@let: add self-checks to symbol management code.

* symbol.c (remove_common, install): Check the sanity of the
installation and removal of parameter and alias symbols. This
is purely compile-time so the cycles are worth it.

1 files changed, 15 insertions, 2 deletions

diff --git a/symbol.c b/symbol.c
index 9f40568a..f2a0ad89 100644
--- a/symbol.c
+++ b/symbol.c
@@ -247,10 +247,16 @@ remove_common(NODE *p)
 	tmp = make_string(p->vname, strlen(p->vname));
 	tmp2 = in_array(table, tmp);
 
-	if (tmp2 != NULL && tmp2->dup_ent != NULL)
+	if (tmp2 == NULL) {
+		/* nothing: diagnosing this leads to certain false positives. */
+	} else if (tmp2->dup_ent == p) {
 		tmp2->dup_ent = tmp2->dup_ent->dup_ent;
-	else
+	} else if (tmp2->dup_ent == NULL && tmp2 == p) {
 		(void) assoc_remove(table, tmp);
+	} else {
+		fatal(_("LIFO local variable allocation not observed (p %p, found %p, dup %p)"),
+				p, tmp2, tmp2->dup_ent);
+	}
 
 	unref(tmp);
 }
@@ -436,10 +442,17 @@ install(const char *name, NODE *parm, NODETYPE type)
 	}
 
 	if (type == Node_param_list || type == Node_alias) {
+		NODE *dchk;
 		r->dup_ent = NULL;
 		prev = in_array(table, n_name);
 		if (prev == NULL)
 			goto simple;
+		if (prev == r)
+			fatal("primary symbol %s (%p/ type %d) entered twice into symbol table",
+				  r->vname, r, r->type);
+		for (dchk = prev->dup_ent; dchk != NULL; dchk = dchk->dup_ent)
+			if (dchk == r)
+				fatal("shadowing symbol entered twice into symbol table");
 		r->dup_ent = prev->dup_ent;
 		prev->dup_ent = r;
 		unref(n_name);