From da33d606e6f6563e8006ebac06e22194f1f27014 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 23 Apr 2026 15:47:58 -0400
Subject: [PATCH] PellesC: Add support for C language standards

Issue: #21536
Inspired-by: Serguei E. Leontiev <leo@sai.msu.ru>
---
 .../ci/configure_windows_pellesc_common.cmake  |  2 ++
 Modules/CMakeCCompilerId.c.in                  |  2 ++
 Modules/Compiler/PellesC-C.cmake               | 18 ++++++++++++++++++
 Tests/CMakeLists.txt                           |  1 +
 Tests/CompileFeatures/c_std.h                  |  2 ++
 5 files changed, 25 insertions(+)

diff --git a/.gitlab/ci/configure_windows_pellesc_common.cmake b/.gitlab/ci/configure_windows_pellesc_common.cmake
index bc2cc5173a..7027e7c617 100644
--- a/.gitlab/ci/configure_windows_pellesc_common.cmake
+++ b/.gitlab/ci/configure_windows_pellesc_common.cmake
@@ -1,6 +1,8 @@
 set(CMake_TEST_CXX OFF CACHE BOOL "")
 set(CMake_TEST_Java OFF CACHE BOOL "")
 
+set(CMake_TEST_C_STANDARDS "90;99;11;17;23" CACHE STRING "")
+
 set(configure_no_sccache 1)
 
 include("${CMAKE_CURRENT_LIST_DIR}/configure_external_test.cmake")
diff --git a/Modules/CMakeCCompilerId.c.in b/Modules/CMakeCCompilerId.c.in
index 65d3bab50d..165376ddba 100644
--- a/Modules/CMakeCCompilerId.c.in
+++ b/Modules/CMakeCCompilerId.c.in
@@ -74,6 +74,8 @@ const char* info_language_extensions_default = "INFO" ":" "extensions_default["
      defined(__TI_COMPILER_VERSION__) || defined(__RENESAS__)) &&             \
   !defined(__STRICT_ANSI__)
   "ON"
+#elif defined(__POCC__) && defined(__POCC__EXTENSIONS)
+  "ON"
 #else
   "OFF"
 #endif
diff --git a/Modules/Compiler/PellesC-C.cmake b/Modules/Compiler/PellesC-C.cmake
index c97fa64ced..4381e127e3 100644
--- a/Modules/Compiler/PellesC-C.cmake
+++ b/Modules/Compiler/PellesC-C.cmake
@@ -6,3 +6,21 @@ __compiler_pellesc(C)
 
 set(CMAKE_C_OUTPUT_EXTENSION ".obj")
 set(CMAKE_C_VERBOSE_FLAG "-V2")
+
+include (Compiler/CMakeCommonCompilerMacros)
+
+set(CMAKE_C90_STANDARD_COMPILE_OPTION "") # No C90-only mode.
+set(CMAKE_C90_STANDARD__HAS_FULL_SUPPORT ON)
+set(CMAKE_C99_STANDARD_COMPILE_OPTION -std=c99)
+set(CMAKE_C99_EXTENSION_COMPILE_OPTION -std=c99 -Zx)
+set(CMAKE_C99_STANDARD__HAS_FULL_SUPPORT ON)
+set(CMAKE_C11_STANDARD_COMPILE_OPTION -std=c11)
+set(CMAKE_C11_EXTENSION_COMPILE_OPTION -std=c11 -Zx)
+set(CMAKE_C11_STANDARD__HAS_FULL_SUPPORT ON)
+set(CMAKE_C17_STANDARD_COMPILE_OPTION -std=c17)
+set(CMAKE_C17_EXTENSION_COMPILE_OPTION -std=c17 -Zx)
+set(CMAKE_C23_STANDARD_COMPILE_OPTION -std=c23)
+set(CMAKE_C23_EXTENSION_COMPILE_OPTION -std=c23 -Zx)
+set(CMAKE_C_STANDARD_LATEST 23)
+
+__compiler_check_default_language_standard(C 12.0 23)
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index 7a70421256..210363e5a5 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -440,6 +440,7 @@ if(BUILD_TESTING)
     )
   ADD_TEST_MACRO(CompileFeatures CompileFeatures)
   set_property(TEST CompileFeatures APPEND PROPERTY LABELS "CUDA" "HIP")
+  set_property(TEST CompileFeatures APPEND PROPERTY LABELS "PellesC")
 
   ADD_TEST_MACRO(CMakeCommands.target_compile_features)
 
diff --git a/Tests/CompileFeatures/c_std.h b/Tests/CompileFeatures/c_std.h
index afe0308882..7e6402d49f 100644
--- a/Tests/CompileFeatures/c_std.h
+++ b/Tests/CompileFeatures/c_std.h
@@ -5,4 +5,6 @@
 
 #ifdef __STDC_VERSION__
 #  define C_STD __STDC_VERSION__
+#elif defined(__POCC_STDC_VERSION__)
+#  define C_STD __POCC_STDC_VERSION__
 #endif