bowman@reed.UUCP (Eric Bowman) (01/14/91)
Has someone, somewhere, sometime elucidated when to lock down a handle
object? (i.e. calling constructors, virtual functions, etc.)
Currently I'm proceeding somewhat by trial and error (with success...apparently)
but it seems like a sticky point.
Any references appreciated (d e v e l o p, etc.)
Thanks,
bobo
bowman@reed.{bitnet,UUCP,edu}
...!tektronix!reed!bowmananders@verity.com (Anders Wallgren) (01/15/91)
In article <15876@reed.UUCP>, bowman@reed (Eric Bowman) writes: >Has someone, somewhere, sometime elucidated when to lock down a handle >object? (i.e. calling constructors, virtual functions, etc.) > develop, issue 2, has an article by Curt Bianchi called "Using Objects Safely in Object Pascal." I've found that most of that article applies to C++ as well, and since reading it I can't recall having any problems with loose handles, and my income has more than tripled and my health improved greatly. Call now! anders
marc@Apple.COM (Mark Dawson) (01/15/91)
In article <15876@reed.UUCP> bowman@reed.UUCP (Eric Bowman) writes: >Has someone, somewhere, sometime elucidated when to lock down a handle >object? (i.e. calling constructors, virtual functions, etc.) > >Currently I'm proceeding somewhat by trial and error (with success...apparently) >but it seems like a sticky point. > >Any references appreciated (d e v e l o p, etc.) > I generally try to lock down a handle object when I'm calling procedures/ functions that use pointers to my object. For example, if you have an array x (Str255 x): GetName(this->x); Now if GetName(Str255 x) does something like this: char *z = new 2; x[0] = sprintf((char *)&x[1],"Hello world"); You could be in trouble--MPW C++ pushes the address of the array (x) onto the stack; after the new (or any toolbox call that can move memory) "this" may be moved, moving the address of the array "x". So now when you do the "x[0] = sprintf(..." statement, "x"'s address is no longer valid. The correct procedure would be to: HLock((Handle)this); GetName(this->x); HUnlock((Handle)this); I ran across this when I stress tested my own (MacApp/C++ based ) program using MacsBugs heap scrambling commands ("HS;ATHCA"). Hope this helps. Mark -- --------------------------------- Mark Dawson Service Diagnostic Engineering AppleLink: Dawson.M Apple says what it says; I say what I say. We're different ---------------------------------