diff --git a/Makefile b/Makefile
index 6c28e271..d5ae1e4f 100644
--- a/Makefile
+++ b/Makefile
@@ -9,21 +9,17 @@ LIBDIR=$(PREFIX)/lib
 INCDIR=$(PREFIX)/include/chibi-scheme
 MODDIR=$(PREFIX)/share/chibi-scheme
 
-LDFLAGS=-lm
+LDFLAGS=-lm #-lgc -L/opt/local/lib
 
-# -Oz for smaller size on darwin
-CFLAGS=-Wall -O2 -g #-save-temps
+CFLAGS=-Wall -O2 -g #-I/opt/local/include #-save-temps
 
-./gc/gc.a: ./gc/alloc.c
-	cd gc && make
-
-sexp.o: sexp.c gc.c sexp.h config.h defaults.h Makefile
+sexp.o: sexp.c gc.c sexp.h config.h Makefile
 	gcc -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-eval.o: eval.c debug.c opcodes.c eval.h sexp.h config.h defaults.h Makefile
+eval.o: eval.c debug.c opcodes.c eval.h sexp.h config.h Makefile
 	gcc -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
-main.o: main.c eval.c debug.c opcodes.c eval.h sexp.h config.h defaults.h Makefile
+main.o: main.c eval.c debug.c opcodes.c eval.h sexp.h config.h Makefile
 	gcc -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
 
 chibi-scheme: main.o sexp.o
diff --git a/config.h b/config.h
index 84ee7941..bb14e68b 100644
--- a/config.h
+++ b/config.h
@@ -14,8 +14,8 @@
 /* uncomment this if you only want fixnum support */
 /* #define USE_FLONUMS 0 */
 
-/* uncomment this if you want immediate flonums */
-#define USE_IMMEDIATE_FLONUMS 1
+/* uncomment this if you want immediate flonums (experimental) */
+/* #define USE_IMMEDIATE_FLONUMS 1 */
 
 /* uncomment this if you don't need extended math operations */
 /* #define USE_MATH 0 */
@@ -32,9 +32,75 @@
 /* uncomment this to disable string ports */
 /* #define USE_STRING_STREAMS 0 */
 
-/* uncomment this to disable a small optimization for let */
-/* #define USE_FAST_LET 0 */
+/* uncomment this to disable stack checks */
+/* #define USE_CHECK_STACK 0 */
 
 /* uncomment this to enable debugging utilities */
 /* #define USE_DEBUG 1 */
 
+/************************************************************************/
+/*         DEFAULTS - DO NOT MODIFY ANYTHING BELOW THIS LINE            */
+/************************************************************************/
+
+#if HAVE_ERR_H
+#include <err.h>
+#else
+/* requires msg be a string literal, and at least one argument */
+#define errx(code, msg, ...) (fprintf(stderr,msg"\n",__VA_ARGS__), exit(code))
+#endif
+
+#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__DragonFly__) || defined(__OpenBSD__)
+#define SEXP_BSD 1
+#else
+#define SEXP_BSD 0
+#define _GNU_SOURCE
+#endif
+
+#ifndef USE_BOEHM
+#define USE_BOEHM 0
+#endif
+
+#ifndef USE_MALLOC
+#define USE_MALLOC 0
+#endif
+
+#ifndef USE_DEBUG_GC
+#define USE_DEBUG_GC 0
+#endif
+
+#ifndef USE_FLONUMS
+#define USE_FLONUMS 1
+#endif
+
+#ifndef USE_IMMEDIATE_FLONUMS
+#define USE_IMMEDIATE_FLONUMS 0
+#endif
+
+#ifndef USE_MATH
+#define USE_MATH 1
+#endif
+
+#ifndef USE_WARN_UNDEFS
+#define USE_WARN_UNDEFS 1
+#endif
+
+#ifndef USE_HUFF_SYMS
+#define USE_HUFF_SYMS 1
+#endif
+
+#ifndef USE_HASH_SYMS
+#define USE_HASH_SYMS 1
+#endif
+
+#ifndef USE_DEBUG
+#define USE_DEBUG 1
+#endif
+
+#ifndef USE_STRING_STREAMS
+#define USE_STRING_STREAMS 1
+#endif
+
+#ifndef USE_CHECK_STACK
+#define USE_CHECK_STACK 1
+#endif
+
diff --git a/defaults.h b/defaults.h
deleted file mode 100644
index 7ac2d12b..00000000
--- a/defaults.h
+++ /dev/null
@@ -1,70 +0,0 @@
-/*  defaults.h -- defaults for unspecified configs       */
-/*  Copyright (c) 2009 Alex Shinn.  All rights reserved. */
-/*  BSD-style license: http://synthcode.com/license.txt  */
-
-#if HAVE_ERR_H
-#include <err.h>
-#else
-/* requires msg be a string literal, and at least one argument */
-#define errx(code, msg, ...) (fprintf(stderr,msg"\n",__VA_ARGS__), exit(code))
-#endif
-
-#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__DragonFly__) || defined(__OpenBSD__)
-#define SEXP_BSD 1
-#else
-#define SEXP_BSD 0
-#define _GNU_SOURCE
-#endif
-
-#ifndef USE_BOEHM
-#define USE_BOEHM 0
-#endif
-
-#ifndef USE_MALLOC
-#define USE_MALLOC 0
-#endif
-
-#ifndef USE_DEBUG_GC
-#define USE_DEBUG_GC 0
-#endif
-
-#ifndef USE_FLONUMS
-#define USE_FLONUMS 1
-#endif
-
-#ifndef USE_IMMEDIATE_FLONUMS
-#define USE_IMMEDIATE_FLONUMS 0
-#endif
-
-#ifndef USE_MATH
-#define USE_MATH 1
-#endif
-
-#ifndef USE_WARN_UNDEFS
-#define USE_WARN_UNDEFS 1
-#endif
-
-#ifndef USE_HUFF_SYMS
-#define USE_HUFF_SYMS 1
-#endif
-
-#ifndef USE_HASH_SYMS
-#define USE_HASH_SYMS 1
-#endif
-
-#ifndef USE_DEBUG
-#define USE_DEBUG 1
-#endif
-
-#ifndef USE_STRING_STREAMS
-#define USE_STRING_STREAMS 1
-#endif
-
-#ifndef USE_FAST_LET
-#define USE_FAST_LET 1
-#endif
-
-#ifndef USE_CHECK_STACK
-#define USE_CHECK_STACK 0
-#endif
-
diff --git a/eval.c b/eval.c
index e92178e7..e7515c46 100644
--- a/eval.c
+++ b/eval.c
@@ -1310,8 +1310,10 @@ sexp vm (sexp ctx, sexp proc) {
     goto make_call;
   case OP_CALL:
 #if USE_CHECK_STACK
-    if (top >= INIT_STACK_SIZE)
-      sexp_raise("out of stack space", SEXP_NULL);
+    if (top+16 >= INIT_STACK_SIZE) {
+      fprintf(stderr, "out of stack space\n");
+      exit(70);
+    }
 #endif
     i = sexp_unbox_integer(_WORD0);
     tmp1 = _ARG1;
@@ -1550,9 +1552,9 @@ sexp vm (sexp ctx, sexp proc) {
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_add(ctx, _ARG1, _ARG2);
     else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_fp_add(ctx, _ARG1, sexp_integer_to_flonum(ctx, _ARG2));
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) + (double)sexp_unbox_integer(_ARG2));
     else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_add(ctx, sexp_integer_to_flonum(ctx, _ARG1), _ARG2);
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) + sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("+: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     top--;
@@ -1564,9 +1566,9 @@ sexp vm (sexp ctx, sexp proc) {
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_sub(ctx, _ARG1, _ARG2);
     else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_fp_sub(ctx, _ARG1, sexp_integer_to_flonum(ctx, _ARG2));
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) - (double)sexp_unbox_integer(_ARG2));
     else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_sub(ctx, sexp_integer_to_flonum(ctx, _ARG1), _ARG2);
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) - sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("-: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     top--;
@@ -1578,9 +1580,9 @@ sexp vm (sexp ctx, sexp proc) {
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_mul(ctx, _ARG1, _ARG2);
     else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_fp_mul(ctx, _ARG1, sexp_integer_to_flonum(ctx, _ARG2));
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) * (double)sexp_unbox_integer(_ARG2));
     else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_mul(ctx, sexp_integer_to_flonum(ctx, _ARG1), _ARG2);
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) * sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("*: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     top--;
@@ -1588,17 +1590,22 @@ sexp vm (sexp ctx, sexp proc) {
   case OP_DIV:
     if (_ARG2 == sexp_make_integer(0))
       sexp_raise("divide by zero", SEXP_NULL);
-    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_fp_div(ctx,
-                          sexp_integer_to_flonum(ctx, _ARG1),
-                          sexp_integer_to_flonum(ctx, _ARG2));
+    if (sexp_integerp(_ARG1) && sexp_integerp(_ARG2)) {
+#if USE_FLONUMS
+      _ARG1 = sexp_integer_to_flonum(ctx, _ARG1);
+      _ARG2 = sexp_integer_to_flonum(ctx, _ARG2);
+      _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
+#else
+      _ARG2 = sexp_fx_div(_ARG1, _ARG2);
+#endif
+    }
 #if USE_FLONUMS
     else if (sexp_flonump(_ARG1) && sexp_flonump(_ARG2))
       _ARG2 = sexp_fp_div(ctx, _ARG1, _ARG2);
     else if (sexp_flonump(_ARG1) && sexp_integerp(_ARG2))
-      _ARG2 = sexp_fp_div(ctx, _ARG1, sexp_integer_to_flonum(ctx, _ARG2));
+      _ARG2 = sexp_make_flonum(ctx, sexp_flonum_value(_ARG1) / (double)sexp_unbox_integer(_ARG2));
     else if (sexp_integerp(_ARG1) && sexp_flonump(_ARG2))
-      _ARG2 = sexp_fp_div(ctx, sexp_integer_to_flonum(ctx, _ARG1), _ARG2);
+      _ARG2 = sexp_make_flonum(ctx, (double)sexp_unbox_integer(_ARG1) / sexp_flonum_value(_ARG2));
 #endif
     else sexp_raise("/: not a number", sexp_list2(ctx, _ARG1, _ARG2));
     top--;
@@ -1804,7 +1811,7 @@ static sexp sexp_open_input_file (sexp ctx, sexp path) {
   if (! in)
     return
       sexp_user_exception(ctx, SEXP_FALSE, "couldn't open input file", path);
-  return sexp_make_input_port(ctx, in, sexp_string_data(path));
+  return sexp_make_input_port(ctx, in, path);
 }
 
 static sexp sexp_open_output_file (sexp ctx, sexp path) {
@@ -1815,7 +1822,7 @@ static sexp sexp_open_output_file (sexp ctx, sexp path) {
   if (! out)
     return
       sexp_user_exception(ctx, SEXP_FALSE, "couldn't open output file", path);
-  return sexp_make_input_port(ctx, out, sexp_string_data(path));
+  return sexp_make_input_port(ctx, out, path);
 }
 
 static sexp sexp_close_port (sexp ctx, sexp port) {
@@ -1834,13 +1841,16 @@ static void sexp_warn_undefs (sexp from, sexp to, sexp out) {
 }
 
 sexp sexp_load (sexp ctx, sexp source, sexp env) {
-  sexp tmp, out, res=SEXP_VOID;
+  sexp tmp, out;
   sexp_gc_var(ctx, ctx2, s_ctx2);
   sexp_gc_var(ctx, x, s_x);
   sexp_gc_var(ctx, in, s_in);
+  sexp_gc_var(ctx, res, s_res);
   sexp_gc_preserve(ctx, ctx2, s_ctx2);
   sexp_gc_preserve(ctx, x, s_x);
   sexp_gc_preserve(ctx, in, s_in);
+  sexp_gc_preserve(ctx, res, s_res);
+  res = SEXP_VOID;
   in = sexp_open_input_file(ctx, source);
   out = env_global_ref(env, the_cur_err_symbol, SEXP_FALSE);
   ctx2 = sexp_make_context(ctx, NULL, env);
@@ -2021,11 +2031,11 @@ static sexp sexp_make_standard_env (sexp ctx, sexp version) {
     env_define(ctx, e, sexp_intern(ctx, sexp_opcode_name(op)), op);
   }
   env_define(ctx, e, the_cur_in_symbol,
-             sexp_make_input_port(ctx, stdin, NULL));
+             sexp_make_input_port(ctx, stdin, SEXP_FALSE));
   env_define(ctx, e, the_cur_out_symbol,
-             sexp_make_output_port(ctx, stdout, NULL));
+             sexp_make_output_port(ctx, stdout, SEXP_FALSE));
   env_define(ctx, e, the_cur_err_symbol,
-             sexp_make_output_port(ctx, stderr, NULL));
+             sexp_make_output_port(ctx, stderr, SEXP_FALSE));
   env_define(ctx, e, the_interaction_env_symbol, e);
   sexp_gc_release(ctx, e, s_e);
   return e;
diff --git a/gc.c b/gc.c
index 3f0b0a06..f881ecd6 100644
--- a/gc.c
+++ b/gc.c
@@ -4,11 +4,12 @@
 
 #include "sexp.h"
 
-/* #define SEXP_INITIAL_HEAP_SIZE (2*1024*1024) */
-#define SEXP_INITIAL_HEAP_SIZE 37000
+#define SEXP_INITIAL_HEAP_SIZE (2*1024*1024)
 #define SEXP_MAXIMUM_HEAP_SIZE 0
-#define SEXP_MINIMUM_OBJECT_SIZE (sexp_sizeof(flonum))
-#define SEXP_GROW_HEAP_RATIO 0.8
+#define SEXP_MINIMUM_OBJECT_SIZE (sexp_sizeof(pair))
+#define SEXP_GROW_HEAP_RATIO 0.7
+
+#define sexp_heap_align(n) sexp_align(n, 4)
 
 typedef struct sexp_heap *sexp_heap;
 
@@ -67,7 +68,7 @@ void sexp_mark (sexp x) {
 #if USE_DEBUG_GC
 int stack_references_pointer_p (sexp ctx, sexp x) {
   sexp *p;
-  for (p=&x; p<stack_base; p++)
+  for (p=(&x)+1; p<stack_base; p++)
     if (*p == x)
       return 1;
   return 0;
@@ -76,8 +77,8 @@ int stack_references_pointer_p (sexp ctx, sexp x) {
 #define stack_references_pointer_p(ctx, x) 0
 #endif
 
-sexp sexp_sweep (sexp ctx) {
-  sexp_uint_t freed, max_freed=0, sum_freed=0, size;
+sexp sexp_sweep (sexp ctx, size_t *sum_freed_ptr) {
+  size_t freed, max_freed=0, sum_freed=0, size;
   sexp_heap h = heap;
   sexp p, q, r;
   char *end;
@@ -133,10 +134,11 @@ sexp sexp_sweep (sexp ctx) {
       }
     }
   }
+  sum_freed_ptr[0] = sum_freed;
   return sexp_make_integer(max_freed);
 }
 
-sexp sexp_gc (sexp ctx) {
+sexp sexp_gc (sexp ctx, size_t *sum_freed) {
   sexp res;
   int i;
   sexp_mark(continuation_resumer);
@@ -144,26 +146,28 @@ sexp sexp_gc (sexp ctx) {
   for (i=0; i<SEXP_SYMBOL_TABLE_SIZE; i++)
     sexp_mark(sexp_symbol_table[i]);
   sexp_mark(ctx);
-  res = sexp_sweep(ctx);
+  res = sexp_sweep(ctx, sum_freed);
   return res;
 }
 
 sexp_heap sexp_make_heap (size_t size) {
   sexp free, next;
   sexp_heap h = (sexp_heap) malloc(sizeof(struct sexp_heap) + size);
-  if (h) {
-    h->size = size;
-    h->data = (char*) sexp_heap_align((sexp_uint_t)&(h->data));
-    free = h->free_list = (sexp) h->data;
-    h->next = NULL;
-    next = (sexp) ((char*)free + sexp_heap_align(sexp_sizeof(pair)));
-    sexp_pointer_tag(free) = SEXP_PAIR;
-    sexp_car(free) = 0; /* actually sexp_sizeof(pair) */
-    sexp_cdr(free) = next;
-    sexp_pointer_tag(next) = SEXP_PAIR;
-    sexp_car(next) = (sexp) (size - sexp_heap_align(sexp_sizeof(pair)));
-    sexp_cdr(next) = SEXP_NULL;
+  if (! h) {
+    fprintf(stderr, "out of memory allocating %ld byte heap, aborting\n", size);
+    exit(70);
   }
+  h->size = size;
+  h->data = (char*) sexp_heap_align((sexp_uint_t)&(h->data));
+  free = h->free_list = (sexp) h->data;
+  h->next = NULL;
+  next = (sexp) ((char*)free + sexp_heap_align(sexp_sizeof(pair)));
+  sexp_pointer_tag(free) = SEXP_PAIR;
+  sexp_car(free) = 0; /* actually sexp_sizeof(pair) */
+  sexp_cdr(free) = next;
+  sexp_pointer_tag(next) = SEXP_PAIR;
+  sexp_car(next) = (sexp) (size - sexp_heap_align(sexp_sizeof(pair)));
+  sexp_cdr(next) = SEXP_NULL;
   return h;
 }
 
@@ -205,15 +209,15 @@ void* sexp_try_alloc (sexp ctx, size_t size) {
 
 void* sexp_alloc (sexp ctx, size_t size) {
   void *res;
-  size_t freed;
+  size_t max_freed, sum_freed;
   sexp_heap h;
   size = sexp_heap_align(size);
   res = sexp_try_alloc(ctx, size);
   if (! res) {
-    freed = sexp_unbox_integer(sexp_gc(ctx));
+    max_freed = sexp_unbox_integer(sexp_gc(ctx, &sum_freed));
     h = sexp_heap_last(heap);
-    if (((freed < size)
-         || ((h->size - freed) < h->size*(1 - SEXP_GROW_HEAP_RATIO)))
+    if (((max_freed < size)
+         || ((h->size - sum_freed) < (h->size*(1 - SEXP_GROW_HEAP_RATIO))))
         && ((! SEXP_MAXIMUM_HEAP_SIZE) || (size < SEXP_MAXIMUM_HEAP_SIZE)))
       sexp_grow_heap(ctx, size);
     res = sexp_try_alloc(ctx, size);
diff --git a/sexp.c b/sexp.c
index 69516f5f..ed8071ae 100644
--- a/sexp.c
+++ b/sexp.c
@@ -6,12 +6,12 @@
 
 /* optional huffman-compressed immediate symbols */
 #if USE_HUFF_SYMS
-struct huff_entry {
+struct sexp_huff_entry {
   unsigned char len;
   unsigned short bits;
 };
 #include "opt/sexp-hufftabs.c"
-static struct huff_entry huff_table[] = {
+static struct sexp_huff_entry huff_table[] = {
 #include "opt/sexp-huff.c"
 };
 #endif
@@ -67,8 +67,8 @@ static struct sexp_struct sexp_types[] = {
   _DEF_TYPE(SEXP_VECTOR, sexp_offsetof(vector, data), 0, sexp_offsetof(vector, length), 1, sexp_sizeof(vector), sexp_offsetof(vector, length), 4, "vector"),
   _DEF_TYPE(SEXP_FLONUM, 0, 0, 0, 0, sexp_sizeof(flonum), 0, 0, "flonum"),
   _DEF_TYPE(SEXP_BIGNUM, 0, 0, 0, 0, sexp_sizeof(bignum), sexp_offsetof(bignum, length), 4, "bignum"),
-  _DEF_TYPE(SEXP_IPORT, sexp_offsetof(port, cookie), 1, 0, 0, sexp_sizeof(port), 0, 0, "input-port"),
-  _DEF_TYPE(SEXP_OPORT, sexp_offsetof(port, cookie), 1, 0, 0, sexp_sizeof(port), 0, 0, "output-port"),
+  _DEF_TYPE(SEXP_IPORT, sexp_offsetof(port, name), 2, 0, 0, sexp_sizeof(port), 0, 0, "input-port"),
+  _DEF_TYPE(SEXP_OPORT, sexp_offsetof(port, name), 2, 0, 0, sexp_sizeof(port), 0, 0, "output-port"),
   _DEF_TYPE(SEXP_EXCEPTION, sexp_offsetof(exception, kind), 6, 0, 0, sexp_sizeof(exception), 0, 0, "exception"),
   _DEF_TYPE(SEXP_PROCEDURE, sexp_offsetof(procedure, bc), 2, 0, 0, sexp_sizeof(procedure), 0, 0, "procedure"),
   _DEF_TYPE(SEXP_MACRO, sexp_offsetof(macro, proc), 2, 0, 0, sexp_sizeof(macro), 0, 0, "macro"),
@@ -214,8 +214,7 @@ static sexp sexp_read_error (sexp ctx, char *msg, sexp irritants, sexp port) {
   sexp_gc_var(ctx, str, s_str);
   sexp_gc_preserve(ctx, name, s_name);
   sexp_gc_preserve(ctx, str, s_str);
-  name = (sexp_port_name(port)
-          ? sexp_c_string(ctx, sexp_port_name(port), -1) : SEXP_FALSE);
+  name = (sexp_port_name(port) ? sexp_port_name(port) : SEXP_FALSE);
   str = sexp_c_string(ctx, msg, -1);
   res = sexp_make_exception(ctx, the_read_error_symbol,
                             str, irritants, SEXP_FALSE, name,
@@ -402,7 +401,8 @@ sexp sexp_make_string(sexp ctx, sexp len, sexp ch) {
 sexp sexp_c_string(sexp ctx, char *str, sexp_sint_t slen) {
   sexp_sint_t len = ((slen >= 0) ? slen : strlen(str));
   sexp s = sexp_make_string(ctx, sexp_make_integer(len), SEXP_VOID);
-  memcpy(sexp_string_data(s), str, len+1);
+  memcpy(sexp_string_data(s), str, len);
+  sexp_string_data(s)[len] = '\0';
   return s;
 }
 
@@ -425,7 +425,8 @@ sexp sexp_substring (sexp ctx, sexp str, sexp start, sexp end) {
   res = sexp_make_string(ctx, sexp_fx_sub(end, start), SEXP_VOID);
   memcpy(sexp_string_data(res),
          sexp_string_data(str)+sexp_unbox_integer(start),
-         sexp_string_length(res)+1);
+         sexp_string_length(res));
+  sexp_string_data(res)[sexp_string_length(res)] = '\0';
   return res;
 }
 
@@ -442,7 +443,7 @@ static sexp_uint_t sexp_string_hash(char *str, sexp_uint_t acc) {
 #endif
 
 sexp sexp_intern(sexp ctx, char *str) {
-  struct huff_entry he;
+  struct sexp_huff_entry he;
   sexp_uint_t len, res=FNV_OFFSET_BASIS, space=3, newbits, bucket;
   char c, *p=str;
   sexp ls;
@@ -529,9 +530,10 @@ sexp sexp_vector(sexp ctx, int count, ...) {
 
 #if SEXP_BSD
 
-#define sexp_stream_buf(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(0))
-#define sexp_stream_size(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(1))
-#define sexp_stream_pos(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(2))
+#define sexp_stream_ctx(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(0))
+#define sexp_stream_buf(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(1))
+#define sexp_stream_size(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(2))
+#define sexp_stream_pos(vec) sexp_vector_ref((sexp)vec, sexp_make_integer(3))
 
 int sstream_read (void *vec, char *dst, int n) {
   sexp_uint_t len = sexp_unbox_integer(sexp_stream_size(vec));
@@ -550,7 +552,9 @@ int sstream_write (void *vec, const char *src, int n) {
   pos = sexp_unbox_integer(sexp_stream_pos(vec));
   newpos = pos+n;
   if (newpos >= len) {
-    newbuf = sexp_make_string(NULL, sexp_make_integer(newpos*2), SEXP_VOID);
+    newbuf = sexp_make_string(sexp_stream_ctx(vec),
+                              sexp_make_integer(newpos*2),
+                              SEXP_VOID);
     memcpy(sexp_string_data(newbuf),
            sexp_string_data(sexp_stream_buf(vec)),
            pos);
@@ -580,10 +584,11 @@ sexp sexp_make_input_string_port (sexp ctx, sexp str) {
   sexp res;
   sexp_gc_var(ctx, cookie, s_cookie);
   sexp_gc_preserve(ctx, cookie, s_cookie);
-  cookie = sexp_vector(ctx, 3, str, sexp_make_integer(sexp_string_length(str)),
+  cookie = sexp_vector(ctx, 4, ctx, str,
+                       sexp_make_integer(sexp_string_length(str)),
                        sexp_make_integer(0));
   in = funopen(cookie, &sstream_read, NULL, &sstream_seek, NULL);
-  res = sexp_make_input_port(ctx, in, NULL);
+  res = sexp_make_input_port(ctx, in, SEXP_FALSE);
   sexp_port_cookie(res) = cookie;
   sexp_gc_release(ctx, cookie, s_cookie);
   return res;
@@ -595,10 +600,10 @@ sexp sexp_make_output_string_port (sexp ctx) {
   sexp_gc_var(ctx, cookie, s_cookie);
   sexp_gc_preserve(ctx, cookie, s_cookie);
   size = sexp_make_integer(SEXP_INIT_STRING_PORT_SIZE);
-  cookie = sexp_vector(ctx, 3, sexp_make_string(NULL, size, SEXP_VOID),
+  cookie = sexp_vector(ctx, 4, ctx, sexp_make_string(ctx, size, SEXP_VOID),
                        size, sexp_make_integer(0));
   out = funopen(cookie, NULL, &sstream_write, &sstream_seek, NULL);
-  res = sexp_make_output_port(ctx, out, NULL);
+  res = sexp_make_output_port(ctx, out, SEXP_FALSE);
   sexp_port_cookie(res) = cookie;
   sexp_gc_release(ctx, cookie, s_cookie);
   return res;
@@ -617,14 +622,14 @@ sexp sexp_get_output_string (sexp ctx, sexp port) {
 
 sexp sexp_make_input_string_port (sexp ctx, sexp str) {
   FILE *in = fmemopen(sexp_string_data(str), sexp_string_length(str), "r");
-  return sexp_make_input_port(in, NULL);
+  return sexp_make_input_port(ctx, in, SEXP_FALSE);
 }
 
 sexp sexp_make_output_string_port (sexp ctx) {
   FILE *out;
   sexp buf = sexp_alloc_type(ctx, string, SEXP_STRING), res;
   out = open_memstream(&sexp_string_data(buf), &sexp_string_length(buf));
-  res = sexp_make_input_port(out, NULL);
+  res = sexp_make_input_port(ctx, out, SEXP_FALSE);
   sexp_port_cookie(res) = buf;
   return res;
 }
@@ -641,18 +646,18 @@ sexp sexp_get_output_string (sexp ctx, sexp port) {
 
 #endif
 
-sexp sexp_make_input_port (sexp ctx, FILE* in, char *path) {
+sexp sexp_make_input_port (sexp ctx, FILE* in, sexp name) {
   sexp p = sexp_alloc_type(ctx, port, SEXP_IPORT);
   sexp_port_stream(p) = in;
-  sexp_port_name(p) = path;
+  sexp_port_name(p) = name;
   sexp_port_line(p) = 0;
   return p;
 }
 
-sexp sexp_make_output_port (sexp ctx, FILE* out, char *path) {
+sexp sexp_make_output_port (sexp ctx, FILE* out, sexp name) {
   sexp p = sexp_alloc_type(ctx, port, SEXP_OPORT);
   sexp_port_stream(p) = out;
-  sexp_port_name(p) = path;
+  sexp_port_name(p) = name;
   sexp_port_line(p) = 0;
   return p;
 }
@@ -665,7 +670,7 @@ void sexp_write (sexp obj, sexp out) {
   char *str=NULL;
 
   if (! obj) {
-    sexp_write_string("#<null>", out);
+    sexp_write_string("#<null>", out); /* shouldn't happen */
   } else if (sexp_pointerp(obj)) {
     switch (sexp_pointer_tag(obj)) {
     case SEXP_PAIR:
diff --git a/sexp.h b/sexp.h
index 4e3dd368..94f6c68b 100644
--- a/sexp.h
+++ b/sexp.h
@@ -6,7 +6,6 @@
 #define SEXP_H
 
 #include "config.h"
-#include "defaults.h"
 
 #include <ctype.h>
 #include <stdio.h>
@@ -14,7 +13,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
-#include <sysexits.h>
 #include <sys/types.h>
 #include <math.h>
 
@@ -123,8 +121,8 @@ struct sexp_struct {
     } symbol;
     struct {
       FILE *stream;
-      char *name;
       sexp_uint_t line;
+      sexp name;
       sexp cookie;
     } port;
     struct {
@@ -216,7 +214,7 @@ struct sexp_struct {
 #define sexp_gc_preserve(ctx, x, y)
 #define sexp_gc_release(ctx, x, y)
 
-#include "gc/include/gc.h"
+#include "gc.h"
 #define sexp_alloc(ctx, size)        GC_malloc(size)
 #define sexp_alloc_atomic(ctx, size) GC_malloc_atomic(size)
 #define sexp_realloc(ctx, x, size)   GC_realloc(x, size)
@@ -257,7 +255,6 @@ void *sexp_realloc(sexp ctx, sexp x, size_t size);
 #endif
 
 #define sexp_align(n, bits) (((n)+(1<<(bits))-1)&(((sexp_uint_t)-1)-((1<<(bits))-1)))
-#define sexp_heap_align(n) sexp_align(n, 4)
 
 #define sexp_sizeof(x) (offsetof(struct sexp_struct, value) \
                          + sizeof(((sexp)0)->value.x))
@@ -540,8 +537,8 @@ sexp sexp_read_number(sexp ctx, sexp in, int base);
 sexp sexp_read_raw(sexp ctx, sexp in);
 sexp sexp_read(sexp ctx, sexp in);
 sexp sexp_read_from_string(sexp ctx, char *str);
-sexp sexp_make_input_port(sexp ctx, FILE* in, char *path);
-sexp sexp_make_output_port(sexp ctx, FILE* out, char *path);
+sexp sexp_make_input_port(sexp ctx, FILE* in, sexp name);
+sexp sexp_make_output_port(sexp ctx, FILE* out, sexp name);
 sexp sexp_make_input_string_port(sexp ctx, sexp str);
 sexp sexp_make_output_string_port(sexp ctx);
 sexp sexp_get_output_string(sexp ctx, sexp port);