diff --git a/Makefile b/Makefile
index 9b7b6efd..8b85cd0b 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 
 all: chibi-scheme
 
-CFLAGS=-g -fno-inline -save-temps -Os
+CFLAGS=-Wall -g -fno-inline -save-temps -Os
 
 GC_OBJ=./gc/gc.a
 
diff --git a/debug.c b/debug.c
index 7526fa13..6e96b5b5 100644
--- a/debug.c
+++ b/debug.c
@@ -31,7 +31,7 @@ void disasm (sexp bc) {
   case OP_STACK_SET:
   case OP_CLOSURE_REF:
   case OP_PARAMETER:
-    fprintf(stderr, "%d", (long) ((sexp*)ip)[0]);
+    fprintf(stderr, "%ld", (long) ((sexp*)ip)[0]);
     ip += sizeof(sexp);
     break;
   case OP_GLOBAL_REF:
@@ -62,7 +62,7 @@ void disasm (sexp bc) {
 void print_bytecode (sexp bc) {
   int i;
   unsigned char *data = sexp_bytecode_data(bc);
-  fprintf(stderr, "bytecode @ %p, data @ %p, length = %d\n",
+  fprintf(stderr, "bytecode @ %p, data @ %p, length = %lu\n",
           bc, data, sexp_bytecode_length(bc));
   for (i=0; i+16 < sexp_bytecode_length(bc); i+=8) {
     fprintf(stderr, "%02x: %02x %02x %02x %02x %02x %02x %02x %02x   ", i,
diff --git a/eval.c b/eval.c
index ff409d12..cc1d6d40 100644
--- a/eval.c
+++ b/eval.c
@@ -176,8 +176,8 @@ sexp sexp_expand_macro (sexp mac, sexp form, sexp e) {
 
 void analyze(sexp obj, sexp *bc, sexp_uint_t *i, sexp e,
              sexp params, sexp fv, sexp sv, sexp_uint_t *d, int tailp) {
-  int tmp1, tmp2, tmp3;
-  sexp o1, o2, e2, cell;
+  int tmp1, tmp2;
+  sexp o1, o2, e2;
 
  loop:
   if (sexp_pairp(obj)) {
@@ -269,7 +269,7 @@ void analyze(sexp obj, sexp *bc, sexp_uint_t *i, sexp e,
           (*d)++;
           break;
         default:
-          errx(1, "unknown core form: %s", sexp_core_code(o1));
+          errx(1, "unknown core form: %d", sexp_core_code(o1));
         }
       } else if (sexp_opcodep(o1)) {
         analyze_opcode(o1, obj, bc, i, e, params, fv, sv, d, tailp);
@@ -305,14 +305,14 @@ void analyze(sexp obj, sexp *bc, sexp_uint_t *i, sexp e,
         emit(bc, i, OP_STACK_SET);
         emit_word(bc, i, tmp1+1);
         (*d) -= (tmp1-1);
-        for (tmp1; tmp1>0; tmp1--)
+        for ( ; tmp1>0; tmp1--)
           emit(bc, i, OP_DROP);
       } else
 #endif
         /* computed application */
         analyze_app(obj, bc, i, e, params, fv, sv, d, tailp);
     } else {
-      errx(1, "invalid operator: %s", sexp_car(obj));
+      errx(1, "invalid operator: %p", sexp_car(obj));
     }
   } else if (sexp_symbolp(obj)) {
     analyze_var_ref(obj, bc, i, e, params, fv, sv, d);
@@ -398,7 +398,7 @@ void analyze_var_ref (sexp obj, sexp *bc, sexp_uint_t *i, sexp e,
     o1 = env_cell(e, obj);
     fprintf(stderr, "compiling local ref: ");
     sexp_write(obj, cur_error_port);
-    fprintf(stderr, " => %d\n", *d - sexp_unbox_integer(sexp_cdr(o1)));
+    fprintf(stderr, " => %lu\n", *d - sexp_unbox_integer(sexp_cdr(o1)));
     emit(bc, i, OP_STACK_REF);
     emit_word(bc, i, *d - sexp_unbox_integer(sexp_cdr(o1)));
   } else if ((tmp = sexp_list_index(fv, obj)) >= 0) {
@@ -563,7 +563,7 @@ sexp make_opcode_procedure(sexp op, sexp_uint_t i, sexp e) {
 }
 
 sexp compile(sexp params, sexp obj, sexp e, sexp fv, sexp sv, int done_p) {
-  sexp_uint_t i = 0, j, d = 0, core, define_ok=1;
+  sexp_uint_t i=0, j=0, d=0, define_ok=1, core;
   sexp bc = (sexp) SEXP_ALLOC(sexp_sizeof(bytecode)+INIT_BCODE_SIZE);
   sexp sv2 = set_vars(e, params, obj, SEXP_NULL), internals=SEXP_NULL, ls;
   bc->tag = SEXP_BYTECODE;
@@ -631,7 +631,7 @@ sexp compile(sexp params, sexp obj, sexp e, sexp fv, sexp sv, int done_p) {
   if (sexp_pairp(internals)) {
     emit(&bc, &i, OP_STACK_SET);
     emit_word(&bc, &i, j+1);
-    for (j; j>0; j--)
+    for ( ; j>0; j--)
       emit(&bc, &i, OP_DROP);
   }
   emit(&bc, &i, done_p ? OP_DONE : OP_RET);
@@ -864,7 +864,7 @@ sexp vm(sexp bc, sexp e, sexp* stack, sexp_sint_t top) {
     goto make_call;
   case OP_CALL:
     if (top >= INIT_STACK_SIZE)
-      errx(1, "out of stack space: %d", top);
+      errx(1, "out of stack space: %ld", top);
     i = sexp_unbox_integer(((sexp*)ip)[0]);
     tmp1 = stack[top-1];
   make_call:
@@ -880,7 +880,7 @@ sexp vm(sexp bc, sexp e, sexp* stack, sexp_sint_t top) {
     }
     j = i - sexp_unbox_integer(sexp_procedure_num_args(tmp1));
     if (j < 0) {
-      fprintf(stderr, "error: expected %d args but got %d\n",
+      fprintf(stderr, "error: expected %ld args but got %ld\n",
               sexp_unbox_integer(sexp_procedure_num_args(tmp1)),
               i);
       sexp_raise(sexp_intern("not-enough-args"));
@@ -895,7 +895,7 @@ sexp vm(sexp bc, sexp e, sexp* stack, sexp_sint_t top) {
         top -= (j-1);
         i-=(j-1);
       } else {
-        fprintf(stderr, "got: %d, expected: %d\n", i, sexp_procedure_num_args(tmp1));
+        fprintf(stderr, "got: %ld, expected: %d\n", i, sexp_procedure_num_args(tmp1));
         sexp_raise(sexp_intern("too-many-args"));
       }
     } else if (sexp_procedure_variadic_p(tmp1)) {
@@ -1058,7 +1058,7 @@ sexp vm(sexp bc, sexp e, sexp* stack, sexp_sint_t top) {
 /*     fprintf(stderr, "... done returning\n"); */
     break;
   case OP_DONE:
-    fprintf(stderr, "finally returning @ %d: ", top-1);
+    fprintf(stderr, "finally returning @ %ld: ", top-1);
     fflush(stderr);
     sexp_write(stack[top-1], cur_error_port);
     fprintf(stderr, "\n");
@@ -1252,7 +1252,7 @@ void repl (sexp e, sexp *stack) {
 }
 
 int main (int argc, char **argv) {
-  sexp bc, e, obj, res, in, out, *stack, err_handler, err_handler_sym;
+  sexp bc, e, obj, res, *stack, err_handler, err_handler_sym;
   sexp_uint_t i, quit=0, init_loaded=0;
 
   scheme_init();
diff --git a/sexp.c b/sexp.c
index 745f3e87..64ac1bf6 100644
--- a/sexp.c
+++ b/sexp.c
@@ -203,8 +203,8 @@ sexp sexp_intern(char *str) {
 
 #if USE_HUFF_SYMS
   res = 0;
-  for (p=str; c=*p; p++) {
-    he = huff_table[c];
+  for ( ; (c=*p); p++) {
+    he = huff_table[(unsigned char)c];
     newbits = he.len;
     if ((space+newbits) > (sizeof(sexp)*8)) {
       goto normal_intern;
@@ -322,6 +322,7 @@ off_t sstream_seek(void *vec, off_t offset, int whence) {
 
 int sstream_close(void *vec) {
   sexp_free((sexp)vec);
+  return 0;
 }
 
 sexp sexp_make_input_port(FILE* in) {
@@ -355,9 +356,9 @@ sexp sexp_get_output_string(sexp port) {
 
 void sexp_write (sexp obj, sexp out) {
   unsigned long len, c, res;
-  long i;
+  long i=0;
   sexp x, *elts;
-  char *str;
+  char *str=NULL;
 
   if (! obj) {
     sexp_write_string("#<null>", out);
@@ -429,13 +430,12 @@ void sexp_write (sexp obj, sexp out) {
       break;
     }
   } else if (sexp_integerp(obj)) {
-    sexp_printf(out, "%d", sexp_unbox_integer(obj));
+    sexp_printf(out, "%ld", sexp_unbox_integer(obj));
   } else if (sexp_charp(obj)) {
-      if (33 <= sexp_unbox_character(obj) < 127) {
-        sexp_printf(out, "#\\%c", sexp_unbox_character(obj));
-      } else {
-        sexp_printf(out, "#\\x%02d", sexp_unbox_character(obj));
-      }
+    if ((33 <= sexp_unbox_character(obj)) && (sexp_unbox_character(obj) < 127))
+      sexp_printf(out, "#\\%c", sexp_unbox_character(obj));
+    else
+      sexp_printf(out, "#\\x%02d", sexp_unbox_character(obj));
   } else if (sexp_symbolp(obj)) {
 
 #if USE_HUFF_SYMS
diff --git a/sexp.h b/sexp.h
index f0d90bc0..d03aa309 100644
--- a/sexp.h
+++ b/sexp.h
@@ -194,10 +194,10 @@ struct sexp_struct {
 #define SEXP_DOTP(x) ((x)==sexp_the_dot_symbol)
 #endif
 
-#define sexp_make_integer(n)    ((sexp) (((sexp_sint_t) n<<SEXP_FIXNUM_BITS) + SEXP_FIXNUM_TAG))
-#define sexp_unbox_integer(n)   ((sexp_sint_t) n>>SEXP_FIXNUM_BITS)
-#define sexp_make_character(n)  ((sexp) (((sexp_sint_t) n<<SEXP_EXTENDED_BITS) + SEXP_CHAR_TAG))
-#define sexp_unbox_character(n) ((sexp_sint_t) n>>SEXP_EXTENDED_BITS)
+#define sexp_make_integer(n)    ((sexp) ((((sexp_sint_t)n)<<SEXP_FIXNUM_BITS) + SEXP_FIXNUM_TAG))
+#define sexp_unbox_integer(n)   (((sexp_sint_t)n)>>SEXP_FIXNUM_BITS)
+#define sexp_make_character(n)  ((sexp) ((((sexp_sint_t)n)<<SEXP_EXTENDED_BITS) + SEXP_CHAR_TAG))
+#define sexp_unbox_character(n) ((int) (((sexp_sint_t)n)>>SEXP_EXTENDED_BITS))
 
 #define sexp_flonum_value(f) ((f)->value.flonum)