remove espie's double-linked-list based allocator and write a

similarily simple one from scratch, which however performs
better than espie's with AFREE_DEBUG enabled which took away
the benefit of the double-linked-list approach

all of (core) mksh is now MirOS licenced

lalloc.c

@@ -0,0 +1,86 @@
+#include "sh.h"
+
+__RCSID("$MirOS: src/bin/mksh/lalloc.c,v 1.1 2009/03/22 16:55:38 tg Exp $");
+
+struct lalloc {
+	struct lalloc *next;	/* entry pointer, must be first */
+	Area *group;		/* group backpointer */
+};
+
+static void findptr(struct lalloc **, struct lalloc **, char *, Area *);
+
+void
+ainit(Area *ap)
+{
+	ap->ent = NULL;
+}
+
+static void
+findptr(struct lalloc **lpp, struct lalloc **ppp, char *ptr, Area *ap)
+{
+	*lpp = (struct lalloc *)(ptr - sizeof (struct lalloc));
+	if ((*lpp)->group != ap)
+ notfound:
+		internal_errorf("pointer %p not in group %p", ptr, ap);
+	*ppp = (struct lalloc *)ap;
+	while ((*ppp)->next != *lpp)
+		if (((*ppp) = (*ppp)->next) == NULL)
+			goto notfound;
+}
+
+void *
+aresize(void *ptr, size_t numb, Area *ap)
+{
+	struct lalloc *lp, *pp;
+
+	if (numb >= SIZE_MAX - sizeof (struct lalloc))
+ failure:
+		internal_errorf("cannot allocate %lu data bytes",
+		    (unsigned long)numb);
+
+	if (ptr == NULL) {
+		pp = (struct lalloc *)ap;
+		lp = malloc(numb + sizeof (struct lalloc));
+	} else {
+		findptr(&lp, &pp, ptr, ap);
+		lp = realloc(lp, numb + sizeof (struct lalloc));
+	}
+	if (lp == NULL)
+		goto failure;
+	if (ptr == NULL) {
+		lp->group = ap;
+		lp->next = ap->ent;
+	}
+	pp->next = lp;
+	return ((char *)lp + sizeof (struct lalloc));
+}
+
+void
+afree(void *ptr, Area *ap)
+{
+	struct lalloc *lp, *pp;
+
+	if (ptr == NULL)
+		return;
+
+	findptr(&lp, &pp, ptr, ap);
+	pp->next = lp->next;
+	/* lp->group = NULL; */
+	free(lp);
+}
+
+void
+afreeall(Area *ap)
+{
+	struct lalloc *lp;
+
+	while ((lp = ap->ent) != NULL) {
+#ifndef MKSH_SMALL
+		if (lp->group != ap)
+			internal_errorf("rogue pointer in group %p", ap);
+#endif
+		ap->ent = lp->next;
+		/* lp->group = NULL; */
+		free(lp);
+	}
+}