Memo's weird problem-tdesc & "abrupt change"

Recently, the tdesc descriptor was used as a parameter reference for transmission. The length of the descriptor is normal before it is passed, but the length of the descriptor is out of bounds immediately after it is referenced. For memo, I don't know why it is compiled? Why is the stack (data is allocated on the stack, So it's weird )? Or why?

XXX: transformutf8tounicodel (* Buf, & unicodestring );
Cleanupstack: pushl (unicodestring );
// Parse body

// A problem occurs after the reference is passed. The unicodestring is hbufc *
Cstatusesobject * statusesobject = iparseengine-> parsestatusesobjectl (* unicodestring );
Cleanupstack: popanddestroy (unicodestring );