StringCbPrintfExA function (strsafe.h)

Writes formatted data to the specified string. The size of the destination buffer is provided to the function to ensure that it does not write past the end of this buffer.

StringCbPrintfEx adds to the functionality of StringCbPrintf by returning a pointer to the end of the destination string as well as the number of bytes left unused in that string. Flags may also be passed to the function for additional control.

StringCbPrintfEx is a replacement for the following functions:


  [out]           STRSAFE_LPSTR  pszDest,
  [in]            size_t         cbDest,
  [out, optional] STRSAFE_LPSTR  *ppszDestEnd,
  [out, optional] size_t         *pcbRemaining,
  [in]            DWORD          dwFlags,
  [in]            STRSAFE_LPCSTR pszFormat,


[out] pszDest


The destination buffer, which receives the formatted, null-terminated string created from pszFormat and its arguments.

[in] cbDest

Type: size_t

The size of the destination buffer, in bytes. This value must be sufficiently large to accommodate the final formatted string plus the terminating null character. The maximum number of bytes allowed is STRSAFE_MAX_CCH * sizeof(TCHAR).

[out, optional] ppszDestEnd


The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is copied into the destination buffer, this points to the terminating null character at the end of the string.

[out, optional] pcbRemaining

Type: size_t*

The number of unused bytes in pszDest, including those used for the terminating null character. If pcbRemaining is NULL, the count is not kept or returned.

[in] dwFlags


One or more of the following values.

Value Meaning
If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character.
Treat NULL string pointers like empty strings (TEXT("")).
If the function fails, the low byte of dwFlags (0) is used to fill the entire pszDest buffer, and the buffer is null-terminated. In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string returned is overwritten.
If the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.
As in the case of STRSAFE_NULL_ON_FAILURE, if the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.

[in] pszFormat


The format string. This string must be null-terminated. For more information, see Format Specification Syntax.


The arguments to be inserted into the pszFormat string.

Return value


This function can return one of the following values. It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.

Return code Description
There was sufficient space for the result to be copied to pszDest without truncation, and the buffer is null-terminated.
The value in cbDest is either 0 or larger than STRSAFE_MAX_CCH * sizeof(TCHAR), or the destination buffer is already full.
The copy operation failed due to insufficient buffer space. Depending on the value of dwFlags, the destination buffer may contain a truncated, null-terminated version of the intended result. In situations where truncation is acceptable, this may not necessarily be seen as a failure condition.

Note that this function returns an HRESULT value, unlike the functions that it replaces.


Compared to the functions it replaces, StringCbPrintfEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbPrintfEx always null-terminates a nonzero-length destination buffer.

Behavior is undefined if the strings pointed to by pszDest, pszFormat, or any argument strings overlap.

Neither pszFormat nor pszDest should be NULL unless the STRSAFE_IGNORE_NULLS flag is specified, in which case both may be NULL. However, an error due to insufficient space may still be returned even though NULL values are ignored.

StringCbPrintfEx can be used in its generic form, or in its more specific forms. The data type of the string determines the form of this function that you should use.

String Data Type String Literal Function
char "string" StringCbPrintfExA
TCHAR TEXT("string") StringCbPrintfEx
WCHAR L"string" StringCbPrintfExW


The strsafe.h header defines StringCbPrintfEx as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.


Requirement Value
Minimum supported client Windows XP with SP2 [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 with SP1 [desktop apps | UWP apps]
Target Platform Windows
Header strsafe.h

See also