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_strdup, _wcsdup, _mbsdup

Duplicates strings.

Important note Important

_mbsdup cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported with /ZW.

char *_strdup(
   const char *strSource 
wchar_t *_wcsdup(
   const wchar_t *strSource 
unsigned char *_mbsdup(
   const unsigned char *strSource 


Null-terminated source string.

Each of these functions returns a pointer to the storage location for the copied string or NULL if storage cannot be allocated.

The _strdup function calls malloc to allocate storage space for a copy of strSource and then copies strSource to the allocated space.

_wcsdup and _mbsdup are wide-character and multibyte-character versions of _strdup. The arguments and return value of _wcsdup are wide-character strings; those of _mbsdup are multibyte-character strings. These three functions behave identically otherwise.

Generic-Text Routine Mappings

TCHAR.H routine

_UNICODE & _MBCS not defined

_MBCS defined

_UNICODE defined





Because _strdup calls malloc to allocate storage space for the copy of strSource, it is good practice always to release this memory by calling the free routine on the pointer that's returned by the call to _strdup.

If _DEBUG and _CRTDBG_MAP_ALLOC are defined, _strdup and _wcsdup are replaced by calls to _strdup_dbg and _wcsdup_dbg to allow for debugging memory allocations. For more information, see _strdup_dbg, _wcsdup_dbg.


Required header




<string.h> or <wchar.h>



For additional compatibility information, see Compatibility.

// crt_strdup.c

#include <string.h>
#include <stdio.h>

int main( void )
   char buffer[] = "This is the buffer text";
   char *newstring;
   printf( "Original: %s\n", buffer );
   newstring = _strdup( buffer );
   printf( "Copy:     %s\n", newstring );
   free( newstring );
Original: This is the buffer text
Copy:     This is the buffer text