Improve Windows compatibility and CMake flags

Moved <stdatomic.h> include and atomic variables to non-Windows platforms in vsort.c, and added Windows-specific initialization using InitOnce. Updated CMakeLists.txt to set compiler flags conditionally for MSVC, enforce C17 standard, and avoid non-portable flags on Windows.

Author: davidesantangelo

CMakeLists.txt

@@ -38,8 +38,11 @@ check_ipo_supported(RESULT ipo_supported OUTPUT ipo_error)
 if(ipo_supported)
     set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
 endif()
-set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -Ofast -march=native -fomit-frame-pointer -flto -ffast-math")
-set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto")
+
+if(NOT MSVC)
+    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -Ofast -march=native -fomit-frame-pointer -flto -ffast-math")
+    set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto")
+endif()
 
 # Add logger source files
 set(VSORT_SOURCES vsort.c vsort_logger.c)
@@ -100,10 +103,10 @@ endif()
 if(MSVC)
     # MSVC (Visual Studio) compiler flags
     target_compile_options(vsort PRIVATE 
+        /std:c17        # Enable C17 mode for proper headers
         /O2             # Optimize for speed
         /Ob2            # Inline function expansion
         /Oi             # Enable intrinsic functions
-        /Ot             # Favor fast code
         /Gy             # Function-level linking
         /fp:fast        # Fast floating point model
     )
@@ -161,6 +164,7 @@ foreach(example ${EXAMPLES})
     # Add Windows-specific configurations for examples
     if(MSVC)
         target_compile_options(${example} PRIVATE 
+            /std:c17        # Match library C standard
             /O2             # Optimize for speed
             /fp:fast        # Fast floating point model
         )
@@ -187,6 +191,7 @@ foreach(test ${TESTS})
     # Add Windows-specific configurations for tests
     if(MSVC)
         target_compile_options(${test} PRIVATE 
+            /std:c17        # Match library C standard
             /O2             # Optimize for speed
             /fp:fast        # Fast floating point model
         )

vsort.c

@@ -21,7 +21,6 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
-#include <stdatomic.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -36,6 +35,7 @@
 #if defined(_WIN32) || defined(_MSC_VER)
 #include <windows.h>
 #else
+#include <stdatomic.h>
 #include <sched.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ -119,8 +119,12 @@ static vsort_runtime_t g_runtime = {
     .log_level = VSORT_LOG_WARNING,
     .logger_ready = false};
 
+#if defined(_WIN32) || defined(_MSC_VER)
+static INIT_ONCE g_runtime_once = INIT_ONCE_STATIC_INIT;
+#else
 static atomic_bool g_runtime_init_requested = ATOMIC_VAR_INIT(false);
 static atomic_bool g_runtime_ready = ATOMIC_VAR_INIT(false);
+#endif
 
 static vsort_runtime_t *vsort_runtime(void);
 static void vsort_runtime_initialize(void);
@@ -438,9 +442,26 @@ static void vsort_runtime_initialize(void)
                     rt->thresholds.radix_threshold,
                     rt->thresholds.cache_optimal_elements);
 
+#if !defined(_WIN32) && !defined(_MSC_VER)
     atomic_store(&g_runtime_ready, true);
+#endif
 }
 
+#if defined(_WIN32) || defined(_MSC_VER)
+static BOOL CALLBACK vsort_runtime_once_callback(PINIT_ONCE once, PVOID param, PVOID *context)
+{
+    VSORT_UNUSED(once);
+    VSORT_UNUSED(param);
+    VSORT_UNUSED(context);
+    vsort_runtime_initialize();
+    return TRUE;
+}
+
+VSORT_API void vsort_init(void)
+{
+    InitOnceExecuteOnce(&g_runtime_once, vsort_runtime_once_callback, NULL, NULL);
+}
+#else
 VSORT_API void vsort_init(void)
 {
     bool expected = false;
@@ -452,14 +473,11 @@ VSORT_API void vsort_init(void)
     {
         while (!atomic_load(&g_runtime_ready))
         {
-#if defined(_WIN32) || defined(_MSC_VER)
-            Sleep(0);
-#else
             sched_yield();
-#endif
         }
     }
 }
+#endif
 
 // -----------------------------------------------------------------------------
 // Memory helpers