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From: gp@picuxa.UUCP (Greg Pasquariello X1190)
Newsgroups: comp.lang.c
Subject: MSC and stack manipulation
Message-ID: <325@picuxa.UUCP>
Date: Mon, 5-Oct-87 15:00:38 EDT
Article-I.D.: picuxa.325
Posted: Mon Oct  5 15:00:38 1987
Date-Received: Fri, 9-Oct-87 01:22:20 EDT
Organization: AT&T Information Systems, Parsippany NJ
Lines: 33
Keywords: MSC

Here is a question for anyone who cares to throw his stack in the ring.
When MSC 4.0 calls a function, it subtracts the amount of space needed
by local variables from the stack.  Why?  The 80x86 instructions subtract
two bytes from SP when a push is done anyway.  Therefore the MSC function
calls leave an unused gap in the stack equal to the count of bytes 
required by local variables.

	For example:

		func FOO1:	SP = 128
				CALL FOO2

		func FOO2(char, char):
				SP = 126
				BP = SP
				SP = SP - 2	/* WHY??? */
				.
				.
				.
				SP = BP
				RETURN

Unless I'm missing something, the SP = SP - 2 statement points the stack
two bytes below the last push.  Therefor the next push will put the value
of the register (whatever it may be) two bytes below the previous push
thus leaving a gap in the stack of two bytes.


Any answers will be appreciated.


Oh yeah, no flames please, if this sounds like a pathetically stupid 
question :-)