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To: 9front@9front.org
Subject: Re: [9front] x509.c for ape in libsec.a
Date: Thu, 9 Jul 2020 21:12:40 -0700
From: ori@eigenstate.org
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X-Bullshit: lossless pipelining optimizer 

>> The cpp time stamped Oct 7, 2019 does right thing, but that of Jul 17, 
>> 2020 fails.
> s/Jul 17 2020/Jun 17 2020/
> 
> sorry
> 
> Kenji

Alright, I think I have a fix for this issue. We need to put the
macro into the hideset before doing the final pass, or there's
potential for macro expansion to cycle in some cases.

	expand(A) => B
	expand(B) => A
	expand(A) => B
	...

This diff seems to work, but it's late and it needs more testing.
I've run it against our base system, netsurf, and perl.

diff -r 7bd3f3b9dc76 sys/src/cmd/cpp/macro.c
--- a/sys/src/cmd/cpp/macro.c	Sun Jul 05 22:15:02 2020 +0200
+++ b/sys/src/cmd/cpp/macro.c	Thu Jul 09 21:10:36 2020 -0700
@@ -169,15 +169,32 @@
 		}
 		if (np->flag&ISMAC)
 			builtin(trp, np->val);
-		else {
+		else
 			expand(trp, np);
-		}
 		tp = trp->tp;
 	}
 	if (flag)
 		unsetsource();
 }
 
+void
+hsspread(Tokenrow *ntr, Tokenrow *trp, Nlist *np)
+{
+	Token *tp;
+	int hs;
+
+	hs = newhideset(trp->tp->hideset, np);
+	/* distribute hidesets */
+	for (tp=ntr->bp; tp<ntr->lp; tp++) {
+		if (tp->type!=NAME)
+			continue;
+		if (tp->hideset==0)
+			tp->hideset = hs;
+		else
+			tp->hideset = unionhideset(tp->hideset, hs);
+	}
+}
+
 /*
  * Expand the macro whose name is np, at token trp->tp, in the tokenrow.
  * Return trp->tp at the first token next to be expanded
@@ -186,17 +203,18 @@
 void
 expand(Tokenrow *trp, Nlist *np)
 {
+	static int depth;
 	Tokenrow ntr;
 	int ntokc, narg, i;
-	Token *tp;
 	Tokenrow *atr[NARG+1];
-	int hs;
 
+	depth++;
 	copytokenrow(&ntr, np->vp);		/* copy macro value */
 	if (np->ap==NULL) {			/* parameterless */
 		ntokc = 1;
 		/* substargs for handling # and ## */
 		atr[0] = nil;
+		hsspread(&ntr, trp, np);
 		substargs(np, &ntr, atr);
 	} else {
 		ntokc = gatherargs(trp, atr, (np->flag&ISVARMAC) ? rowlen(np->ap) : 0, &narg);
@@ -215,16 +233,9 @@
 			dofree(atr[i]->bp);
 			dofree(atr[i]);
 		}
+		hsspread(&ntr, trp, np);
 	}
-	hs = newhideset(trp->tp->hideset, np);
-	for (tp=ntr.bp; tp<ntr.lp; tp++) {	/* distribute hidesets */
-		if (tp->type==NAME) {
-			if (tp->hideset==0)
-				tp->hideset = hs;
-			else
-				tp->hideset = unionhideset(tp->hideset, hs);
-		}
-	}
+
 	ntr.tp = ntr.bp;
 	insertrow(trp, ntokc, &ntr);
 	trp->tp -= rowlen(&ntr);
@@ -343,6 +354,7 @@
 	}
 	return 0;
 }
+
 /*
  * substitute the argument list into the replacement string
  *  This would be simple except for ## and #
@@ -408,7 +420,7 @@
 				if(ttr.tp->hideset == 0)
 					ttr.tp->hideset = hs;
 				else
-					ttr.tp->hideset = unionhideset(ttr.tp->hideset, hs);
+					ttr.tp->hideset = unionhideset(rtr->tp->hideset, hs);
 				expandrow(&ttr, (char*)np->name);
 				for(tp = ttr.bp; tp != ttr.lp; tp++)
 					if(tp->type == COMMA)