From db7e6996294cc66d3f9d132267fbc64dd7b97acb Mon Sep 17 00:00:00 2001
From: Alexey Pavlov <alexpux@gmail.com>
Date: Fri, 5 Sep 2025 15:15:15 +0300
Subject: [PATCH 003/N] sysmodule: Implement flags "_is_mingw",
 "is_mingw_ucrt" and "_use_alt_sep"

---
 Python/sysmodule.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 993763f..e722a59 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -177,6 +177,38 @@ PySys_GetObject(const char *name)
     return value;
 }
 
+static int
+use_alt_sep(void)
+{
+#ifdef MS_WINDOWS
+    char* msystem = getenv("MSYSTEM");
+    if (msystem != NULL && strcmp(msystem, "") != 0) {
+        return 1;
+    }
+#endif
+    return 0;
+}
+
+static int
+is_mingw(void)
+{
+#ifdef __MINGW32__
+    return 1;
+#else
+    return 0;
+#endif
+}
+
+static int
+is_mingw_ucrt(void)
+{
+#if defined(__MINGW32__) && defined(_UCRT)
+    return 1;
+#else
+    return 0;
+#endif
+}
+
 static int
 sys_set_object(PyInterpreterState *interp, PyObject *key, PyObject *v)
 {
@@ -3622,6 +3654,10 @@ _PySys_InitCore(PyThreadState *tstate, PyObject *sysdict)
     SET_SYS_FROM_STRING("byteorder", "little");
 #endif
 
+    SET_SYS("_is_mingw", PyLong_FromLong(is_mingw()));
+    SET_SYS("_is_mingw_ucrt", PyLong_FromLong(is_mingw_ucrt()));
+    SET_SYS("_use_alt_sep", PyLong_FromLong(use_alt_sep()));
+
 #ifdef MS_COREDLL
     SET_SYS("dllhandle", PyLong_FromVoidPtr(PyWin_DLLhModule));
     SET_SYS_FROM_STRING("winver", PyWin_DLLVersionString);