[DUG] Reference counting

[Rohit Gupta]

I cant see how it can be safe.  I was stumped as well when I wanted 
to send a string in a message.  I had to abandon my ideas....  :-( Let 
me know if you have any joy.

From:           	"Paul Lowman" <paul_lowman at xtra.co.nz>
To:             	"Delphi List" <delphi at delphi.org.nz>
Date sent:      	Thu, 24 Nov 2005 16:22:04 +1300
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Subject:        	[DUG] Reference counting
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Heres one for the gurus -

Assume  a long string variable is declared locally to a method and is
assigned a string and the string variable is then typecast as an integer and
used in - say - a windows message by assigning it to the message lparam.

The question is when the message is received by another form / thread is it
valid to then typecast the lparam back to a string and use it ?

I have tried many variations of this scenario and it seems to work OK but am
uneasy about whether or not this is safe. I assume it isn't as the local
string variable (which points to the actual string) is on the stack and is
not maintained after the method is exited but what I really am concerned
about is the reference count for the string - has it been increased by
typecasting it to an integer / pointer whatever ...

I have used some of Marco Cantu's code to try and examine the strings
reference count and it always appears to be -1 if the string is a local
variable although it works correctly for field or global.

All very confusing :-)

I would like to know how the code knows when to inc / dec / dispose the
stirng / array reference count.

Cheers

Paul Lowman

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Regards

Rohit

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