A newer version, safety commit

lang/m2/comp/scope.C

@@ -0,0 +1,62 @@
+/* S C O P E   M E C H A N I S M */
+
+static char *RcsId = "$Header$";
+
+#include	<assert.h>
+#include	<alloc.h>
+#include	"scope.h"
+
+static int maxscope;		/* maximum assigned scope number */
+
+struct scope *CurrentScope;
+
+/* STATICALLOCDEF "scope" */
+
+/*	Open a scope that is either open (automatic imports) or closed.
+	A closed scope is handled by adding an extra entry to the list
+	with scope number 0. This has two purposes: it makes scope 0
+	visible, and it marks the end of a visibility list.
+	Scope 0 is the pervasive scope, the one that is always visible.
+	A disadvantage of this method is that we cannot open scope 0
+	explicitly.
+*/
+open_scope(scopetype, scopenr)
+{
+	register struct scope *sc = new_scope();
+	register struct scope *sc1;
+
+	sc->sc_scope = scopenr == 0 ? ++maxscope : scopenr;
+	assert(scopetype == OPENSCOPE || scopetype == CLOSEDSCOPE);
+	sc1 = CurrentScope;
+	if (scopetype == CLOSEDSCOPE) {
+		sc1 = new_scope();
+		sc1->sc_scope = 0;			/* Pervasive scope nr */
+		sc1->next = CurrentScope;
+	}
+	sc->next = sc1;
+	CurrentScope = sc;
+}
+
+close_scope()
+{
+	register struct scope *sc = CurrentScope;
+
+	assert(sc != 0);
+	if (sc->next && (sc->next->sc_scope == 0)) {
+		struct scope *sc1 = sc;
+
+		sc = sc->next;
+		free_scope(sc1);
+	}
+	CurrentScope = sc->next;
+	free_scope(sc);
+}
+
+init_scope()
+{
+	register struct scope *sc = new_scope();
+
+	sc->sc_scope = 0;
+	sc->next = 0;
+	CurrentScope = sc;
+}