diff --git a/lib/chibi/repl.module b/lib/chibi/repl.module
new file mode 100644
index 00000000..4db9a267
--- /dev/null
+++ b/lib/chibi/repl.module
@@ -0,0 +1,5 @@
+
+(define-module (chibi repl)
+  (export repl)
+  (import-immutable (scheme) (chibi process))
+  (include "repl.scm"))
diff --git a/lib/chibi/repl.scm b/lib/chibi/repl.scm
new file mode 100644
index 00000000..307b0253
--- /dev/null
+++ b/lib/chibi/repl.scm
@@ -0,0 +1,58 @@
+
+(define (run-repl module env)
+  (if module (display module))
+  (display "> ")
+  (flush-output)
+  (let lp ()
+    (let ((ch (peek-char)))
+      (cond ((eof-object? ch)
+             (exit 0))
+            ((and (char? ch) (char-whitespace? ch))
+             (read-char)
+             (lp)))))
+  (cond
+   ((eq? #\@ (peek-char))
+    (read-char)
+    (let ((sym (read)))
+      (if (not (symbol? sym))
+          (error "repl: invalid @ syntax: @" sym)
+          (case sym
+            ((config)
+             (let ((res (eval (read) *config-env*)))
+               (cond
+                ((not (eq? res (if #f #f)))
+                 (write res)
+                 (newline)))
+               (run-repl module env)))
+            ((in)
+             (let ((mod (read)))
+               (if (or (not mod) (equal? mod '(scheme)))
+                   (run-repl #f (interaction-environment))
+                   (let ((env (eval `(module-env (load-module ',mod))
+                                    *config-env*)))
+                     (run-repl mod env)))))
+            (else
+             (error "repl: unknown @ escape" sym))))))
+   (else
+    (let ((expr (read)))
+      (cond
+       ((eof-object? expr)
+        (exit 0))
+       (else
+        (let ((res (eval expr env)))
+          (cond
+           ((not (eq? res (if #f #f)))
+            (write res)
+            (newline)))
+          (run-repl module env))))))))
+
+(define (repl)
+  (set-signal-action! signal/interrupt
+                      (lambda (n info)
+                        (newline)
+                        (run-repl #f (interaction-environment))))
+  (current-exception-handler
+   (lambda (exn)
+     (print-exception exn (current-error-port))
+     (run-repl #f (interaction-environment))))
+  (run-repl #f (interaction-environment)))
diff --git a/tools/genstubs.scm b/tools/genstubs.scm
index 114320b4..77f240fb 100755
--- a/tools/genstubs.scm
+++ b/tools/genstubs.scm
@@ -213,7 +213,7 @@
   (memq type '(signed-char short int long boolean)))
 
 (define (unsigned-int-type? type)
-  (memq type '(unsigned-char unsigned-short unsigned-int unsigned-long
+  (memq type '(unsigned-char unsigned-short unsigned unsigned-int unsigned-long
                size_t off_t time_t clock_t dev_t ino_t mode_t nlink_t
                uid_t gid_t pid_t blksize_t blkcnt_t sigval_t)))
 
@@ -425,6 +425,11 @@
    (lambda (expr rename compare)
      `(define-struct-like ,(cadr expr) type: class ,@(cddr expr)))))
 
+(define-syntax define-c-union
+  (er-macro-transformer
+   (lambda (expr rename compare)
+     `(define-struct-like ,(cadr expr) type: union ,@(cddr expr)))))
+
 (define-syntax define-c-type
   (er-macro-transformer
    (lambda (expr rename compare)
@@ -439,8 +444,9 @@
 (define-syntax define-c-const
   (er-macro-transformer
    (lambda (expr rename compare)
-     (set! *consts*
-           (cons (cons (parse-type (cadr expr)) (cddr expr)) *consts*)))))
+     (let ((type (parse-type (cadr expr))))
+       (for-each (lambda (x) (set! *consts* (cons (list type x) *consts*)))
+                 (cddr expr))))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; C code generation
@@ -568,7 +574,7 @@
      (if (type-const? type) "const " "")
      (if struct-type (string-append (symbol->string struct-type) " ") "")
      (string-replace (base-type-c-name base) #\- " ")
-     (if type-spec "*" "")
+     (if struct-type "*" "")
      (if (type-pointer? type) "*" ""))))
 
 (define (check-type arg type)
@@ -605,6 +611,7 @@
      ((eq? base 'port) "SEXP_IPORT")
      ((eq? base 'input-port) "SEXP_IPORT")
      ((eq? base 'output-port) "SEXP_OPORT")
+     ((void-pointer-type? type) "SEXP_CPOINTER")
      (else (type-id-name base)))))
 
 (define (write-validator arg type)
@@ -1112,9 +1119,9 @@
        "  return SEXP_VOID;\n"
        "}\n\n"))
 
-(define (write-type-funcs type)
-  (let ((name (car type))
-        (type (cdr type)))
+(define (write-type-funcs orig-type)
+  (let ((name (car orig-type))
+        (type (cdr orig-type)))
     ;; maybe write finalizer
     (cond
      ((memq 'finalizer: type)
@@ -1139,7 +1146,7 @@
                              (cat ", sexp arg" i)
                              (lp (cdr ls) (+ i 1))))))
                   ") {\n"
-                  "  struct " (type-name name) " *r;\n"
+                  "  " (or (type-struct-type name) "") " " (type-name name) " *r;\n"
                   "  sexp_gc_var1(res);\n"
                   "  sexp_gc_preserve1(ctx, res);\n"
                   ;; "  res = sexp_alloc_tagged(ctx, sexp_sizeof(cpointer) + sizeof(struct " (type-name name) "), "
@@ -1149,8 +1156,8 @@
                   "  res = sexp_alloc_tagged(ctx, sexp_sizeof(cpointer), "
                   (type-id-name name)
                   ");\n"
-                  "  r = sexp_cpointer_value(res) = malloc(sizeof(struct "
-                  (type-name name) "));\n"
+                  "  r = sexp_cpointer_value(res) = malloc(sizeof("
+                  (or (type-struct-type name) "") " " (type-name name) "));\n"
                   "  sexp_freep(res) = 1;\n"
                   (lambda ()
                     (let lp ((ls args) (i 0))