Merge pull request #4855 from MicrosoftDocs/FromPublicMasterBranch

Confirm merge from FromPublicMasterBranch to main to sync with https://github.com/MicrosoftDocs/cpp-docs (branch main)

Author: huypub

docs/c-runtime-library/reference/strdec-wcsdec-mbsdec-mbsdec-l.md

@@ -15,7 +15,7 @@ ms.assetid: ae37c223-800f-48a9-ae8e-38c8d20af2dd
 Moves a string pointer back one character.
 
 > [!IMPORTANT]
-> **`mbsdec`** and **`mbsdec_l`** cannot be used in applications that execute in the Windows Runtime. For more information, see [CRT functions not supported in Universal Windows Platform apps](../../cppcx/crt-functions-not-supported-in-universal-windows-platform-apps.md).
+> **`_mbsdec`** and **`_mbsdec_l`** cannot be used in applications that execute in the Windows Runtime. For more information, see [CRT functions not supported in Universal Windows Platform apps](../../cppcx/crt-functions-not-supported-in-universal-windows-platform-apps.md).
 
 ## Syntax
 

docs/c-runtime-library/reference/wcstombs-wcstombs-l.md

@@ -64,6 +64,8 @@ If **`wcstombs`** successfully converts the multibyte string, it returns the num
 
 The **`wcstombs`** function converts the wide-character string pointed to by *`wcstr`* to the corresponding multibyte characters and stores the results in the *`mbstr`* array. The *`count`* parameter indicates the maximum number of bytes that can be stored in the multibyte output string (that is, the size of *`mbstr`*). In general, it isn't known how many bytes will be required when converting a wide-character string. Some wide characters will require only a single byte in the output string; others require 2 bytes. If there are 2 bytes in the multibyte output string for every wide character in the input string (including the wide character `NULL`), the result is guaranteed to fit.
 
+Starting in Windows 10 version 1803 (10.0.17134.0), the Universal C Runtime supports using a UTF-8 code page. Use `wcstombs(NULL, wcstr, 0)` to get the correct size that you'll need for the conversion because assuming that you'll need two bytes for every wide character may not be enough. For more information about UTF-8 support, see [UTF-8 support](setlocale-wsetlocale.md)
+
 If **`wcstombs`** encounters the wide-character `NULL` character (L'\0') either before or when *`count`* occurs, it converts it to an 8-bit 0 and stops. Thus, the multibyte character string at *`mbstr`* is null-terminated only if **`wcstombs`** encounters a wide-character `NULL` character during conversion. If the sequences pointed to by *`wcstr`* and *`mbstr`* overlap, the behavior of **`wcstombs`** is undefined.
 
 If the *`mbstr`* argument is `NULL`, **`wcstombs`** returns the required size in bytes of the destination string.