Clean up various C source and headers to appease -Wstrict-prototypes

In C, func() is a function taking an unspecified number of arguments,
vs func(void) a function taking no arguments. In C++ both forms indicate
"no arguments."

Update these headers to use the (void) form, which is correct in both
languages and avoids complaints when -Wstrict-prototypes is specified.

src/common/pico_base/include/pico/assert.h

@@ -36,7 +36,7 @@ extern "C" {
 #define hard_assert_if(x, test) ({if (PARAM_ASSERTIONS_ENABLED(x)) hard_assert(!(test));})
 
 #ifdef NDEBUG
-extern void hard_assertion_failure();
+extern void hard_assertion_failure(void);
 static inline void hard_assert(bool condition, ...) {
     if (!condition)
         hard_assertion_failure();

src/common/pico_stdlib/include/pico/stdlib.h

@@ -71,14 +71,14 @@ extern "C" {
  *  PICO_DEFAULT_UART_TX_PIN
  *  PICO_DEFAULT_UART_RX_PIN
  */
-void setup_default_uart();
+void setup_default_uart(void);
 
 /*! \brief Initialise the system clock to 48MHz
  *  \ingroup pico_stdlib
  *
  *  Set the system clock to 48MHz, and set the peripheral clock to match.
  */
-void set_sys_clock_48mhz();
+void set_sys_clock_48mhz(void);
 
 /*! \brief Initialise the system clock
  *  \ingroup pico_stdlib

src/common/pico_time/include/pico/time.h

@@ -58,7 +58,7 @@ extern "C" {
  * \sa sleep_until()
  * \sa time_us_64()
  */
-static inline absolute_time_t get_absolute_time() {
+static inline absolute_time_t get_absolute_time(void) {
     absolute_time_t t;
     update_us_since_boot(&t, time_us_64());
     return t;
@@ -350,7 +350,7 @@ typedef struct alarm_pool alarm_pool_t;
  * \brief Create the default alarm pool (if not already created or disabled)
  * \ingroup alarm
  */
-void alarm_pool_init_default();
+void alarm_pool_init_default(void);
 
 #if !PICO_TIME_DEFAULT_ALARM_POOL_DISABLED
 /*!
@@ -360,7 +360,7 @@ void alarm_pool_init_default();
  * \ingroup alarm
  * \sa #PICO_TIME_DEFAULT_ALARM_POOL_HARDWARE_ALARM_NUM
  */
-alarm_pool_t *alarm_pool_get_default();
+alarm_pool_t *alarm_pool_get_default(void);
 #endif
 
 /**

src/rp2_common/hardware_claim/include/hardware/claim.h

@@ -87,7 +87,7 @@ void hw_claim_clear(uint8_t *bits, uint bit_index);
  *
  * \return a token to pass to hw_claim_unlock()
  */
-uint32_t hw_claim_lock();
+uint32_t hw_claim_lock(void);
 
 /*! \brief Release the runtime mutual exclusion lock provided by the `hardware_claim` library
  *  \ingroup hardware_claim

src/rp2_common/hardware_clocks/include/hardware/clocks.h

@@ -99,7 +99,7 @@ extern "C" {
  *
  *  Must be called before any other clock function.
  */
-void clocks_init();
+void clocks_init(void);
 
 /*! \brief Configure the specified clock
  *  \ingroup hardware_clocks

src/rp2_common/hardware_divider/include/hardware/divider.h

@@ -74,7 +74,7 @@ static inline void hw_divider_divmod_u32_start(uint32_t a, uint32_t b) {
  *
  * Wait for a divide to complete
  */
-static inline void hw_divider_wait_ready() {
+static inline void hw_divider_wait_ready(void) {
     // this is #1 in lsr below
     static_assert(SIO_DIV_CSR_READY_BITS == 1, "");
 
@@ -99,7 +99,7 @@ static inline void hw_divider_wait_ready() {
  *
  * \return Current result. Most significant 32 bits are the remainder, lower 32 bits are the quotient.
  */
-static inline divmod_result_t hw_divider_result_nowait() {
+static inline divmod_result_t hw_divider_result_nowait(void) {
     // as ugly as this looks it is actually quite efficient
     divmod_result_t rc = (((divmod_result_t) sio_hw->div_remainder) << 32u) | sio_hw->div_quotient;
     return rc;
@@ -112,7 +112,7 @@ static inline divmod_result_t hw_divider_result_nowait() {
  *
  * \return Current result. Most significant 32 bits are the remainder, lower 32 bits are the quotient.
  */
-static inline divmod_result_t hw_divider_result_wait() {
+static inline divmod_result_t hw_divider_result_wait(void) {
     hw_divider_wait_ready();
     return hw_divider_result_nowait();
 }
@@ -124,7 +124,7 @@ static inline divmod_result_t hw_divider_result_wait() {
  *
  * \return Current unsigned quotient result.
  */
-static inline uint32_t hw_divider_u32_quotient_wait() {
+static inline uint32_t hw_divider_u32_quotient_wait(void) {
     hw_divider_wait_ready();
     return sio_hw->div_quotient;
 }
@@ -136,7 +136,7 @@ static inline uint32_t hw_divider_u32_quotient_wait() {
  *
  * \return Current signed quotient result.
  */
-static inline int32_t hw_divider_s32_quotient_wait() {
+static inline int32_t hw_divider_s32_quotient_wait(void) {
     hw_divider_wait_ready();
     return sio_hw->div_quotient;
 }
@@ -148,7 +148,7 @@ static inline int32_t hw_divider_s32_quotient_wait() {
  *
  * \return Current unsigned remainder result.
  */
-static inline uint32_t hw_divider_u32_remainder_wait() {
+static inline uint32_t hw_divider_u32_remainder_wait(void) {
     hw_divider_wait_ready();
     int32_t rc = sio_hw->div_remainder;
     sio_hw->div_quotient; // must read quotient to cooperate with other SDK code
@@ -162,7 +162,7 @@ static inline uint32_t hw_divider_u32_remainder_wait() {
  *
  * \return Current remainder results.
  */
-static inline int32_t hw_divider_s32_remainder_wait() {
+static inline int32_t hw_divider_s32_remainder_wait(void) {
     hw_divider_wait_ready();
     int32_t rc = sio_hw->div_remainder;
     sio_hw->div_quotient; // must read quotient to cooperate with other SDK code
@@ -290,7 +290,7 @@ static inline int32_t hw_divider_remainder_s32(int32_t a, int32_t b) {
 /*! \brief Pause for exact amount of time needed for a asynchronous divide to complete
  *  \ingroup hardware_divider
  */
-static inline void hw_divider_pause() {
+static inline void hw_divider_pause(void) {
     asm volatile (
     "b _1_%=\n"
     "_1_%=:\n"

src/rp2_common/hardware_dma/include/hardware/dma.h

@@ -595,7 +595,7 @@ inline static void dma_sniffer_set_byte_swap_enabled(bool swap) {
  *  \ingroup hardware_dma
  *
  */
-inline static void dma_sniffer_disable() {
+inline static void dma_sniffer_disable(void) {
     dma_hw->sniff_ctrl = 0;
 }
 

src/rp2_common/hardware_flash/flash.c

@@ -33,7 +33,7 @@
 static uint32_t boot2_copyout[BOOT2_SIZE_WORDS];
 static bool boot2_copyout_valid = false;
 
-static void __no_inline_not_in_flash_func(flash_init_boot2_copyout)() {
+static void __no_inline_not_in_flash_func(flash_init_boot2_copyout)(void) {
     if (boot2_copyout_valid)
         return;
     for (int i = 0; i < BOOT2_SIZE_WORDS; ++i)
@@ -42,15 +42,15 @@ static void __no_inline_not_in_flash_func(flash_init_boot2_copyout)() {
     boot2_copyout_valid = true;
 }
 
-static void __no_inline_not_in_flash_func(flash_enable_xip_via_boot2)() {
+static void __no_inline_not_in_flash_func(flash_enable_xip_via_boot2)(void) {
     ((void (*)(void))boot2_copyout+1)();
 }
 
 #else
 
-static void __no_inline_not_in_flash_func(flash_init_boot2_copyout)() {}
+static void __no_inline_not_in_flash_func(flash_init_boot2_copyout)(void) {}
 
-static void __no_inline_not_in_flash_func(flash_enable_xip_via_boot2)() {
+static void __no_inline_not_in_flash_func(flash_enable_xip_via_boot2)(void) {
     // Set up XIP for 03h read on bus access (slow but generic)
     void (*flash_enter_cmd_xip)(void) = (void(*)(void))rom_func_lookup(rom_table_code('C', 'X'));
     assert(flash_enter_cmd_xip);

src/rp2_common/hardware_gpio/include/hardware/gpio.h

@@ -335,7 +335,7 @@ static inline bool gpio_get(uint gpio) {
  *
  * \return Bitmask of raw GPIO values, as bits 0-29
  */
-static inline uint32_t gpio_get_all() {
+static inline uint32_t gpio_get_all(void) {
     return sio_hw->gpio_in;
 }
 
@@ -490,7 +490,7 @@ static inline uint gpio_get_dir(uint gpio) {
     return gpio_is_dir_out(gpio); // note GPIO_OUT is 1/true and GPIO_IN is 0/false anyway
 }
 
-extern void gpio_debug_pins_init();
+extern void gpio_debug_pins_init(void);
 
 #ifdef __cplusplus
 }

src/rp2_common/hardware_interp/include/hardware/interp.h

@@ -231,7 +231,7 @@ static inline void interp_config_set_force_bits(interp_config *c, uint bits) {
  *
  * \return A default interpolation configuration
  */
-static inline interp_config interp_default_config() {
+static inline interp_config interp_default_config(void) {
     interp_config c = {0};
     // Just pass through everything
     interp_config_set_mask(&c, 0, 31);

src/rp2_common/hardware_irq/include/hardware/irq.h

@@ -116,7 +116,7 @@ extern "C" {
  *
  * All interrupts handlers should be of this type, and follow normal ARM EABI register saving conventions
  */
-typedef void (*irq_handler_t)();
+typedef void (*irq_handler_t)(void);
 
 /*! \brief Set specified interrupts priority
  *  \ingroup hardware_irq
@@ -255,7 +255,7 @@ void irq_set_pending(uint num);
  *
  * \note This is an internal method and user should generally not call it.
  */
-void irq_init_priorities();
+void irq_init_priorities(void);
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/hardware_irq/irq.c

@@ -12,10 +12,10 @@
 #include "pico/mutex.h"
 #include "pico/assert.h"
 
-extern void __unhandled_user_irq();
-extern uint __get_current_exception();
+extern void __unhandled_user_irq(void);
+extern uint __get_current_exception(void);
 
-static inline irq_handler_t *get_vtable() {
+static inline irq_handler_t *get_vtable(void) {
     return (irq_handler_t *) scb_hw->vtor;
 }
 
@@ -69,8 +69,8 @@ void irq_set_pending(uint num) {
 static_assert(PICO_MAX_SHARED_IRQ_HANDLERS >= 1 && PICO_MAX_SHARED_IRQ_HANDLERS < 0x7f, "");
 
 // note these are not real functions, they are code fragments (i.e. don't call them)
-extern void irq_handler_chain_first_slot();
-extern void irq_handler_chain_remove_tail();
+extern void irq_handler_chain_first_slot(void);
+extern void irq_handler_chain_remove_tail(void);
 
 extern struct irq_handler_chain_slot {
     // first 3 half words are executable code (raw vtable handler points to one slot, and inst3 will jump to next

src/rp2_common/hardware_pio/include/hardware/pio.h

@@ -354,7 +354,7 @@ static inline void sm_config_set_mov_status(pio_sm_config *c, enum pio_mov_statu
  *
  * \return the default state machine configuration which can then be modified.
  */
-static inline pio_sm_config pio_get_default_sm_config() {
+static inline pio_sm_config pio_get_default_sm_config(void) {
     pio_sm_config c = {0, 0, 0};
     sm_config_set_clkdiv_int_frac(&c, 1, 0);
     sm_config_set_wrap(&c, 0, 31);

src/rp2_common/hardware_pio/include/hardware/pio_instructions.h

@@ -167,7 +167,7 @@ inline static uint pio_encode_set(enum pio_src_dest dest, uint value) {
     return _pio_encode_instr_and_src_dest(pio_instr_bits_set, dest, value);
 }
 
-inline static uint pio_encode_nop() {
+inline static uint pio_encode_nop(void) {
     return pio_encode_mov(pio_y, pio_y);
 }
 

src/rp2_common/hardware_pwm/include/hardware/pwm.h

@@ -199,7 +199,7 @@ static inline void pwm_init(uint slice_num, pwm_config *c, bool start) {
  *
  * \return Set of default values.
  */
-static inline pwm_config pwm_get_default_config() {
+static inline pwm_config pwm_get_default_config(void) {
     pwm_config c = {0, 0, 0};
     pwm_config_set_phase_correct(&c, false);
     pwm_config_set_clkdiv_int(&c, 1);
@@ -471,7 +471,7 @@ static inline void pwm_clear_irq(uint slice_num) {
  *
  * \return Bitmask of all PWM interrupts currently set
  */
-static inline int32_t pwm_get_irq_status_mask() {
+static inline int32_t pwm_get_irq_status_mask(void) {
     return pwm_hw->ints;
 }
 

src/rp2_common/hardware_sync/include/hardware/sync.h

@@ -81,7 +81,7 @@ typedef volatile uint32_t spin_lock_t;
 
  * The SEV (send event) instruction sends an event to both cores.
  */
-inline static void __sev() {
+inline static void __sev(void) {
     __asm volatile ("sev");
 }
 
@@ -91,7 +91,7 @@ inline static void __sev() {
  * The WFE (wait for event) instruction waits until one of a number of
  * events occurs, including events signalled by the SEV instruction on either core.
  */
-inline static void __wfe() {
+inline static void __wfe(void) {
     __asm volatile ("wfe");
 }
 
@@ -100,7 +100,7 @@ inline static void __wfe() {
 *
  * The WFI (wait for interrupt) instruction waits for a interrupt to wake up the core.
  */
-inline static void __wfi() {
+inline static void __wfi(void) {
     __asm volatile ("wfi");
 }
 
@@ -110,7 +110,7 @@ inline static void __wfi() {
  * The DMB (data memory barrier) acts as a memory barrier, all memory accesses prior to this
  * instruction will be observed before any explicit access after the instruction.
  */
-inline static void __dmb() {
+inline static void __dmb(void) {
     __asm volatile ("dmb");
 }
 
@@ -121,14 +121,14 @@ inline static void __dmb() {
  * so that all instructions following the ISB are fetched from cache or memory again, after
  * the ISB instruction has been completed.
  */
-inline static void __isb() {
+inline static void __isb(void) {
     __asm volatile ("isb");
 }
 
 /*! \brief Acquire a memory fence
  *  \ingroup hardware_sync
  */
-inline static void __mem_fence_acquire() {
+inline static void __mem_fence_acquire(void) {
     // the original code below makes it hard for us to be included from C++ via a header
     // which itself is in an extern "C", so just use __dmb instead, which is what
     // is required on Cortex M0+
@@ -144,7 +144,7 @@ inline static void __mem_fence_acquire() {
  *  \ingroup hardware_sync
  *
  */
-inline static void __mem_fence_release() {
+inline static void __mem_fence_release(void) {
     // the original code below makes it hard for us to be included from C++ via a header
     // which itself is in an extern "C", so just use __dmb instead, which is what
     // is required on Cortex M0+
@@ -161,7 +161,7 @@ inline static void __mem_fence_release() {
  *
  * \return The prior interrupt enable status for restoration later via restore_interrupts()
  */
-inline static uint32_t save_and_disable_interrupts() {
+inline static uint32_t save_and_disable_interrupts(void) {
     uint32_t status;
     __asm volatile ("mrs %0, PRIMASK" : "=r" (status)::);
     __asm volatile ("cpsid i");
@@ -266,7 +266,7 @@ inline static void spin_unlock(spin_lock_t *lock, uint32_t saved_irq) {
  *
  * \return The core number the call was made from
  */
-static inline uint get_core_num() {
+static inline uint get_core_num(void) {
     return (*(uint32_t *) (SIO_BASE + SIO_CPUID_OFFSET));
 }
 
@@ -286,7 +286,7 @@ spin_lock_t *spin_lock_init(uint lock_num);
 void spin_locks_reset(void);
 
 // this number is not claimed
-uint next_striped_spin_lock_num();
+uint next_striped_spin_lock_num(void);
 
 /*! \brief Mark a spin lock as used
  *  \ingroup hardware_sync

src/rp2_common/hardware_timer/include/hardware/timer.h

@@ -62,7 +62,7 @@ static inline void check_hardware_alarm_num_param(uint alarm_num) {
 *
 * \return the 32 bit timestamp
 */
-static inline uint32_t time_us_32() {
+static inline uint32_t time_us_32(void) {
     return timer_hw->timerawl;
 }
 
@@ -75,7 +75,7 @@ static inline uint32_t time_us_32() {
 *
 * \return the 64 bit timestamp
 */
-uint64_t time_us_64();
+uint64_t time_us_64(void);
 
 /*! \brief Busy wait wasting cycles for the given (32 bit) number of microseconds
  *  \ingroup hardware_timer

src/rp2_common/hardware_timer/timer.c

@@ -92,7 +92,7 @@ static inline uint harware_alarm_irq_number(uint alarm_num) {
     return TIMER_IRQ_0 + alarm_num;
 }
 
-static void hardware_alarm_irq_handler() {
+static void hardware_alarm_irq_handler(void) {
     // Determine which timer this IRQ is for
     uint32_t ipsr;
     __asm volatile ("mrs %0, ipsr" : "=r" (ipsr)::);

src/rp2_common/hardware_uart/include/hardware/uart.h

@@ -413,7 +413,7 @@ void uart_set_translate_crlf(uart_inst_t *uart, bool translate);
 /*! \brief Wait for the default UART'S TX fifo to be drained
  *  \ingroup hardware_uart
  */
-static inline void uart_default_tx_wait_blocking() {
+static inline void uart_default_tx_wait_blocking(void) {
     uart_tx_wait_blocking(uart_default);
 }
 

src/rp2_common/pico_double/double_init_rom.c

@@ -17,9 +17,9 @@ static __attribute__((noreturn)) void missing_double_func_shim() {
     panic("missing double function");
 }
 #endif
-extern void double_table_shim_on_use_helper();
+extern void double_table_shim_on_use_helper(void);
 
-void __aeabi_double_init() {
+void __aeabi_double_init(void) {
     int rom_version = rp2040_rom_version();
 #if PICO_DOUBLE_SUPPORT_ROM_V1
     if (rom_version == 1) {

src/rp2_common/pico_float/float_init_rom.c

@@ -19,13 +19,13 @@ static __attribute__((noreturn)) void missing_float_func_shim() {
 }
 #endif
 
-void __aeabi_float_init() {
+void __aeabi_float_init(void) {
     int rom_version = rp2040_rom_version();
     void *rom_table = rom_data_lookup(rom_table_code('S', 'F'));
 #if PICO_FLOAT_SUPPORT_ROM_V1
     if (rom_version == 1) {
         memcpy(&sf_table, rom_table, SF_TABLE_V1_SIZE);
-        extern void float_table_shim_on_use_helper();
+        extern void float_table_shim_on_use_helper(void);
         // todo replace NDEBUG with a more exclusive assertion guard
 #ifndef NDEBUG
         if (*(uint16_t *)0x29ee != 0x0fc4 || // this is packx

src/rp2_common/pico_multicore/include/pico/multicore.h

@@ -36,7 +36,7 @@ extern "C" {
  *  \ingroup pico_multicore
  *
  */
-void multicore_reset_core1();
+void multicore_reset_core1(void);
 
 /*! \brief  Run code on core 1
  *  \ingroup pico_multicore
@@ -58,7 +58,7 @@ void multicore_launch_core1_with_stack(void (*entry)(void), uint32_t *stack_bott
  *  \ingroup pico_multicore
  *
  */
-void multicore_sleep_core1();
+void multicore_sleep_core1(void);
 
 /*! \brief  Launch code on core 1 with no stack protection
  *  \ingroup pico_multicore
@@ -85,7 +85,7 @@ void multicore_launch_core1_raw(void (*entry)(void), uint32_t *sp, uint32_t vect
  *
  * \return true if the FIFO has data in it, false otherwise
  */
-static inline bool multicore_fifo_rvalid() {
+static inline bool multicore_fifo_rvalid(void) {
     return !!(sio_hw->fifo_st & SIO_FIFO_ST_VLD_BITS);
 }
 
@@ -94,7 +94,7 @@ static inline bool multicore_fifo_rvalid() {
  *
  *  @return true if the FIFO is full, false otherwise
  */
-static inline bool multicore_fifo_wready() {
+static inline bool multicore_fifo_wready(void) {
     return !!(sio_hw->fifo_st & SIO_FIFO_ST_RDY_BITS);
 }
 
@@ -120,7 +120,7 @@ bool multicore_fifo_push_timeout_us(uint32_t data, uint64_t timeout_us);
  *
  * \return 32 bit unsigned data from the FIFO.
  */
-uint32_t multicore_fifo_pop_blocking();
+uint32_t multicore_fifo_pop_blocking(void);
 
 bool multicore_fifo_pop_timeout_us(uint64_t timeout_us, uint32_t *out);
 
@@ -128,7 +128,7 @@ bool multicore_fifo_pop_timeout_us(uint64_t timeout_us, uint32_t *out);
  *  \ingroup multicore_fifo
  *
  */
-static inline void multicore_fifo_drain() {
+static inline void multicore_fifo_drain(void) {
     while (multicore_fifo_rvalid())
         (void) sio_hw->fifo_rd;
 }
@@ -136,7 +136,7 @@ static inline void multicore_fifo_drain() {
 /*! \brief Clear FIFO interrupt
  *  \ingroup multicore_fifo
 */
-static inline void multicore_fifo_clear_irq() {
+static inline void multicore_fifo_clear_irq(void) {
     // Write any value to clear any interrupts
     sio_hw->fifo_st = 0xff;
 }
@@ -153,19 +153,19 @@ static inline void multicore_fifo_clear_irq() {
  * 1 | Value is 1 if this core’s TX FIFO is not full (i.e. if FIFO_WR is ready for more data)
  * 0 | Value is 1 if this core’s RX FIFO is not empty (i.e. if FIFO_RD is valid)
 */
-static inline int32_t multicore_fifo_get_status() {
+static inline int32_t multicore_fifo_get_status(void) {
     return sio_hw->fifo_st;
 }
 
 // call this from the lockout victim thread
-void multicore_lockout_victim_init();
+void multicore_lockout_victim_init(void);
 
 // start locking out the other core (it will be
 bool multicore_lockout_start_timeout_us(uint64_t timeout_us);
-void multicore_lockout_start_blocking();
+void multicore_lockout_start_blocking(void);
 
 bool multicore_lockout_end_timeout_us(uint64_t timeout_us);
-void multicore_lockout_end_blocking();
+void multicore_lockout_end_blocking(void);
 
 #ifdef __cplusplus
 }

src/rp2_common/pico_multicore/multicore.c

@@ -46,7 +46,7 @@ bool multicore_fifo_push_timeout_us(uint32_t data, uint64_t timeout_us) {
     return true;
 }
 
-static inline uint32_t multicore_fifo_pop_blocking_inline() {
+static inline uint32_t multicore_fifo_pop_blocking_inline(void) {
     // If nothing there yet, we wait for an event first,
     // to try and avoid too much busy waiting
     while (!multicore_fifo_rvalid())
@@ -75,7 +75,7 @@ bool multicore_fifo_pop_timeout_us(uint64_t timeout_us, uint32_t *out) {
 // Default stack for core1 ... if multicore_launch_core1 is not included then .stack1 section will be garbage collected
 static uint32_t __attribute__((section(".stack1"))) core1_stack[PICO_CORE1_STACK_SIZE / sizeof(uint32_t)];
 
-static void __attribute__ ((naked)) core1_trampoline() {
+static void __attribute__ ((naked)) core1_trampoline(void) {
     __asm("pop {r0, r1, pc}");
 }
 
@@ -110,7 +110,7 @@ void multicore_sleep_core1() {
     // note we give core1 an invalid stack pointer, as it should not be used
     // note also if we ge simply passed a function that returned immediately, we'd end up in core1_hang anyway
     //  however that would waste 2 bytes for that function (the horror!)
-    extern void core1_hang(); // in crt0.S
+    extern void core1_hang(void); // in crt0.S
     multicore_launch_core1_raw(core1_hang, (uint32_t *) -1, scb_hw->vtor);
 }
 
@@ -161,7 +161,7 @@ static bool lockout_in_progress;
 
 // note this method is in RAM because lockout is used when writing to flash
 // it only makes inline calls
-static void __isr __not_in_flash_func(multicore_lockout_handler)() {
+static void __isr __not_in_flash_func(multicore_lockout_handler)(void) {
     multicore_fifo_clear_irq();
     while (multicore_fifo_rvalid()) {
         if (sio_hw->fifo_rd == LOCKOUT_MAGIC_START) {
@@ -176,7 +176,7 @@ static void __isr __not_in_flash_func(multicore_lockout_handler)() {
     }
 }
 
-static void check_lockout_mutex_init() {
+static void check_lockout_mutex_init(void) {
     // use known available lock - we only need it briefly
     uint32_t save = hw_claim_lock();
     if (!mutex_is_initialzed(&lockout_mutex)) {

src/rp2_common/pico_platform/include/pico/platform.h

@@ -50,7 +50,7 @@ extern "C" {
 
 #define __uninitialized_ram(group) __attribute__((section(".uninitialized_ram." #group))) group
 
-inline static void __breakpoint() {
+inline static void __breakpoint(void) {
     __asm__("bkpt #0");
 }
 
@@ -59,7 +59,7 @@ inline static void __breakpoint() {
 // we provide this macro which allows that code to provide a 64->32 bit mapping in host mode
 #define host_safe_hw_ptr(x) ((uintptr_t)(x))
 
-void __attribute__((noreturn)) panic_unsupported();
+void __attribute__((noreturn)) panic_unsupported(void);
 
 void __attribute__((noreturn)) panic(const char *fmt, ...);
 
@@ -69,19 +69,19 @@ void __attribute__((noreturn)) panic(const char *fmt, ...);
 #endif
 
 #if PICO_NO_FPGA_CHECK
-static inline bool running_on_fpga() {return false;}
+static inline bool running_on_fpga(void) {return false;}
 #else
-bool running_on_fpga();
+bool running_on_fpga(void);
 #endif
 
-uint8_t rp2040_chip_version();
+uint8_t rp2040_chip_version(void);
 
-static inline uint8_t rp2040_rom_version() {
+static inline uint8_t rp2040_rom_version(void) {
     return *(uint8_t*)0x13;
 }
 
 // called by any tight hardware polling loop... nominally empty, but can be modified for debugging
-static inline void tight_loop_contents() {}
+static inline void tight_loop_contents(void) {}
 
 // return a 32 bit handle for a raw ptr; DMA chaining for example embeds pointers in 32 bit values
 // which of course does not work if we're running the code natively on a 64 bit platform for testing.

src/rp2_common/pico_runtime/runtime.c

@@ -87,13 +87,13 @@ void runtime_init(void) {
 
     // Start and end points of the constructor list,
     // defined by the linker script.
-    extern void (*__preinit_array_start)();
-    extern void (*__preinit_array_end)();
+    extern void (*__preinit_array_start)(void);
+    extern void (*__preinit_array_end)(void);
 
     // Call each function in the list.
     // We have to take the address of the symbols, as __preinit_array_start *is*
     // the first function pointer, not the address of it.
-    for (void (**p)() = &__preinit_array_start; p < &__preinit_array_end; ++p) {
+    for (void (**p)(void) = &__preinit_array_start; p < &__preinit_array_end; ++p) {
         (*p)();
     }
 
@@ -144,13 +144,13 @@ void runtime_init(void) {
 
     // Start and end points of the constructor list,
     // defined by the linker script.
-    extern void (*__init_array_start)();
-    extern void (*__init_array_end)();
+    extern void (*__init_array_start)(void);
+    extern void (*__init_array_end)(void);
 
     // Call each function in the list.
     // We have to take the address of the symbols, as __init_array_start *is*
     // the first function pointer, not the address of it.
-    for (void (**p)() = &__init_array_start; p < &__init_array_end; ++p) {
+    for (void (**p)(void) = &__init_array_start; p < &__init_array_end; ++p) {
         (*p)();
     }
 

src/rp2_common/pico_stdio/include/pico/stdio.h

@@ -51,7 +51,7 @@ typedef struct stdio_driver stdio_driver_t;
  *
  * \see stdio_uart, stdio_usb, stdio_semihosting
  */
-void stdio_init_all();
+void stdio_init_all(void);
 
 /*! \brief Initialize all of the present standard stdio types that are linked into the binary.
  * \ingroup pico_stdio
@@ -61,7 +61,7 @@ void stdio_init_all();
  *
  * \see stdio_uart, stdio_usb, stdio_semihosting
  */
-void stdio_flush();
+void stdio_flush(void);
 
 /*! \brief Return a character from stdin if there is one available within a timeout
  * \ingroup pico_stdio

src/rp2_common/pico_stdio/include/pico/stdio/driver.h

@@ -12,7 +12,7 @@
 
 struct stdio_driver {
     void (*out_chars)(const char *buf, int len);
-    void (*out_flush)();
+    void (*out_flush)(void);
     int (*in_chars)(char *buf, int len);
     stdio_driver_t *next;
 #if PICO_STDIO_ENABLE_CRLF_SUPPORT

src/rp2_common/pico_stdio/stdio.c

@@ -33,7 +33,7 @@ static stdio_driver_t *filter;
 #if PICO_STDOUT_MUTEX
 auto_init_mutex(print_mutex);
 
-bool stdout_serialize_begin() {
+bool stdout_serialize_begin(void) {
     int core_num = get_core_num();
     uint32_t owner;
     if (!mutex_try_enter(&print_mutex, &owner)) {
@@ -46,15 +46,15 @@ bool stdout_serialize_begin() {
     return true;
 }
 
-void stdout_serialize_end() {
+void stdout_serialize_end(void) {
     mutex_exit(&print_mutex);
 }
 
 #else
-static bool print_serialize_begin() {
+static bool print_serialize_begin(void) {
     return true;
 }
-static void print_serialize_end() {
+static void print_serialize_end(void) {
 }
 #endif
 
@@ -255,7 +255,7 @@ void stdio_init_all() {
 #endif
 }
 
-int WRAPPER_FUNC(getchar)() {
+int WRAPPER_FUNC(getchar)(void) {
     char buf[1];
     if (0 == stdio_get_until(buf, sizeof(buf), at_the_end_of_time)) {
         return PICO_ERROR_TIMEOUT;

src/rp2_common/pico_stdio_semihosting/include/pico/stdio_semihosting.h

@@ -29,6 +29,6 @@ extern stdio_driver_t stdio_semihosting;
  *
  * \note this method is automatically called by \ref stdio_init_all() if `pico_stdio_semihosting` is included in the build
  */
-void stdio_semihosting_init();
+void stdio_semihosting_init(void);
 
 #endif

src/rp2_common/pico_stdio_uart/include/pico/stdio_uart.h

@@ -33,21 +33,21 @@ extern stdio_driver_t stdio_uart;
  *
  * \note this method is automatically called by \ref stdio_init_all() if `pico_stdio_uart` is included in the build
  */
-void stdio_uart_init();
+void stdio_uart_init(void);
 
 /*! \brief Explicitly initialize stdout only (no stdin) over UART and add it to the current set of stdout drivers
  *  \ingroup pico_stdio_uart
  *
  * This method sets up PICO_DEFAULT_UART_TX_PIN for UART output (if defined) , and configures the baud rate as PICO_DEFAULT_UART_BAUD_RATE
  */
-void stdout_uart_init();
+void stdout_uart_init(void);
 
 /*! \brief Explicitly initialize stdin only (no stdout) over UART and add it to the current set of stdin drivers
  *  \ingroup pico_stdio_uart
  *
  * This method sets up PICO_DEFAULT_UART_RX_PIN for UART input (if defined) , and configures the baud rate as PICO_DEFAULT_UART_BAUD_RATE
  */
-void stdin_uart_init();
+void stdin_uart_init(void);
 
 /*! \brief Perform custom initialization initialize stdin/stdout over UART and add it to the current set of stdin/stdout drivers
  *  \ingroup pico_stdio_uart

src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h

@@ -47,6 +47,6 @@ extern stdio_driver_t stdio_usb;
 /*! \brief Explicitly initialize USB stdio and add it to the current set of stdin drivers
  *  \ingroup pico_stdio_uart
  */
-bool stdio_usb_init();
+bool stdio_usb_init(void);
 
 #endif

src/rp2_common/pico_unique_id/unique_id.c

@@ -11,7 +11,7 @@ static_assert(PICO_UNIQUE_BOARD_ID_SIZE_BYTES == FLASH_UNIQUE_ID_SIZE_BYTES, "Bo
 
 static pico_unique_board_id_t retrieved_id;
 
-static void __attribute__((constructor)) _retrieve_unique_id_on_boot() {
+static void __attribute__((constructor)) _retrieve_unique_id_on_boot(void) {
 #if PICO_NO_FLASH
     // The hardware_flash call will panic() if called directly on a NO_FLASH
     // build. Since this constructor is pre-main it would be annoying to

test/kitchen_sink/CMakeLists.txt

@@ -59,6 +59,7 @@ target_compile_options(kitchen_sink_options INTERFACE
         -Wfloat-equal
         -Wmissing-format-attribute
         -Wno-long-long
+        $<$<COMPILE_LANGUAGE:C>:-Wstrict-prototypes>
 
         # todo not sure these are true, but investigate
         #-Wpacked

test/kitchen_sink/kitchen_sink.c

@@ -39,7 +39,7 @@ uint32_t *foo = (uint32_t *) 200;
 uint32_t dma_to = 0;
 uint32_t dma_from = 0xaaaa5555;
 
-void spiggle() {
+void spiggle(void) {
     dma_channel_config c = dma_channel_get_default_config(1);
     channel_config_set_bswap(&c, true);
     channel_config_set_transfer_data_size(&c, DMA_SIZE_16);
@@ -48,7 +48,7 @@ void spiggle() {
     dma_channel_transfer_from_buffer_now(1, foo, 23);
 }
 
-void __isr dma_handler_a() {
+void __isr dma_handler_a(void) {
     printf("HELLO A\n");
     if (dma_hw->ints1 & 1) {
         dma_hw->ints1 = 1;
@@ -57,7 +57,7 @@ void __isr dma_handler_a() {
     }
 }
 
-void __isr dma_handler_b() {
+void __isr dma_handler_b(void) {
     printf("HELLO B\n");
     if (dma_hw->ints1 & 1) {
         dma_hw->ints1 = 1;
@@ -68,7 +68,7 @@ void __isr dma_handler_b() {
 
 //#pragma GCC pop_options
 
-int main() {
+int main(void) {
     spiggle();
 
     stdio_init_all();