Getbuffer and releasebuffer of cstring

The cstring in MFC is the ATL version.

See the followingCode:

Cstring STR = _ T ("123 ");
Lptstr P = Str. getbuffer (100 );
_ Tcscpy_s (p, 100, _ T ("ABCD "));
Assert (Str. getlength () = 3); // length still 3
Str. releasebuffer (); // surplus memory released, P is now invalid.
Assert (Str. getlength () = 4); // length now is 4

The string length obtained before releasebuffer is incorrect. The value of P after releasebuffer is invalid.

I often use sdks to write codes. It is not unreasonable to keep an eye on MFC.