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From: wmm@sdti.UUCP (William M. Miller)
Newsgroups: comp.lang.c++
Subject: Stack overflow compiling y.tab.c
Message-ID: <131@sdti.UUCP>
Date: Wed, 30-Sep-87 01:29:56 EDT
Article-I.D.: sdti.131
Posted: Wed Sep 30 01:29:56 1987
Date-Received: Mon, 5-Oct-87 07:14:53 EDT
Reply-To: wmm@sdti.UUCP (William M. Miller)
Organization: Software Development Technologies, Sudbury MA
Lines: 35


A couple of weeks ago, someone posted an article saying that they had
pretty much succesfully ported cfront, except that when they ran it on the
y.tab file it bombed with a stack overflow.  I posted a reply at that time,
but have only recently found out that our net feed was swallowing our
postings.  I am hence reposting the information; unfortunately I have lost
the original message and cannot give a reference.

I had the same experience when porting cfront to OS/2.  What I eventually
ended up doing was to split the huge switch statement in yyparse into
a bunch of 32-case pieces, i.e.,

	switch(yytmp) {
	case 1:
		...
	case 254:...
	}

became

	if (yytmp < 32) switch(yytmp) {
	case 1:
		...
	case 31:...
	} else if (yytmp < 64) switch(yytmp) {
	case 32:

etc.  It's not pretty, but at least it compiles without stack overflow now.
(I haven't any idea *why* large switch statements use up lots of stack space,
but they do.)
-- 
Non-disclaimer:  My boss and I always see eye-to-eye (every time I look in
the mirror).

...!genrad!mrst!sdti!wmm