diff --git a/reactos/include/crt/sec_api/string_s.h b/reactos/include/crt/sec_api/string_s.h
index 24d60320bb7..0516c0be498 100644
--- a/reactos/include/crt/sec_api/string_s.h
+++ b/reactos/include/crt/sec_api/string_s.h
@@ -3,6 +3,7 @@
  * This file is part of the w64 mingw-runtime package.
  * No warranty is given; refer to the file DISCLAIMER within this package.
  */
+
 #ifndef _INC_STRING_S
 #define _INC_STRING_S
 
@@ -14,46 +15,299 @@
 extern "C" {
 #endif
 
-  _CRTIMP errno_t __cdecl _strset_s(char *_Dst,size_t _DstSize,int _Value);
-  _CRTIMP errno_t __cdecl _strerror_s(char *_Buf,size_t _SizeInBytes,const char *_ErrMsg);
-  _CRTIMP errno_t __cdecl _strlwr_s(char *_Str,size_t _Size);
-  _CRTIMP errno_t __cdecl _strlwr_s_l(char *_Str,size_t _Size,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl _strnset_s(char *_Str,size_t _Size,int _Val,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _strupr_s(char *_Str,size_t _Size);
-  _CRTIMP errno_t __cdecl _strupr_s_l(char *_Str,size_t _Size,_locale_t _Locale);
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strset_s(
+    _Inout_updates_z_(_DstSize) char *_Dst,
+    _In_ size_t _DstSize,
+    _In_ int _Value);
 
-  _CRTIMP errno_t __cdecl strncat_s(char *_Dst,size_t _DstSizeInChars,const char *_Src,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _strncat_s_l(char *_Dst,size_t _DstSizeInChars,const char *_Src,size_t _MaxCount,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl strcpy_s(char *_Dst, size_t _SizeInBytes, const char *_Src);
-  _CRTIMP errno_t __cdecl strncpy_s(char *_Dst,size_t _DstSizeInChars,const char *_Src,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _strncpy_s_l(char *_Dst,size_t _DstSizeInChars,const char *_Src,size_t _MaxCount,_locale_t _Locale);
-  _CRTIMP char *__cdecl strtok_s(char *_Str,const char *_Delim,char **_Context);
-  _CRTIMP char *__cdecl _strtok_s_l(char *_Str,const char *_Delim,char **_Context,_locale_t _Locale);
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strerror_s(
+    _Out_writes_z_(_SizeInBytes) char *_Buf,
+    _In_ size_t _SizeInBytes,
+    _In_opt_z_ const char *_ErrMsg);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strlwr_s(
+    _Inout_updates_z_(_Size) char *_Str,
+    _In_ size_t _Size);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strlwr_s_l(
+    _Inout_updates_z_(_Size) char *_Str,
+    _In_ size_t _Size,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strnset_s(
+    _Inout_updates_z_(_Size) char *_Str,
+    _In_ size_t _Size,
+    _In_ int _Val,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strupr_s(
+    _Inout_updates_z_(_Size) char *_Str,
+    _In_ size_t _Size);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strupr_s_l(
+    _Inout_updates_z_(_Size) char *_Str,
+    _In_ size_t _Size,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  strncat_s(
+    _Inout_updates_z_(_DstSizeInChars) char *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const char *_Src,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strncat_s_l(
+    _Inout_updates_z_(_DstSizeInChars) char *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const char *_Src,
+    _In_ size_t _MaxCount,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  strcpy_s(
+    _Out_writes_z_(_SizeInBytes) char *_Dst,
+    _In_ size_t _SizeInBytes,
+    _In_z_ const char *_Src);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  strncpy_s(
+    _Out_writes_z_(_DstSizeInChars) char *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const char *_Src,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _strncpy_s_l(
+    _Out_writes_z_(_DstSizeInChars) char *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const char *_Src,
+    _In_ size_t _MaxCount,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_
+  _CRTIMP
+  char *
+  __cdecl
+  strtok_s(
+    _Inout_opt_z_ char *_Str,
+    _In_z_ const char *_Delim,
+    _Inout_ _Deref_prepost_opt_z_ char **_Context);
+
+  _Check_return_
+  _CRTIMP
+  char *
+  __cdecl
+  _strtok_s_l(
+    _Inout_opt_z_ char *_Str,
+    _In_z_ const char *_Delim,
+    _Inout_ _Deref_prepost_opt_z_ char **_Context,
+    _In_opt_ _locale_t _Locale);
 
 #ifndef _WSTRING_S_DEFINED
 #define _WSTRING_S_DEFINED
-  _CRTIMP wchar_t *__cdecl wcstok_s(wchar_t *_Str,const wchar_t *_Delim,wchar_t **_Context);
-  _CRTIMP errno_t __cdecl _wcserror_s(wchar_t *_Buf,size_t _SizeInWords,int _ErrNum);
-  _CRTIMP errno_t __cdecl __wcserror_s(wchar_t *_Buffer,size_t _SizeInWords,const wchar_t *_ErrMsg);
-  _CRTIMP errno_t __cdecl _wcsnset_s(wchar_t *_Dst,size_t _DstSizeInWords,wchar_t _Val,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _wcsset_s(wchar_t *_Str,size_t _SizeInWords,wchar_t _Val);
-  _CRTIMP errno_t __cdecl _wcslwr_s(wchar_t *_Str,size_t _SizeInWords);
-  _CRTIMP errno_t __cdecl _wcslwr_s_l(wchar_t *_Str,size_t _SizeInWords,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl _wcsupr_s(wchar_t *_Str,size_t _Size);
-  _CRTIMP errno_t __cdecl _wcsupr_s_l(wchar_t *_Str,size_t _Size,_locale_t _Locale);
 
-  _CRTIMP errno_t __cdecl wcsncat_s(wchar_t *_Dst,size_t _DstSizeInChars,const wchar_t *_Src,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _wcsncat_s_l(wchar_t *_Dst,size_t _DstSizeInChars,const wchar_t *_Src,size_t _MaxCount,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl wcsncpy_s(wchar_t *_Dst,size_t _DstSizeInChars,const wchar_t *_Src,size_t _MaxCount);
-  _CRTIMP errno_t __cdecl _wcsncpy_s_l(wchar_t *_Dst,size_t _DstSizeInChars,const wchar_t *_Src,size_t _MaxCount,_locale_t _Locale);
-  _CRTIMP wchar_t *__cdecl _wcstok_s_l(wchar_t *_Str,const wchar_t *_Delim,wchar_t **_Context,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl _wcsset_s_l(wchar_t *_Str,size_t _SizeInChars,unsigned int _Val,_locale_t _Locale);
-  _CRTIMP errno_t __cdecl _wcsnset_s_l(wchar_t *_Str,size_t _SizeInChars,unsigned int _Val, size_t _Count,_locale_t _Locale);
+  _Check_return_
+  _CRTIMP
+  wchar_t *
+  __cdecl
+  wcstok_s(
+    _Inout_opt_z_ wchar_t *_Str,
+    _In_z_ const wchar_t *_Delim,
+    _Inout_ _Deref_prepost_opt_z_ wchar_t **_Context);
 
-#endif
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcserror_s(
+    _Out_writes_opt_z_(_SizeInWords) wchar_t *_Buf,
+    _In_ size_t _SizeInWords,
+    _In_ int _ErrNum);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  __wcserror_s(
+    _Out_writes_opt_z_(_SizeInWords) wchar_t *_Buffer,
+    _In_ size_t _SizeInWords,
+    _In_z_ const wchar_t *_ErrMsg);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsnset_s(
+    _Inout_updates_z_(_DstSizeInWords) wchar_t *_Dst,
+    _In_ size_t _DstSizeInWords,
+    _In_ wchar_t _Val,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsset_s(
+    _Inout_updates_z_(_SizeInWords) wchar_t *_Str,
+    _In_ size_t _SizeInWords,
+    _In_ wchar_t _Val);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcslwr_s(
+    _Inout_updates_z_(_SizeInWords) wchar_t *_Str,
+    _In_ size_t _SizeInWords);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcslwr_s_l(
+    _Inout_updates_z_(_SizeInWords) wchar_t *_Str,
+    _In_ size_t _SizeInWords,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsupr_s(
+    _Inout_updates_z_(_Size) wchar_t *_Str,
+    _In_ size_t _Size);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsupr_s_l(
+    _Inout_updates_z_(_Size) wchar_t *_Str,
+    _In_ size_t _Size,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  wcsncat_s(
+    _Inout_updates_z_(_DstSizeInChars) wchar_t *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const wchar_t *_Src,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsncat_s_l(
+    _Inout_updates_z_(_DstSizeInChars) wchar_t *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const wchar_t *_Src,
+    _In_ size_t _MaxCount,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  wcsncpy_s(
+    _Out_writes_z_(_DstSizeInChars) wchar_t *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const wchar_t *_Src,
+    _In_ size_t _MaxCount);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsncpy_s_l(
+    _Out_writes_z_(_DstSizeInChars) wchar_t *_Dst,
+    _In_ size_t _DstSizeInChars,
+    _In_z_ const wchar_t *_Src,
+    _In_ size_t _MaxCount,
+    _In_opt_ _locale_t _Locale);
+
+  _CRTIMP
+  wchar_t *
+  __cdecl
+  _wcstok_s_l(
+    _Inout_opt_z_ wchar_t *_Str,
+    _In_z_ const wchar_t *_Delim,
+    _Inout_ _Deref_prepost_opt_z_ wchar_t **_Context,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsset_s_l(
+    _Inout_updates_z_(_SizeInChars) wchar_t *_Str,
+    _In_ size_t _SizeInChars,
+    _In_ unsigned int _Val,
+    _In_opt_ _locale_t _Locale);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wcsnset_s_l(
+    _Inout_updates_z_(_SizeInChars) wchar_t *_Str,
+    _In_ size_t _SizeInChars,
+    _In_ unsigned int _Val,
+    _In_ size_t _Count,
+    _In_opt_ _locale_t _Locale);
+
+#endif /* _WSTRING_S_DEFINED */
 
 #ifdef __cplusplus
 }
 #endif
-#endif
-#endif
+
+#endif /* MINGW_HAS_SECURE_API */
+
+#endif /* _INC_STRING_S */