diff --git a/py/bc.c b/py/bc.c
index e9cba3823d..91ef9c070f 100644
--- a/py/bc.c
+++ b/py/bc.c
@@ -75,9 +75,9 @@ STATIC NORETURN void fun_pos_args_mismatch(mp_obj_fun_bc_t *f, mp_uint_t expecte
 }
 
 #if DEBUG_PRINT
-STATIC void dump_args(const mp_obj_t *a, int sz) {
+STATIC void dump_args(const mp_obj_t *a, mp_uint_t sz) {
     DEBUG_printf("%p: ", a);
-    for (int i = 0; i < sz; i++) {
+    for (mp_uint_t i = 0; i < sz; i++) {
         DEBUG_printf("%p ", a[i]);
     }
     DEBUG_printf("\n");
@@ -179,7 +179,7 @@ continue2:;
         // fill in defaults for positional args
         mp_obj_t *d = &code_state->state[n_state - self->n_pos_args];
         mp_obj_t *s = &self->extra_args[self->n_def_args - 1];
-        for (int i = self->n_def_args; i > 0; i--, d++, s--) {
+        for (mp_uint_t i = self->n_def_args; i > 0; i--, d++, s--) {
             if (*d == MP_OBJ_NULL) {
                 *d = *s;
             }
diff --git a/py/bc.h b/py/bc.h
index b92342d84d..08f4ef0d4f 100644
--- a/py/bc.h
+++ b/py/bc.h
@@ -53,8 +53,8 @@ mp_uint_t mp_decode_uint(const byte **ptr);
 
 mp_vm_return_kind_t mp_execute_bytecode(mp_code_state *code_state, volatile mp_obj_t inject_exc);
 void mp_setup_code_state(mp_code_state *code_state, mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args);
-void mp_bytecode_print(const void *descr, const byte *code, int len);
-void mp_bytecode_print2(const byte *code, int len);
+void mp_bytecode_print(const void *descr, const byte *code, mp_uint_t len);
+void mp_bytecode_print2(const byte *code, mp_uint_t len);
 
 // Helper macros to access pointer with least significant bit holding a flag
 #define MP_TAGPTR_PTR(x) ((void*)((mp_uint_t)(x) & ~((mp_uint_t)1)))
diff --git a/py/binary.c b/py/binary.c
index 835ba8aa20..1201ec34fa 100644
--- a/py/binary.c
+++ b/py/binary.c
@@ -99,7 +99,7 @@ int mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign) {
     return size;
 }
 
-mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index) {
+mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index) {
     mp_int_t val = 0;
     switch (typecode) {
         case 'b':
@@ -250,7 +250,7 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **
     mp_binary_set_int(MIN(size, sizeof(val)), struct_type == '>', p, in);
 }
 
-void mp_binary_set_val_array(char typecode, void *p, int index, mp_obj_t val_in) {
+void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t val_in) {
     switch (typecode) {
 #if MICROPY_PY_BUILTINS_FLOAT
         case 'f':
@@ -265,7 +265,7 @@ void mp_binary_set_val_array(char typecode, void *p, int index, mp_obj_t val_in)
     }
 }
 
-void mp_binary_set_val_array_from_int(char typecode, void *p, int index, mp_int_t val) {
+void mp_binary_set_val_array_from_int(char typecode, void *p, mp_uint_t index, mp_int_t val) {
     switch (typecode) {
         case 'b':
             ((int8_t*)p)[index] = val;
diff --git a/py/binary.h b/py/binary.h
index 5f577da020..2a63ba9928 100644
--- a/py/binary.h
+++ b/py/binary.h
@@ -29,9 +29,9 @@
 #define BYTEARRAY_TYPECODE 0
 
 int mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign);
-mp_obj_t mp_binary_get_val_array(char typecode, void *p, int index);
-void mp_binary_set_val_array(char typecode, void *p, int index, mp_obj_t val_in);
-void mp_binary_set_val_array_from_int(char typecode, void *p, int index, mp_int_t val);
+mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index);
+void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t val_in);
+void mp_binary_set_val_array_from_int(char typecode, void *p, mp_uint_t index, mp_int_t val);
 mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte **ptr);
 void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **ptr);
 long long mp_binary_get_int(mp_uint_t size, bool is_signed, bool big_endian, byte *p);
diff --git a/py/builtin.c b/py/builtin.c
index 471e294ccb..1af92a448f 100644
--- a/py/builtin.c
+++ b/py/builtin.c
@@ -415,9 +415,9 @@ STATIC mp_obj_t mp_builtin_print(mp_uint_t n_args, const mp_obj_t *args, mp_map_
 
     pfenv_t pfenv;
     pfenv.data = stream_obj;
-    pfenv.print_strn = (void (*)(void *, const char *, unsigned int))mp_stream_write;
+    pfenv.print_strn = (void (*)(void *, const char *, mp_uint_t))mp_stream_write;
     #endif
-    for (int i = 0; i < n_args; i++) {
+    for (mp_uint_t i = 0; i < n_args; i++) {
         if (i > 0) {
             #if MICROPY_PY_IO
             mp_stream_write(stream_obj, sep_data, sep_len);
diff --git a/py/builtinimport.c b/py/builtinimport.c
index 07b7c199ae..7270e1f840 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -82,7 +82,7 @@ STATIC mp_import_stat_t find_file(const char *file_str, uint file_len, vstr_t *d
         return stat_dir_or_file(dest);
     } else {
         // go through each path looking for a directory or file
-        for (int i = 0; i < path_num; i++) {
+        for (mp_uint_t i = 0; i < path_num; i++) {
             vstr_reset(dest);
             mp_uint_t p_len;
             const char *p = mp_obj_str_get_data(path_items[i], &p_len);
@@ -167,7 +167,7 @@ STATIC void do_load(mp_obj_t module_obj, vstr_t *file) {
 mp_obj_t mp_builtin___import__(mp_uint_t n_args, mp_obj_t *args) {
 #if DEBUG_PRINT
     DEBUG_printf("__import__:\n");
-    for (int i = 0; i < n_args; i++) {
+    for (mp_uint_t i = 0; i < n_args; i++) {
         DEBUG_printf("  ");
         mp_obj_print(args[i], PRINT_REPR);
         DEBUG_printf("\n");
@@ -176,7 +176,7 @@ mp_obj_t mp_builtin___import__(mp_uint_t n_args, mp_obj_t *args) {
 
     mp_obj_t module_name = args[0];
     mp_obj_t fromtuple = mp_const_none;
-    int level = 0;
+    mp_int_t level = 0;
     if (n_args >= 4) {
         fromtuple = args[3];
         if (n_args >= 5) {
diff --git a/py/compile.c b/py/compile.c
index a9d19d2a94..4ccd405c79 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -493,7 +493,7 @@ STATIC void cpython_c_tuple_emit_const(compiler_t *comp, mp_parse_node_t pn, vst
         return;
     }
 
-    int arg = MP_PARSE_NODE_LEAF_ARG(pn);
+    mp_uint_t arg = MP_PARSE_NODE_LEAF_ARG(pn);
     switch (MP_PARSE_NODE_LEAF_KIND(pn)) {
         case MP_PARSE_NODE_ID: assert(0);
         case MP_PARSE_NODE_INTEGER: vstr_printf(vstr, "%s", qstr_str(arg)); break;
@@ -853,7 +853,7 @@ STATIC void c_assign(compiler_t *comp, mp_parse_node_t pn, assign_kind_t assign_
         assert(0);
     } else if (MP_PARSE_NODE_IS_LEAF(pn)) {
         if (MP_PARSE_NODE_IS_ID(pn)) {
-            int arg = MP_PARSE_NODE_LEAF_ARG(pn);
+            qstr arg = MP_PARSE_NODE_LEAF_ARG(pn);
             switch (assign_kind) {
                 case ASSIGN_STORE:
                 case ASSIGN_AUG_STORE:
diff --git a/py/modstruct.c b/py/modstruct.c
index 8d44006381..8122a96685 100644
--- a/py/modstruct.c
+++ b/py/modstruct.c
@@ -164,7 +164,7 @@ STATIC mp_obj_t struct_pack(uint n_args, mp_obj_t *args) {
     // TODO: "The arguments must match the values required by the format exactly."
     const char *fmt = mp_obj_str_get_str(args[0]);
     char fmt_type = get_fmt_type(&fmt);
-    int size = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
+    mp_int_t size = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
     byte *p;
     mp_obj_t res = mp_obj_str_builder_start(&mp_type_bytes, size, &p);
     memset(p, 0, size);
diff --git a/py/mpz.c b/py/mpz.c
index 0599656ea5..b5cc7d1838 100644
--- a/py/mpz.c
+++ b/py/mpz.c
@@ -58,7 +58,7 @@
    returns sign(i - j)
    assumes i, j are normalised
 */
-STATIC mp_int_t mpn_cmp(const mpz_dig_t *idig, mp_uint_t ilen, const mpz_dig_t *jdig, mp_uint_t jlen) {
+STATIC int mpn_cmp(const mpz_dig_t *idig, mp_uint_t ilen, const mpz_dig_t *jdig, mp_uint_t jlen) {
     if (ilen < jlen) { return -1; }
     if (ilen > jlen) { return 1; }
 
@@ -361,7 +361,7 @@ STATIC void mpn_div(mpz_dig_t *num_dig, mp_uint_t *num_len, mpz_dig_t *den_dig,
 
     // handle simple cases
     {
-        mp_int_t cmp = mpn_cmp(num_dig, *num_len, den_dig, den_len);
+        int cmp = mpn_cmp(num_dig, *num_len, den_dig, den_len);
         if (cmp == 0) {
             *num_len = 0;
             quo_dig[0] = 1;
@@ -744,8 +744,8 @@ bool mpz_is_even(const mpz_t *z) {
     return z->len == 0 || (z->dig[0] & 1) == 0;
 }
 
-mp_int_t mpz_cmp(const mpz_t *z1, const mpz_t *z2) {
-    mp_int_t cmp = z2->neg - z1->neg;
+int mpz_cmp(const mpz_t *z1, const mpz_t *z2) {
+    int cmp = (int)z2->neg - (int)z1->neg;
     if (cmp != 0) {
         return cmp;
     }
diff --git a/py/mpz.h b/py/mpz.h
index a2d8923b91..9dbbbc373a 100644
--- a/py/mpz.h
+++ b/py/mpz.h
@@ -88,7 +88,7 @@ bool mpz_is_neg(const mpz_t *z);
 bool mpz_is_odd(const mpz_t *z);
 bool mpz_is_even(const mpz_t *z);
 
-mp_int_t mpz_cmp(const mpz_t *lhs, const mpz_t *rhs);
+int mpz_cmp(const mpz_t *lhs, const mpz_t *rhs);
 
 mpz_t *mpz_abs(const mpz_t *z);
 mpz_t *mpz_neg(const mpz_t *z);
diff --git a/py/obj.h b/py/obj.h
index 0156286818..7d714a3cdf 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -212,9 +212,9 @@ typedef struct _mp_buffer_info_t {
     // them with ver = sizeof(struct). Cons: overkill for *micro*?
     //int ver; // ?
 
-    void *buf;    // can be NULL if len == 0
-    mp_int_t len; // in bytes; TODO should it be mp_uint_t?
-    int typecode; // as per binary.h; TODO what is the correct type to use?
+    void *buf;      // can be NULL if len == 0
+    mp_uint_t len;  // in bytes
+    int typecode;   // as per binary.h
 
     // Rationale: to load arbitrary-sized sprites directly to LCD
     // Cons: a bit adhoc usecase
diff --git a/py/objarray.c b/py/objarray.c
index 654c38ff33..333ab47e4c 100644
--- a/py/objarray.c
+++ b/py/objarray.c
@@ -66,7 +66,7 @@ STATIC void array_print(void (*print)(void *env, const char *fmt, ...), void *en
         print(env, "array('%c'", o->typecode);
         if (o->len > 0) {
             print(env, ", [");
-            for (int i = 0; i < o->len; i++) {
+            for (mp_uint_t i = 0; i < o->len; i++) {
                 if (i > 0) {
                     print(env, ", ");
                 }
@@ -92,7 +92,7 @@ STATIC mp_obj_t array_construct(char typecode, mp_obj_t initializer) {
 
     mp_obj_t iterable = mp_getiter(initializer);
     mp_obj_t item;
-    int i = 0;
+    mp_uint_t i = 0;
     while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
         if (len == 0) {
             array_append(array, item);
@@ -210,7 +210,7 @@ STATIC mp_obj_t array_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t value
             return res;
 #endif
         } else {
-            uint index = mp_get_index(o->base.type, o->len, index_in, false);
+            mp_uint_t index = mp_get_index(o->base.type, o->len, index_in, false);
             if (value == MP_OBJ_SENTINEL) {
                 // load
                 return mp_binary_get_val_array(o->typecode, o->items, index);
diff --git a/py/objint.c b/py/objint.c
index 240be32833..e0fa7d661a 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -88,8 +88,8 @@ void mp_obj_int_print(void (*print)(void *env, const char *fmt, ...), void *env,
     // enough, a dynamic one will be allocated.
     char stack_buf[sizeof(mp_int_t) * 4];
     char *buf = stack_buf;
-    int buf_size = sizeof(stack_buf);
-    int fmt_size;
+    mp_uint_t buf_size = sizeof(stack_buf);
+    mp_uint_t fmt_size;
 
     char *str = mp_obj_int_formatted(&buf, &buf_size, &fmt_size, self_in, 10, NULL, '\0', '\0');
     print(env, "%s", str);
@@ -135,7 +135,7 @@ STATIC uint int_as_str_size_formatted(uint base, const char *prefix, char comma)
 //
 // The resulting formatted string will be returned from this function and the
 // formatted size will be in *fmt_size.
-char *mp_obj_int_formatted(char **buf, int *buf_size, int *fmt_size, mp_const_obj_t self_in,
+char *mp_obj_int_formatted(char **buf, mp_uint_t *buf_size, mp_uint_t *fmt_size, mp_const_obj_t self_in,
                            int base, const char *prefix, char base_char, char comma) {
     fmt_int_t num;
     if (MP_OBJ_IS_SMALL_INT(self_in)) {
diff --git a/py/objint.h b/py/objint.h
index 638742a850..70d182ba7d 100644
--- a/py/objint.h
+++ b/py/objint.h
@@ -36,9 +36,9 @@ typedef struct _mp_obj_int_t {
 extern const mp_obj_int_t mp_maxsize_obj;
 
 void mp_obj_int_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind);
-char *mp_obj_int_formatted(char **buf, int *buf_size, int *fmt_size, mp_const_obj_t self_in,
+char *mp_obj_int_formatted(char **buf, mp_uint_t *buf_size, mp_uint_t *fmt_size, mp_const_obj_t self_in,
                            int base, const char *prefix, char base_char, char comma);
-char *mp_obj_int_formatted_impl(char **buf, int *buf_size, int *fmt_size, mp_const_obj_t self_in,
+char *mp_obj_int_formatted_impl(char **buf, mp_uint_t *buf_size, mp_uint_t *fmt_size, mp_const_obj_t self_in,
                                 int base, const char *prefix, char base_char, char comma);
 mp_int_t mp_obj_int_hash(mp_obj_t self_in);
 bool mp_obj_int_is_positive(mp_obj_t self_in);
diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index 39806bb277..b75cc8c0bc 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -81,12 +81,12 @@ STATIC mp_obj_int_t *mp_obj_int_new_mpz(void) {
 // formatted size will be in *fmt_size.
 //
 // This particular routine should only be called for the mpz representation of the int.
-char *mp_obj_int_formatted_impl(char **buf, int *buf_size, int *fmt_size, mp_const_obj_t self_in,
+char *mp_obj_int_formatted_impl(char **buf, mp_uint_t *buf_size, mp_uint_t *fmt_size, mp_const_obj_t self_in,
                                 int base, const char *prefix, char base_char, char comma) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_int));
     const mp_obj_int_t *self = self_in;
 
-    uint needed_size = mpz_as_str_size(&self->mpz, base, prefix, comma);
+    mp_uint_t needed_size = mpz_as_str_size(&self->mpz, base, prefix, comma);
     if (needed_size > *buf_size) {
         *buf = m_new(char, needed_size);
         *buf_size = needed_size;
diff --git a/py/objlist.c b/py/objlist.c
index 789a1600d3..1531b6be95 100644
--- a/py/objlist.c
+++ b/py/objlist.c
@@ -164,7 +164,7 @@ STATIC mp_obj_t list_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
                 assert(0);
             }
 
-            int len_adj = slice.start - slice.stop;
+            mp_int_t len_adj = slice.start - slice.stop;
             //printf("Len adj: %d\n", len_adj);
             assert(len_adj <= 0);
             mp_seq_replace_slice_no_grow(self->items, self->len, slice.start, slice.stop, self->items/*NULL*/, 0, mp_obj_t);
@@ -203,7 +203,7 @@ STATIC mp_obj_t list_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
             if (!mp_seq_get_fast_slice_indexes(self->len, index, &slice_out)) {
                 assert(0);
             }
-            int len_adj = slice->len - (slice_out.stop - slice_out.start);
+            mp_int_t len_adj = slice->len - (slice_out.stop - slice_out.start);
             //printf("Len adj: %d\n", len_adj);
             if (len_adj > 0) {
                 if (self->len + len_adj > self->alloc) {
diff --git a/py/objnamedtuple.c b/py/objnamedtuple.c
index 1a8b328be5..018c8bbebd 100644
--- a/py/objnamedtuple.c
+++ b/py/objnamedtuple.c
@@ -81,7 +81,7 @@ STATIC uint namedtuple_count_fields(const char *namedef) {
 
 STATIC int namedtuple_find_field(const char *name, const char *namedef) {
     int id = 0;
-    int len = strlen(name);
+    size_t len = strlen(name);
     while (namedef) {
         if (memcmp(name, namedef, len) == 0) {
             namedef += len;
@@ -101,9 +101,9 @@ STATIC void namedtuple_print(void (*print)(void *env, const char *fmt, ...), voi
     print(env, "%s(", qstr_str(o->tuple.base.type->name));
     const char *fields = ((mp_obj_namedtuple_type_t*)o->tuple.base.type)->fields;
 
-    for (int i = 0; i < o->tuple.len; i++) {
+    for (mp_uint_t i = 0; i < o->tuple.len; i++) {
         if (i > 0) {
-                print(env, ", ");
+            print(env, ", ");
         }
         const char *next = fields;
 
diff --git a/py/objrange.c b/py/objrange.c
index dc3662b103..702413f2a9 100644
--- a/py/objrange.c
+++ b/py/objrange.c
@@ -63,7 +63,7 @@ STATIC const mp_obj_type_t range_it_type = {
     .iternext = range_it_iternext,
 };
 
-mp_obj_t mp_obj_new_range_iterator(int cur, int stop, int step) {
+STATIC mp_obj_t mp_obj_new_range_iterator(mp_int_t cur, mp_int_t stop, mp_int_t step) {
     mp_obj_range_it_t *o = m_new_obj(mp_obj_range_it_t);
     o->base.type = &range_it_type;
     o->cur = cur;
diff --git a/py/parse.h b/py/parse.h
index f8c1d5718b..45645951af 100644
--- a/py/parse.h
+++ b/py/parse.h
@@ -68,7 +68,6 @@ typedef struct _mp_parse_node_struct_t {
 #define MP_PARSE_NODE_IS_TOKEN_KIND(pn, k) ((pn) == (MP_PARSE_NODE_TOKEN | ((k) << 5)))
 
 #define MP_PARSE_NODE_LEAF_KIND(pn) ((pn) & 0x1f)
-// TODO should probably have int and uint versions of this macro
 #define MP_PARSE_NODE_LEAF_ARG(pn) (((mp_uint_t)(pn)) >> 5)
 #define MP_PARSE_NODE_LEAF_SMALL_INT(pn) (((mp_int_t)(pn)) >> 1)
 #define MP_PARSE_NODE_STRUCT_KIND(pns) ((pns)->kind_num_nodes & 0xff)
diff --git a/py/pfenv.c b/py/pfenv.c
index 15793ff762..965636aea0 100644
--- a/py/pfenv.c
+++ b/py/pfenv.c
@@ -46,11 +46,11 @@
 static const char pad_spaces[] = "                ";
 static const char pad_zeroes[] = "0000000000000000";
 
-void pfenv_vstr_add_strn(void *data, const char *str, unsigned int len){
+void pfenv_vstr_add_strn(void *data, const char *str, mp_uint_t len){
     vstr_add_strn(data, str, len);
 }
 
-int pfenv_print_strn(const pfenv_t *pfenv, const char *str, unsigned int len, int flags, char fill, int width) {
+int pfenv_print_strn(const pfenv_t *pfenv, const char *str, mp_uint_t len, int flags, char fill, int width) {
     int left_pad = 0;
     int right_pad = 0;
     int pad = width - len;
@@ -234,8 +234,8 @@ int pfenv_print_mp_int(const pfenv_t *pfenv, mp_obj_t x, int sgn, int base, int
     // enough, a dynamic one will be allocated.
     char stack_buf[sizeof(mp_int_t) * 4];
     char *buf = stack_buf;
-    int buf_size = sizeof(stack_buf);
-    int fmt_size = 0;
+    mp_uint_t buf_size = sizeof(stack_buf);
+    mp_uint_t fmt_size = 0;
     char *str;
 
     if (prec > 1) {
diff --git a/py/pfenv.h b/py/pfenv.h
index 781738f4db..fea2c883e9 100644
--- a/py/pfenv.h
+++ b/py/pfenv.h
@@ -38,12 +38,12 @@
 
 typedef struct _pfenv_t {
     void *data;
-    void (*print_strn)(void *, const char *str, unsigned int len);
+    void (*print_strn)(void *, const char *str, mp_uint_t len);
 } pfenv_t;
 
-void pfenv_vstr_add_strn(void *data, const char *str, unsigned int len);
+void pfenv_vstr_add_strn(void *data, const char *str, mp_uint_t len);
 
-int pfenv_print_strn(const pfenv_t *pfenv, const char *str, unsigned int len, int flags, char fill, int width);
+int pfenv_print_strn(const pfenv_t *pfenv, const char *str, mp_uint_t len, int flags, char fill, int width);
 int pfenv_print_int(const pfenv_t *pfenv, mp_uint_t x, int sgn, int base, int base_char, int flags, char fill, int width);
 int pfenv_print_mp_int(const pfenv_t *pfenv, mp_obj_t x, int sgn, int base, int base_char, int flags, char fill, int width, int prec);
 #if MICROPY_PY_BUILTINS_FLOAT
diff --git a/py/repl.c b/py/repl.c
index 2c3dfbd4d9..66a67e3d5b 100644
--- a/py/repl.c
+++ b/py/repl.c
@@ -31,7 +31,7 @@
 #if MICROPY_HELPER_REPL
 
 bool str_startswith_word(const char *str, const char *head) {
-    int i;
+    mp_uint_t i;
     for (i = 0; str[i] && head[i]; i++) {
         if (str[i] != head[i]) {
             return false;
diff --git a/py/sequence.c b/py/sequence.c
index 6e92b6b7a0..8cc7519be8 100644
--- a/py/sequence.c
+++ b/py/sequence.c
@@ -44,7 +44,7 @@
 // Implements backend of sequence * integer operation. Assumes elements are
 // memory-adjacent in sequence.
 void mp_seq_multiply(const void *items, mp_uint_t item_sz, mp_uint_t len, mp_uint_t times, void *dest) {
-    for (int i = 0; i < times; i++) {
+    for (mp_uint_t i = 0; i < times; i++) {
         uint copy_sz = item_sz * len;
         memcpy(dest, items, copy_sz);
         dest = (char*)dest + copy_sz;
@@ -185,8 +185,8 @@ bool mp_seq_cmp_objs(mp_uint_t op, const mp_obj_t *items1, mp_uint_t len1, const
         }
     }
 
-    int len = len1 < len2 ? len1 : len2;
-    for (int i = 0; i < len; i++) {
+    mp_uint_t len = len1 < len2 ? len1 : len2;
+    for (mp_uint_t i = 0; i < len; i++) {
         // If current elements equal, can't decide anything - go on
         if (mp_obj_equal(items1[i], items2[i])) {
             continue;
diff --git a/py/showbc.c b/py/showbc.c
index 67c5d7adea..c25cec85d1 100644
--- a/py/showbc.c
+++ b/py/showbc.c
@@ -57,9 +57,7 @@
     ip += sizeof(mp_uint_t); \
 } while (0)
 
-void mp_bytecode_print2(const byte *ip, int len);
-
-void mp_bytecode_print(const void *descr, const byte *ip, int len) {
+void mp_bytecode_print(const void *descr, const byte *ip, mp_uint_t len) {
     const byte *ip_start = ip;
 
     // get code info size
@@ -115,14 +113,13 @@ void mp_bytecode_print(const void *descr, const byte *ip, int len) {
     mp_bytecode_print2(ip, len - 0);
 }
 
-void mp_bytecode_print2(const byte *ip, int len) {
+void mp_bytecode_print2(const byte *ip, mp_uint_t len) {
     const byte *ip_start = ip;
     mp_uint_t unum;
     qstr qstr;
     while (ip - ip_start < len) {
         printf("%02u ", (uint)(ip - ip_start));
-        int op = *ip++;
-        switch (op) {
+        switch (*ip++) {
             case MP_BC_LOAD_CONST_FALSE:
                 printf("LOAD_CONST_FALSE");
                 break;
@@ -520,7 +517,7 @@ void mp_bytecode_print2(const byte *ip, int len) {
                 break;
 
             default:
-                printf("code %p, byte code 0x%02x not implemented\n", ip, op);
+                printf("code %p, byte code 0x%02x not implemented\n", ip, ip[-1]);
                 assert(0);
                 return;
         }
diff --git a/py/vstr.c b/py/vstr.c
index 3a021a9aee..c23bbaa005 100644
--- a/py/vstr.c
+++ b/py/vstr.c
@@ -263,24 +263,6 @@ copy:
     vstr->buf[vstr->len] = 0;
 }
 
-/*
-void vstr_add_le16(vstr_t *vstr, unsigned short v) {
-    byte *buf = (byte*)vstr_add_len(vstr, 2);
-    if (buf == NULL) {
-        return;
-    }
-    encode_le16(buf, v);
-}
-
-void vstr_add_le32(vstr_t *vstr, unsigned int v) {
-    byte *buf = (byte*)vstr_add_len(vstr, 4);
-    if (buf == NULL) {
-        return;
-    }
-    encode_le32(buf, v);
-}
-*/
-
 char *vstr_ins_blank_bytes(vstr_t *vstr, size_t byte_pos, size_t byte_len) {
     if (vstr->had_error) {
         return NULL;