About Strsafe.h

Poor buffer handling is implicated in many security issues that involve buffer overruns. The functions defined in Strsafe.h provide additional processing for proper buffer handling in your code. For this reason, they are intended to replace their built-in C/C++ counterparts as well as specific Windows implementations. Strsafe.h is available in the Windows SDK starting with Windows XP with Service Pack 2 (SP2).

The advantages of the Strsafe functions include:

• The size of the destination buffer is always provided to the function to ensure that the function does not write past the end of the buffer.

• Buffers are guaranteed to be null-terminated, even if the operation truncates the intended result.

• All functions return an HRESULT value, with only one possible success code (S_OK).

• Each function is available in a corresponding character count ("cch") or byte count ("cb") version.

• Most functions have an extended ("Ex") version available for advanced functionality.

See the following sections for details.

• Character Count Functions
• Byte Count Functions
• Using Strsafe.h
• Related topics

Character Count Functions

The following functions use a character count rather than a byte count.

Function	Replaces
StringCchCat StringCchCatEx	strcat, wcscat, _tcscat lstrcat StrCat StrCatBuff
StringCchCatN StringCchCatNEx	strncat StrNCat
StringCchCopy StringCchCopyEx	strcpy, wcscpy, _tcscpy lstrcpy StrCpy
StringCchCopyN StringCchCopyNEx	strncpy, wcsncpy, _tcsncpy
StringCchGets StringCchGetsEx	gets, _getws, _getts
StringCchPrintf StringCchPrintfEx	sprintf, swprintf, _stprintf wsprintf wnsprintf _snprintf, _snwprintf, _sntprintf
StringCchVPrintf StringCchVPrintfEx	vsprintf, vswprintf, _vstprintf vsnprintf, _vsnwprintf, _vsntprintf wvsprintf wvnsprintf ,
StringCchLength	strlen, wcslen, _tcslen

 

Byte Count Functions

The following functions use a byte count rather than a character count.

Function	Replaces
StringCbCat StringCbCatEx	strcat, wcscat, _tcscat lstrcat StrCat StrCatBuff
StringCbCatN StringCbCatNEx	strncat StrNCat
StringCbCopy StringCbCopyEx	strcpy, wcscpy, _tcscpy lstrcpy StrCpy
StringCbCopyN StringCbCopyNEx	strncpy, wcsncpy, _tcsncpy
StringCbGets StringCbGetsEx	gets, _getws, _getts
StringCbPrintf StringCbPrintfEx	sprintf, swprintf, _stprintf wsprintf wnsprintf _snprintf, _snwprintf, _sntprintf
StringCbVPrintf StringCbVPrintfEx	vsprintf, vswprintf, _vstprintf vsnprintf, _vsnwprintf, _vsntprintf wvsprintf wvnsprintf
StringCbLength	strlen, wcslen, _tcslen

 

Using Strsafe.h

• To use the Strsafe functions inline, include the header file as shown here, following the #include statements for all other header files.

  #include <strsafe.h>

• To use the functions in library form, include the following statement before including Strsafe.h. However, it is recommended that you use the inline functions.

  #define STRSAFE_LIB

  Note

  : The following functions must be used as inline functions: StringCbGets, StringCbGetsEx, StringCchGets, and StringCchGetsEx.

   

• When you include Strsafe.h in your file, the older functions replaced by the Strsafe.h functions will be deprecated. Attempts to use these older functions will result in a compiler error telling you to use the newer functions. If you want to override this behavior, include the following statement before including Strsafe.h.

  #define STRSAFE_NO_DEPRECATE

• To allow only character count functions, include the following statement before including Strsafe.h.

  #define STRSAFE_NO_CB_FUNCTIONS

• To allow only byte count functions, include the following statement before including Strsafe.h.

  #define STRSAFE_NO_CCH_FUNCTIONS

  Note

  You can define STRSAFE_NO_CB_FUNCTIONS or STRSAFE_NO_CCH_FUNCTIONS, but not both.

   

• Some Strsafe functions have locale-aware versions. By default, the header does not declare these functions. To enable these declarations, include the following macro statement before including Strsafe.h.

  #define STRSAFE_LOCALE_FUNCTIONS

• The maximum supported string length is 2,147,483,647 (STRSAFE_MAX_CCH) characters, either ANSI or Unicode.

Related topics

Strsafe Functions