DOCERR: DdeCreateStringHandle() lpszString param

• Microsoft Windows Software Development Kit (SDK) versions 3.1
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

SUMMARY

The documentation for the DdeCreateStringHandle() function in the Windows 3.1 Software Development Kit (SDK) "Programmer's Reference, Volume 2: Functions" incorrectly states that the lpszString parameter may point to a buffer of a null-terminated string of any length, when the string is actually limited to 255 characters.

DDEML string-management functions are internally implemented using global atom functions. DdeCreateStringHandle() in particular, internally calls GlobalAddAtom(), and therefore inherits the same limitation as atoms to a maximum of 255 characters in length.

MORE INFORMATION

DDEML applications use string handles extensively to carry out DDE tasks. To obtain a string handle for a string, an application calls DdeCreateStringHandle(). This function registers the string with the system by adding the string to the global atom table, and returns a unique value identifying the string.

The global atom table table in Windows can maintain strings that are less than or equal to 255 characters in length. Any attempt to add a string of greater length to this global atom table will fail. Hence, a call to DdeCreateStringHandle() fails for strings over 255 characters long.

This limitation is by design. DDEML applications that use the DdeCreateStringHandle() function should conform to the 255-character limit.

This limitation has been preserved on the Windows NT version of DDEML for compatibility reasons.