diff --git a/docs/develop/porting.rst b/docs/develop/porting.rst
index 3d0553205c..0511f5d276 100644
--- a/docs/develop/porting.rst
+++ b/docs/develop/porting.rst
@@ -174,9 +174,6 @@ The following is an example of an ``mpconfigport.h`` file:
 
    #define MP_STATE_PORT MP_STATE_VM
 
-   #define MICROPY_PORT_ROOT_POINTERS \
-       const char *readline_hist[8];
-
 This configuration file contains machine-specific configurations including aspects like if different
 MicroPython features should be enabled e.g. ``#define MICROPY_ENABLE_GC (1)``. Making this Setting
 ``(0)`` disables the feature.
diff --git a/examples/embedding/mpconfigport_minimal.h b/examples/embedding/mpconfigport_minimal.h
index 6cc84dcbc1..91b194bc7b 100644
--- a/examples/embedding/mpconfigport_minimal.h
+++ b/examples/embedding/mpconfigport_minimal.h
@@ -87,8 +87,6 @@
 #define MICROPY_PY_UHASHLIB         (0)
 #define MICROPY_PY_UBINASCII        (0)
 
-#define MICROPY_PORT_ROOT_POINTERS \
-
 //////////////////////////////////////////
 // Do not change anything beyond this line
 //////////////////////////////////////////
diff --git a/ports/cc3200/mpconfigport.h b/ports/cc3200/mpconfigport.h
index 58ec80a9f5..ce708cb3f4 100644
--- a/ports/cc3200/mpconfigport.h
+++ b/ports/cc3200/mpconfigport.h
@@ -142,7 +142,6 @@
 // vm state and root pointers for the gc
 #define MP_STATE_PORT MP_STATE_VM
 #define MICROPY_PORT_ROOT_POINTERS                                        \
-    const char *readline_hist[8];                                         \
     mp_obj_t mp_const_user_interrupt;                                     \
     mp_obj_t machine_config_main;                                         \
     mp_obj_list_t pyb_sleep_obj_list;                                     \
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 1877a01437..a374d81203 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -146,7 +146,6 @@ struct mp_bluetooth_nimble_root_pointers_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     mp_obj_t machine_pin_irq_handler[40]; \
     struct _machine_timer_obj_t *machine_timer_obj_head; \
     struct _machine_i2s_obj_t *machine_i2s_obj[I2S_NUM_MAX]; \
diff --git a/ports/esp8266/mpconfigport.h b/ports/esp8266/mpconfigport.h
index 7727f7845a..3f1db723a5 100644
--- a/ports/esp8266/mpconfigport.h
+++ b/ports/esp8266/mpconfigport.h
@@ -148,7 +148,6 @@ extern const struct _mp_print_t mp_debug_print;
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     mp_obj_t pin_irq_handler[16]; \
     byte *uart0_rxbuf; \
 
diff --git a/ports/javascript/Makefile b/ports/javascript/Makefile
index aea9d6ec37..046d303336 100644
--- a/ports/javascript/Makefile
+++ b/ports/javascript/Makefile
@@ -30,7 +30,7 @@ SRC_C = \
 	mphalport.c \
 	modutime.c \
 
-SRC_QSTR += $(SRC_C)
+SRC_QSTR += $(SRC_C) $(SRC_SHARED)
 
 OBJ += $(PY_O)
 OBJ += $(addprefix $(BUILD)/, $(SRC_SHARED:.c=.o))
diff --git a/ports/javascript/mpconfigport.h b/ports/javascript/mpconfigport.h
index 4a6cb45883..01a61e391d 100644
--- a/ports/javascript/mpconfigport.h
+++ b/ports/javascript/mpconfigport.h
@@ -182,6 +182,3 @@ typedef long mp_off_t;
 #define MICROPY_HW_MCU_NAME "Emscripten"
 
 #define MP_STATE_PORT MP_STATE_VM
-
-#define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8];
diff --git a/ports/mimxrt/Makefile b/ports/mimxrt/Makefile
index 7ae3f91837..be1c95ba95 100644
--- a/ports/mimxrt/Makefile
+++ b/ports/mimxrt/Makefile
@@ -290,6 +290,7 @@ SRC_QSTR += \
 	modmimxrt.c \
 	modutime.c \
 	pin.c \
+	shared/readline/readline.c \
 	shared/runtime/mpirq.c \
 	shared/runtime/sys_stdio_mphal.c \
 	$(GEN_PINS_SRC)
diff --git a/ports/mimxrt/mpconfigport.h b/ports/mimxrt/mpconfigport.h
index 1dcaccad47..3bff3e474d 100644
--- a/ports/mimxrt/mpconfigport.h
+++ b/ports/mimxrt/mpconfigport.h
@@ -242,7 +242,6 @@ extern const struct _mp_obj_type_t network_lan_type;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     struct _machine_timer_obj_t *timer_table[MICROPY_HW_PIT_NUM_CHANNELS]; \
     void *machine_pin_irq_objects[MICROPY_HW_NUM_PIN_IRQS]; \
     /* list of registered NICs */ \
diff --git a/ports/minimal/Makefile b/ports/minimal/Makefile
index fc3730e700..ac74925b57 100644
--- a/ports/minimal/Makefile
+++ b/ports/minimal/Makefile
@@ -68,6 +68,7 @@ SRC_C += $(SRC_MOD)
 
 SRC_CXX += $(SRC_MOD_CXX)
 
+SRC_QSTR += shared/readline/readline.c
 SRC_QSTR += $(SRC_MOD) $(SRC_MOD_CXX)
 
 OBJ += $(PY_CORE_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
diff --git a/ports/minimal/mpconfigport.h b/ports/minimal/mpconfigport.h
index 7d6a3adedc..02312e2e40 100644
--- a/ports/minimal/mpconfigport.h
+++ b/ports/minimal/mpconfigport.h
@@ -41,6 +41,3 @@ typedef long mp_off_t;
 #endif
 
 #define MP_STATE_PORT MP_STATE_VM
-
-#define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8];
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 0698a52cef..fcbe71c5a0 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -332,7 +332,6 @@ typedef long mp_off_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     mp_obj_t pin_class_mapper; \
     mp_obj_t pin_class_map_dict; \
     mp_obj_t pin_irq_handlers[NUM_OF_PINS]; \
diff --git a/ports/pic16bit/mpconfigport.h b/ports/pic16bit/mpconfigport.h
index e97a465028..e03fb81a6a 100644
--- a/ports/pic16bit/mpconfigport.h
+++ b/ports/pic16bit/mpconfigport.h
@@ -92,7 +92,6 @@ typedef int mp_off_t;
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    char *readline_hist[8]; \
     mp_obj_t keyboard_interrupt_obj; \
 
 #define MICROPY_MPHALPORT_H "pic16bit_mphal.h"
diff --git a/ports/powerpc/Makefile b/ports/powerpc/Makefile
index a1e6fa4dac..f1ebd6764c 100644
--- a/ports/powerpc/Makefile
+++ b/ports/powerpc/Makefile
@@ -42,6 +42,8 @@ SRC_C = \
 	shared/runtime/stdout_helpers.c \
 	$(BUILD)/_frozen_mpy.c \
 
+SRC_QSTR += shared/readline/readline.c
+
 OBJ = $(PY_CORE_O)
 OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 OBJ += $(BUILD)/head.o
diff --git a/ports/powerpc/mpconfigport.h b/ports/powerpc/mpconfigport.h
index 0b868e3daf..084a461a4a 100644
--- a/ports/powerpc/mpconfigport.h
+++ b/ports/powerpc/mpconfigport.h
@@ -112,9 +112,6 @@ typedef long mp_off_t;
 
 #define MP_STATE_PORT MP_STATE_VM
 
-#define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8];
-
 // powerpc64 gcc doesn't seem to define these
 // These are pointers, so make them 64 bit types
 typedef long intptr_t;
diff --git a/ports/renesas-ra/mpconfigport.h b/ports/renesas-ra/mpconfigport.h
index 64caa69fd2..11b106999a 100644
--- a/ports/renesas-ra/mpconfigport.h
+++ b/ports/renesas-ra/mpconfigport.h
@@ -168,8 +168,6 @@
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
-    \
     mp_obj_t pyb_hid_report_desc; \
     \
     mp_obj_t pyb_config_main; \
diff --git a/ports/rp2/CMakeLists.txt b/ports/rp2/CMakeLists.txt
index 202261f9c1..8f7895459e 100644
--- a/ports/rp2/CMakeLists.txt
+++ b/ports/rp2/CMakeLists.txt
@@ -130,6 +130,7 @@ set(MICROPY_SOURCE_PORT
 
 set(MICROPY_SOURCE_QSTR
     ${MICROPY_SOURCE_PY}
+    ${MICROPY_DIR}/shared/readline/readline.c
     ${MICROPY_DIR}/shared/runtime/mpirq.c
     ${MICROPY_DIR}/shared/runtime/sys_stdio_mphal.c
     ${PROJECT_SOURCE_DIR}/machine_adc.c
diff --git a/ports/rp2/mpconfigport.h b/ports/rp2/mpconfigport.h
index 1a63476c7c..1e85104844 100644
--- a/ports/rp2/mpconfigport.h
+++ b/ports/rp2/mpconfigport.h
@@ -231,7 +231,6 @@ extern const struct _mod_network_nic_type_t mod_network_nic_type_wiznet5k;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     void *machine_pin_irq_obj[30]; \
     void *rp2_pio_irq_obj[2]; \
     void *rp2_state_machine_irq_obj[8]; \
diff --git a/ports/samd/Makefile b/ports/samd/Makefile
index 17dd811690..b3d6d8b228 100644
--- a/ports/samd/Makefile
+++ b/ports/samd/Makefile
@@ -127,6 +127,7 @@ SRC_QSTR += \
 	machine_led.c \
 	modsamd.c \
 	samd_flash.c \
+	shared/readline/readline.c \
 
 SRC_QSTR += $(SRC_MOD) $(SRC_CXX)
 
diff --git a/ports/samd/mpconfigport.h b/ports/samd/mpconfigport.h
index 1625496a2e..96d34bf4da 100644
--- a/ports/samd/mpconfigport.h
+++ b/ports/samd/mpconfigport.h
@@ -99,9 +99,6 @@
 #define mp_type_fileio mp_type_vfs_lfs1_fileio
 #define mp_type_textio mp_type_vfs_lfs1_textio
 
-#define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8];
-
 #define MP_STATE_PORT MP_STATE_VM
 
 // Miscellaneous settings
diff --git a/ports/stm32/mpconfigport.h b/ports/stm32/mpconfigport.h
index a87fe3768f..4afad339bd 100644
--- a/ports/stm32/mpconfigport.h
+++ b/ports/stm32/mpconfigport.h
@@ -258,8 +258,6 @@ struct _mp_bluetooth_btstack_root_pointers_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
-    \
     mp_obj_t pyb_hid_report_desc; \
     \
     mp_obj_t pyb_config_main; \
diff --git a/ports/teensy/mpconfigport.h b/ports/teensy/mpconfigport.h
index db1f56757a..b870263dfc 100644
--- a/ports/teensy/mpconfigport.h
+++ b/ports/teensy/mpconfigport.h
@@ -42,7 +42,6 @@ extern const struct _mp_obj_module_t pyb_module;
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     mp_obj_t pin_class_mapper; \
     mp_obj_t pin_class_map_dict; \
     struct _pyb_uart_obj_t *pyb_stdio_uart; \
diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
index 232bfb857c..4594b8be9d 100644
--- a/ports/unix/mpconfigport.h
+++ b/ports/unix/mpconfigport.h
@@ -129,6 +129,9 @@
 #define MICROPY_READER_POSIX        (1)
 #define MICROPY_READER_VFS          (1)
 #define MICROPY_USE_READLINE_HISTORY (1)
+#ifndef MICROPY_READLINE_HISTORY_SIZE
+#define MICROPY_READLINE_HISTORY_SIZE 50
+#endif
 #define MICROPY_HELPER_LEXER_UNIX   (1)
 #ifndef MICROPY_FLOAT_IMPL
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
@@ -302,7 +305,6 @@ struct _mp_bluetooth_nimble_malloc_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[50]; \
     void *mmap_region_head; \
     MICROPY_BLUETOOTH_ROOT_POINTERS \
 
diff --git a/ports/windows/mpconfigport.h b/ports/windows/mpconfigport.h
index 47292b3bb6..39f8c0059c 100644
--- a/ports/windows/mpconfigport.h
+++ b/ports/windows/mpconfigport.h
@@ -33,6 +33,12 @@
 #ifndef MICROPY_USE_READLINE
 #define MICROPY_USE_READLINE        (1)
 #endif
+#ifndef MICROPY_USE_READLINE_HISTORY
+#define MICROPY_USE_READLINE_HISTORY (1)
+#endif
+#ifndef MICROPY_READLINE_HISTORY_SIZE
+#define MICROPY_READLINE_HISTORY_SIZE (50)
+#endif
 
 #define MICROPY_ALLOC_PATH_MAX      (260) // see minwindef.h for msvc or limits.h for mingw
 #define MICROPY_PERSISTENT_CODE_LOAD (1)
@@ -52,7 +58,6 @@
 #define MICROPY_DEBUG_PRINTERS      (1)
 #define MICROPY_READER_POSIX        (1)
 #define MICROPY_READER_VFS          (1)
-#define MICROPY_USE_READLINE_HISTORY (1)
 #define MICROPY_HELPER_REPL         (1)
 #define MICROPY_REPL_EMACS_KEYS     (1)
 #define MICROPY_REPL_AUTO_INDENT    (1)
@@ -210,11 +215,6 @@ typedef long long mp_off_t;
 typedef long mp_off_t;
 #endif
 
-#if MICROPY_USE_READLINE == 1
-#define MICROPY_PORT_ROOT_POINTERS \
-    char *readline_hist[50];
-#endif
-
 #define MP_STATE_PORT               MP_STATE_VM
 
 #define MICROPY_MPHALPORT_H         "windows_mphal.h"
diff --git a/ports/zephyr/mpconfigport.h b/ports/zephyr/mpconfigport.h
index 26610ccced..1be755baab 100644
--- a/ports/zephyr/mpconfigport.h
+++ b/ports/zephyr/mpconfigport.h
@@ -134,7 +134,6 @@ typedef long mp_off_t;
 #define MP_STATE_PORT MP_STATE_VM
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8]; \
     void *machine_pin_irq_list; /* Linked list of pin irq objects */ \
     struct _mp_bluetooth_zephyr_root_pointers_t *bluetooth_zephyr_root_pointers;
 
diff --git a/ports/zephyr/mpconfigport_minimal.h b/ports/zephyr/mpconfigport_minimal.h
index f0e57d7566..e819d5cf41 100644
--- a/ports/zephyr/mpconfigport_minimal.h
+++ b/ports/zephyr/mpconfigport_minimal.h
@@ -83,6 +83,3 @@ typedef unsigned mp_uint_t; // must be pointer size
 typedef long mp_off_t;
 
 #define MP_STATE_PORT MP_STATE_VM
-
-#define MICROPY_PORT_ROOT_POINTERS \
-    const char *readline_hist[8];
diff --git a/py/mpconfig.h b/py/mpconfig.h
index d70d39ae97..adaa3ec1fb 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -699,6 +699,11 @@
 #define MICROPY_REPL_EVENT_DRIVEN (0)
 #endif
 
+// The number of items to keep in the readline history.
+#ifndef MICROPY_READLINE_HISTORY_SIZE
+#define MICROPY_READLINE_HISTORY_SIZE (8)
+#endif
+
 // Whether to include lexer helper function for unix
 #ifndef MICROPY_HELPER_LEXER_UNIX
 #define MICROPY_HELPER_LEXER_UNIX (0)
diff --git a/shared/readline/readline.c b/shared/readline/readline.c
index 9b8961712d..b85bbd5bea 100644
--- a/shared/readline/readline.c
+++ b/shared/readline/readline.c
@@ -40,16 +40,19 @@
 #define DEBUG_printf(...) (void)0
 #endif
 
-#define READLINE_HIST_SIZE (MP_ARRAY_SIZE(MP_STATE_PORT(readline_hist)))
-
 // flags for readline_t.auto_indent_state
 #define AUTO_INDENT_ENABLED (0x01)
 #define AUTO_INDENT_JUST_ADDED (0x02)
 
 enum { ESEQ_NONE, ESEQ_ESC, ESEQ_ESC_BRACKET, ESEQ_ESC_BRACKET_DIGIT, ESEQ_ESC_O };
 
+#ifdef _MSC_VER
+// work around MSVC compiler bug: https://stackoverflow.com/q/62259834/1976323
+#pragma warning(disable : 4090)
+#endif
+
 void readline_init0(void) {
-    memset(MP_STATE_PORT(readline_hist), 0, READLINE_HIST_SIZE * sizeof(const char*));
+    memset(MP_STATE_PORT(readline_hist), 0, MICROPY_READLINE_HISTORY_SIZE * sizeof(const char*));
 }
 
 STATIC char *str_dup_maybe(const char *str) {
@@ -334,7 +337,7 @@ backward_kill_word:
 up_arrow_key:
 #endif
                 // up arrow
-                if (rl.hist_cur + 1 < (int)READLINE_HIST_SIZE && MP_STATE_PORT(readline_hist)[rl.hist_cur + 1] != NULL) {
+                if (rl.hist_cur + 1 < MICROPY_READLINE_HISTORY_SIZE && MP_STATE_PORT(readline_hist)[rl.hist_cur + 1] != NULL) {
                     // increase hist num
                     rl.hist_cur += 1;
                     // set line to history
@@ -570,10 +573,12 @@ void readline_push_history(const char *line) {
         // so update the history
         char *most_recent_hist = str_dup_maybe(line);
         if (most_recent_hist != NULL) {
-            for (int i = READLINE_HIST_SIZE - 1; i > 0; i--) {
+            for (int i = MICROPY_READLINE_HISTORY_SIZE - 1; i > 0; i--) {
                 MP_STATE_PORT(readline_hist)[i] = MP_STATE_PORT(readline_hist)[i - 1];
             }
             MP_STATE_PORT(readline_hist)[0] = most_recent_hist;
         }
     }
 }
+
+MP_REGISTER_ROOT_POINTER(const char *readline_hist[MICROPY_READLINE_HISTORY_SIZE]);