKE_C_EXTENSIONS)
     set(CMAKE_C_EXTENSIONS OFF)       # Boolean specifying whether compiler specific extensions are requested
 endif()
 set(VALID_C_STANDARDS "99" "11")
+if(CMAKE_VERSION VERSION_GREATER 3.20)
+    list(APPEND VALID_C_STANDARDS "17" "23")
+endif()
 if(NOT CMAKE_C_STANDARD IN_LIST VALID_C_STANDARDS)
     MESSAGE(FATAL_ERROR "CMAKE_C_STANDARD:STRING=${CMAKE_C_STANDARD} not in known standards list\n ${VALID_C_STANDARDS}")
 endif()
-- 
2.47.3