core: Add garbage collector/jam collector experiment.

* mes.c (gc, gc_loop, gc_copy, gc_move, gc_relocate_car,
  gc_relocate_cdr, gc_flip): New function.
* tests/gc-0.test: New file.

GNUmakefile

@@ -5,10 +5,10 @@ default: all
 	./configure
 
 OUT:=out
-CFLAGS:=-std=c99 -O3 -finline-functions
+#CFLAGS:=-std=c99 -O3 -finline-functions
 #CFLAGS:=-std=c99 -O0
 #CFLAGS:=-pg -std=c99 -O0
-#CFLAGS:=-std=c99 -O0 -g
+CFLAGS:=-std=c99 -O0 -g
 
 export BOOT
 ifneq ($(BOOT),)

mes.c

@@ -30,8 +30,13 @@
 #define DEBUG 0
 #define QUASIQUOTE 1
 //#define QUASISYNTAX 0
+#define GC 1
+//int ARENA_SIZE = 1024 * 1024 * 1024;
+//int ARENA_SIZE = 27000; // sizeof(scm) = 24
+int ARENA_SIZE = 10;
+int GC_SAFETY = 0;
 
-enum type {CHAR, FUNCTION, MACRO, NUMBER, PAIR, SCM, STRING, SYMBOL, REF, VALUES, VECTOR};
+enum type {CHAR, FUNCTION, MACRO, NUMBER, PAIR, SCM, STRING, SYMBOL, REF, VALUES, VECTOR, BROKEN_HEART};
 
 typedef struct scm_t* (*function0_t) (void);
 typedef struct scm_t* (*function1_t) (struct scm_t*);
@@ -144,10 +149,150 @@ cdr (scm *x)
   return x->cdr;
 }
 
+scm g_free = {NUMBER, .value=0};
+scm *g_cells;
+scm *g_news;
+
 scm *
 alloc (int n)
 {
+#if 0
+  // haha, where are we going to get our root, i.e., a=environment?
+  //if (g_free - g_cells + n >= ARENA_SIZE) gc ();
+  assert (g_free.value + n < ARENA_SIZE);
+  scm* x = &g_cells[g_free.value];
+  g_free.value += n;
+  return x;
+#else
   return (scm*)malloc(n*sizeof (scm));
+#endif
+}
+
+scm *
+gc_alloc (int n)
+{
+  assert (g_free.value + n < ARENA_SIZE);
+  scm* x = &g_cells[g_free.value];
+  g_free.value += n;
+  return x;
+}
+
+scm *
+gc (scm *a)
+{
+  fprintf (stderr, "***GC***\n");
+  g_free.value = 0;
+  gc_show ();
+  scm *new = gc_copy (a);
+  return gc_loop (new);
+}
+
+scm *
+gc_loop (scm *new)
+{
+  while (new - g_news < g_free.value)
+    {
+      gc_show ();
+      if (new->type == PAIR
+          || new->type == REF
+          || new->type == STRING
+          || new->type == SYMBOL)
+        {
+          scm *car = gc_copy (new->car);
+          gc_relocate_car (new, car);
+        }
+      if (new->type == PAIR)
+        {
+          scm *cdr = gc_copy (new->cdr);
+          gc_relocate_cdr (new, cdr);
+        }
+      new++;
+    }
+  return gc_flip ();
+}
+
+scm *
+gc_copy (scm *old)
+{
+  if (old->type == BROKEN_HEART) return old->car;
+  if (old->type == SCM) return old;
+  scm *new = &g_news[g_free.value++];
+  *new = *old;
+  if (new->type == VECTOR)
+    for (int i=0; i<old->length; i++)
+      *(new+i+1) = old->vector[i];
+  old->type = BROKEN_HEART;
+  old->car = new;
+  return new;
+}
+
+scm *
+gc_move (scm* dest, scm *src)
+{
+  *dest = *src;
+}
+
+scm *
+gc_relocate_car (scm *new, scm *car)
+{
+  new->car = car;
+  return &scm_unspecified;
+}
+
+scm *
+gc_relocate_cdr (scm *new, scm *cdr)
+{
+  new->cdr = cdr;
+  return &scm_unspecified;
+}
+
+scm *
+gc_flip ()
+{
+  scm *cells = g_cells;
+  g_cells = g_news;
+  g_news = cells;
+  (g_cells-1)->vector = g_news;
+  (g_news-1)->vector = g_cells;
+  return &scm_unspecified;
+}
+
+scm *
+gc_show ()
+{
+  fprintf (stderr, "cells: ");
+  display_ (stderr, g_cells-1);
+  fprintf (stderr, "\n");
+  fprintf (stderr, "news: ");
+  display_ (stderr, g_news-1);
+  fprintf (stderr, "\n");
+  return &scm_unspecified;
+}
+
+scm *
+gc_make_cell (scm *type, scm *car, scm *cdr)
+{
+  scm *x = gc_alloc (1);
+  assert (type->type == NUMBER);
+  x->type = type->value;
+  if (type->value == CHAR || type->value == NUMBER) {
+    if (car) x->car = car->car;
+    if (cdr) x->cdr = cdr->cdr;
+  } else {
+    x->car = car;
+    x->cdr = cdr;
+  }
+  return x;
+}
+
+scm *
+gc_make_vector (scm *n)
+{
+  scm t = {NUMBER, .value=VECTOR};
+  scm *v = gc_alloc (n->value);
+  scm *x = gc_make_cell (&t, (scm*)(long)n->value, v);
+  for (int i=0; i<n->value; i++) x->vector[i] = *vector_entry (&scm_unspecified);
+  return x;
 }
 
 scm *
@@ -415,6 +560,7 @@ apply_env (scm *fn, scm *x, scm *a)
 scm *
 eval_env (scm *e, scm *a)
 {
+  /////if (g_free.value + GC_SAFETY > ARENA_SIZE) gc (a);
   switch (e->type)
     {
     case PAIR:
@@ -812,9 +958,12 @@ force_output (scm *p) ///((arity . n))
   fflush (f);
 }
 
+int display_depth = 1000;
 scm *
 display_helper (FILE* f, scm *x, bool cont, char const *sep, bool quote)
 {
+  if (!display_depth) return &scm_unspecified;
+  display_depth--;
   scm *r;
   fprintf (f, "%s", sep);
   switch (x->type)
@@ -881,6 +1030,7 @@ display_helper (FILE* f, scm *x, bool cont, char const *sep, bool quote)
       }
     case REF: display_helper (f, x->ref, cont, "", true); break;
     case FUNCTION: fprintf (f, "#<procedure %s>", x->name); ;break;
+    case BROKEN_HEART: fprintf (f, "<3"); break;
     default:
       if (x->string)
         {
@@ -1125,6 +1275,20 @@ mes_environment () ///((internal))
 {
   scm *a = &scm_nil;
 
+  // setup GC
+  g_cells = (scm*)malloc (ARENA_SIZE*sizeof(scm));
+  g_news = (scm*)malloc (ARENA_SIZE*sizeof(scm));
+  g_cells[0].type = VECTOR;
+  g_cells[0].length = ARENA_SIZE - 1;
+  g_cells[0].vector = &g_cells[1];
+  g_news[0].type = VECTOR;
+  g_news[0].length = ARENA_SIZE - 1;
+  g_news[0].vector = &g_news[1];
+
+  a = add_environment (a, "%free", &g_free);
+  a = add_environment (a, "%the-cells", g_cells++);
+  a = add_environment (a, "%new-cells", g_news++);
+
   #include "mes.symbols.i"
 
 #if BOOT

tests/gc-0.test

@@ -0,0 +1,41 @@
+#! /bin/sh
+# -*-scheme-*-
+echo ' ()' | cat $($(dirname $0)/../scripts/include.mes $0) $0 /dev/stdin | $(dirname $0)/../scripts/mes "$@"
+#paredit:||
+exit $?
+!#
+
+;;; -*-scheme-*-
+
+;;; Mes --- Maxwell Equations of Software
+;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;;
+;;; This file is part of Mes.
+;;;
+;;; Mes is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; Mes is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with Mes.  If not, see <http://www.gnu.org/licenses/>.
+
+(define zero (gc-make-cell 2 0 0))
+(define one (gc-make-cell 2 0 1))
+(display %the-cells) (newline)
+(define pair (gc-make-cell 3 zero one)) 
+(display "cells:") (display %the-cells) (newline)
+(define zero-list (gc-make-cell 3 zero '()))
+(define v (gc-make-vector 1))
+(vector-set! v 0 88)
+(define zero-v-list (gc-make-cell 3 v zero-list))
+(define list (gc-make-cell 3 (gc-make-cell 3 zero one) zero-v-list))
+(gc list)
+(display "gc done\n")
+(display "scm old:") (display %new-cells) (newline)
+(display "scm cells:") (display %the-cells) (newline)