diff --git a/eval.c b/eval.c
index b91623e5..2b8510f9 100644
--- a/eval.c
+++ b/eval.c
@@ -2298,7 +2298,7 @@ sexp sexp_eval_string (sexp ctx, char *str) {
   return res;
 }
 
-void sexp_scheme_init () {
+void sexp_scheme_init (void) {
   sexp ctx;
   if (! scheme_initialized_p) {
     scheme_initialized_p = 1;
diff --git a/gc.c b/gc.c
index 7b4262de..c7e2e955 100644
--- a/gc.c
+++ b/gc.c
@@ -227,7 +227,7 @@ void* sexp_alloc (sexp ctx, size_t size) {
   return res;
 }
 
-void sexp_gc_init () {
+void sexp_gc_init (void) {
   sexp_uint_t size = sexp_heap_align(SEXP_INITIAL_HEAP_SIZE);
   heap = sexp_make_heap(size);
 #if USE_DEBUG_GC
diff --git a/include/chibi/eval.h b/include/chibi/eval.h
index 5dbc89d2..4184dd61 100644
--- a/include/chibi/eval.h
+++ b/include/chibi/eval.h
@@ -118,7 +118,7 @@ enum opcode_names {
 
 /**************************** prototypes ******************************/
 
-SEXP_API void sexp_scheme_init();
+SEXP_API void sexp_scheme_init(void);
 SEXP_API sexp sexp_apply(sexp context, sexp proc, sexp args);
 SEXP_API sexp sexp_eval(sexp context, sexp obj);
 SEXP_API sexp sexp_eval_string(sexp context, char *str);
diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index 265e17d2..446671ea 100644
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -10,9 +10,11 @@
 
 #include <ctype.h>
 #include <stdio.h>
+
 #ifdef PLAN9
+#include <u.h>
+#include <libc.h>
 typedef unsigned long size_t;
-#define offsetof(st, m) ((size_t) ((char*)&((st*)(0))->m - (char*)0))
 #else
 #include <stddef.h>
 #include <stdlib.h>
@@ -103,7 +105,7 @@ typedef struct sexp_struct *sexp;
 #define SEXP_MIN_FIXNUM (-SEXP_MAX_FIXNUM-1)
 
 /* procedure types */
-typedef sexp (*sexp_proc0) ();
+typedef sexp (*sexp_proc0) (void);
 typedef sexp (*sexp_proc1) (sexp);
 typedef sexp (*sexp_proc2) (sexp, sexp);
 typedef sexp (*sexp_proc3) (sexp, sexp, sexp);
@@ -622,7 +624,7 @@ SEXP_API sexp sexp_user_exception (sexp ctx, sexp self, char *message, sexp obj)
 SEXP_API sexp sexp_type_exception (sexp ctx, char *message, sexp obj);
 SEXP_API sexp sexp_range_exception (sexp ctx, sexp obj, sexp start, sexp end);
 SEXP_API sexp sexp_print_exception(sexp ctx, sexp exn, sexp out);
-SEXP_API void sexp_init();
+SEXP_API void sexp_init(void);
 
 #endif /* ! SEXP_H */
 
diff --git a/mkfile b/mkfile
index 1c6fb068..3aff84cd 100644
--- a/mkfile
+++ b/mkfile
@@ -4,36 +4,22 @@ BIN=/$objtype/bin
 TARG=chibi-scheme
 MODDIR=/sys/lib/chibi-scheme
 
-CPPFLAGS= -Iinclude -DPLAN9 -DUSE_STRING_STREAMS=0 -DUSE_DEBUG=0
-CFLAGS=	-c -B $CPPFLAGS
+CPPFLAGS= -Iinclude -DPLAN9 '-DUSE_STRING_STREAMS=0' '-DUSE_DEBUG=0'
+CFLAGS= -p $CPPFLAGS
 
 OFILES=sexp.$O eval.$O main.$O
-IFILES=${OFILES:%.$O=%.i}
 HFILES=include/chibi/sexp.h include/chibi/eval.h include/chibi/config.h include/chibi/install.h
 
-%.i: %.c $HFILES
-	cpp $CPPFLAGS $stem.c > $target
-
-%.$O: %.i
-	$CC $CFLAGS -c -o $target $prereq
-
-all:V: $TARG
+</sys/src/cmd/mkone
 
 include/chibi/install.h: mkfile
 	echo '#define sexp_module_dir "'$MODDIR'"' > include/chibi/install.h
 
-$TARG: $OFILES
-	$LD $LDFLAGS -o $target $prereq
-
-$BIN/%: %
-	cp $stem $target
-
-clean:V:
-	rm -f $IFILES $TARG *.[$OS]
-
 install:V: $BIN/$TARG
-	mkdir -p $MODDIR
+	test -d $MODDIR || mkdir -p $MODDIR
 	cp init.scm $MODDIR/
 
 test:V:
 	./chibi-scheme tests/r5rs-tests.scm
+
+sexp.c:N:	gc.c opt/bignum.c
diff --git a/opt/bignum.c b/opt/bignum.c
index 245c15e5..e7f9a2f9 100644
--- a/opt/bignum.c
+++ b/opt/bignum.c
@@ -186,12 +186,16 @@ sexp sexp_read_bignum (sexp ctx, sexp in, sexp_uint_t init,
   return sexp_bignum_normalize(res);
 }
 
-#ifdef PLAN9
-#define log2(n) (log(n)/log(2))
-#endif
+static int log2i(int v) {
+  int i;
+  for (i = 0; i < sizeof(v)*8; i++)
+    if ((1<<(i+1)) > v)
+      break;
+  return i;
+}
 
 sexp sexp_write_bignum (sexp ctx, sexp a, sexp out, sexp_uint_t base) {
-  int i, str_len, lg_base = trunc(log2(base));
+  int i, str_len, lg_base = log2i(base);
   char *data;
   sexp_gc_var(ctx, b, s_b);
   sexp_gc_var(ctx, str, s_str);
diff --git a/sexp.c b/sexp.c
index 4c4342a4..093c2d33 100644
--- a/sexp.c
+++ b/sexp.c
@@ -40,11 +40,11 @@ static char sexp_separators[] = {
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, /* x5_ */
 };
 
-static int digit_value (c) {
+static int digit_value (int c) {
   return (((c)<='9') ? ((c) - '0') : ((toupper(c) - 'A') + 10));
 }
 
-static int hex_digit (n) {
+static int hex_digit (int n) {
   return ((n<=9) ? ('0' + n) : ('A' + n - 10));
 }
 
@@ -86,7 +86,7 @@ static struct sexp_struct sexp_type_specs[] = {
   _DEF_TYPE(SEXP_CORE, 0, 0, 0, 0, sexp_sizeof(core), 0, 0, "core-form"),
   _DEF_TYPE(SEXP_OPCODE, sexp_offsetof(opcode, data), 2, 0, 0, sexp_sizeof(opcode), 0, 0, "opcode"),
   _DEF_TYPE(SEXP_LAMBDA, sexp_offsetof(lambda, name), 8, 0, 0, sexp_sizeof(lambda), 0, 0, "lambda"),
-  _DEF_TYPE(SEXP_CND, sexp_offsetof(cnd, test), 3, 0, 0, sexp_sizeof(cnd), 0, 0, "conditoinal"),
+  _DEF_TYPE(SEXP_CND, sexp_offsetof(cnd, test), 3, 0, 0, sexp_sizeof(cnd), 0, 0, "conditional"),
   _DEF_TYPE(SEXP_REF, sexp_offsetof(ref, name), 2, 0, 0, sexp_sizeof(ref), 0, 0, "reference"),
   _DEF_TYPE(SEXP_SET, sexp_offsetof(set, var), 2, 0, 0, sexp_sizeof(set), 0, 0, "set!"),
   _DEF_TYPE(SEXP_SEQ, sexp_offsetof(seq, ls), 1, 0, 0, sexp_sizeof(seq), 0, 0, "sequence"),
@@ -1357,7 +1357,7 @@ sexp sexp_write_to_string(sexp ctx, sexp obj) {
   return str;
 }
 
-void sexp_init() {
+void sexp_init(void) {
   int i;
   sexp ctx;
   if (! sexp_initialized_p) {