OpenEuphoria

Re: Communicating processes using WM_COPYDATA

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Apr 02, 2005
• 667 views

On Fri, 01 Apr 2005 13:00:07 -0800, Bernie Ryan
<guest at RapidEuphoria.com> wrote:

>Pete:
>  When ever you receive a pointer to some data from
>  windows I read somewhere that you must immediately
>  make a copy of the data when you receive the message
>  because the data will no longer be valid on the next message.
I did it immediately. The case was P asking Q for a string:

--(NB: I've deleted the actual code, this is best recollection)
Q:
	elsif msg = CD_FILE then
		text=string&0
		mem=allocate(length(text))
--		?mem
		poke(mem,text)
		return {mem}

P:
	poke4(CDS,{CD_FILE,0,0})
	mem=c_func(xSendMessage,{hwnd, WM_COPYDATA, NULL, CDS})
--	?mem
	text=peek_string(mem)	-- <<== //**CRASHES**//

The peek() crashed no matter what; the memory address was correct (I
even tried a hard-coded length). Are you saying that peek in this way
may sometimes work?

Steadily getting even more confused, if that is possible,
Pete

PS lest anyone misinterpret, this is not about the RDS implementation
of peek and poke, but about what is and what is not a valid memory
address under the windows OS, I think.