StringCbCatA function (strsafe.h)

Concatenates one string to another 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.

StringCbCat is a replacement for the following functions:


  [in, out] STRSAFE_LPSTR  pszDest,
  [in]      size_t         cbDest,
  [in]      STRSAFE_LPCSTR pszSrc


[in, out] pszDest


The string to which pszSrc is to be concatenated, and that will receive the entire resultant string. The string at pszSrc is added to the end of the string at pszDest.

[in] cbDest

Type: size_t

The size of the destination buffer, in bytes. This value must consider the length of pszSrc plus the length of pszDest plus the terminating null character. The maximum number of bytes allowed is STRSAFE_MAX_CCH * sizeof(TCHAR).

[in] pszSrc


The source string that is to be concatenated to the end of pszDest. This string must be null-terminated.

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
Source data was present, the strings were fully concatenated without truncation, and the resultant destination buffer is null-terminated.
The value in cbDest is either less than sizeof(TCHAR) or larger than the maximum allowed value.
The concatenation operation failed due to insufficient buffer space. The destination buffer contains 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.


StringCbCat provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. It always null-terminates and never overflows a valid destination buffer, even if the contents of the source string change during the operation.

StringCbCat 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, as shown in the following table.

String Data Type String Literal Function
char "string" StringCbCatA
TCHAR TEXT("string") StringCbCat
WCHAR L"string" StringCbCatW

Behavior is undefined if the strings pointed to by pszSrc and pszDest overlap.

Neither pszSrc nor pszDest should be NULL. See StringCbCatEx if you require the handling of null string pointer values.


The strsafe.h header defines StringCbCat 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.


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