6l: Aconv safety

Reference: /n/atom/patch/applied/ldaconvsafe
Date: Sun Aug 16 04:02:31 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/6l/list.c	Sun Aug 16 04:02:21 2015
+++ /sys/src/cmd/6l/list.c	Sun Aug 16 04:02:23 2015
@@ -50,12 +50,31 @@
 	return fmtstrcpy(fp, str);
 }
 
+static int lastaname;
+
+static void
+aconvinit(void)
+{
+	if(lastaname > 0)
+		return;
+	for(;; lastaname++)
+		if(strcmp(anames[lastaname], "LAST") == 0)
+			break;
+}
+
 int
 Aconv(Fmt *fp)
 {
+	char buf[32];
 	int i;
 
+	aconvinit();
+
 	i = va_arg(fp->args, int);
+	if(i < 0 || i > lastaname){
+		snprint(buf, sizeof buf, "[aname %d]", i);
+		return fmtstrcpy(fp, buf);
+	}
 	return fmtstrcpy(fp, anames[i]);
 }
 
@@ -354,7 +373,7 @@
 	print("%s: %s\n", tn, buf);
 
 	nerrors++;
-	if(nerrors > 20) {
+	if(nerrors > 20 && !debug['A']) {
 		print("too many errors\n");
 		errorexit();
 	}