common: fix UB in some bit shifts

Fix a few instances of undefined behavior (that I'm not yet aware of any
concrete consequences of) in left shift expressions. Roughly, it's
undefined behavior to shift a `1` into the sign bit of a signed type.

Operands in bit shift expressions undergo integer promotions, but not
the usual arithmetic conversions. Notably, the second operand can't
promote the first operand to unsigned. Shifting `1` rather than `1U` can
lead to shifting a `1` into the sign bit, causing undefined behavior.

Relatedly, the integer promotions on a 32-bit platform will usually
promote `uint16_t` to a signed `int`, leading to undefined behavior in
left shift expressions.

src/platforms/common/stm32/gpio.h

@@ -46,10 +46,10 @@ static inline void bmp_gpio_clear(const uint32_t gpioport, const uint16_t gpios)
 #else
 #if defined(STM32F4) || defined(STM32F7)
 	/* NOLINTNEXTLINE(clang-diagnostic-int-to-pointer-cast) */
-	GPIO_BSRR(gpioport) = gpios << 16U;
+	GPIO_BSRR(gpioport) = (uint32_t)gpios << 16U;
 #endif
 	/* NOLINTNEXTLINE(clang-diagnostic-int-to-pointer-cast) */
-	GPIO_BSRR(gpioport) = gpios << 16U;
+	GPIO_BSRR(gpioport) = (uint32_t)gpios << 16U;
 #endif
 }
 

src/platforms/common/swdptap.c

@@ -151,7 +151,7 @@ static void swdptap_seq_out_clk_delay(const uint32_t tms_states, const size_t cl
 {
 	for (size_t cycle = 0; cycle < clock_cycles; ++cycle) {
 		gpio_clear(SWCLK_PORT, SWCLK_PIN);
-		gpio_set_val(SWDIO_PORT, SWDIO_PIN, tms_states & (1 << cycle));
+		gpio_set_val(SWDIO_PORT, SWDIO_PIN, tms_states & (1U << cycle));
 		for (volatile uint32_t counter = target_clk_divider; counter > 0; --counter)
 			continue;
 		gpio_set(SWCLK_PORT, SWCLK_PIN);
@@ -167,7 +167,7 @@ static void swdptap_seq_out_no_delay(const uint32_t tms_states, const size_t clo
 {
 	for (size_t cycle = 0; cycle < clock_cycles; ++cycle) {
 		gpio_clear(SWCLK_PORT, SWCLK_PIN);
-		gpio_set_val(SWDIO_PORT, SWDIO_PIN, tms_states & (1 << cycle));
+		gpio_set_val(SWDIO_PORT, SWDIO_PIN, tms_states & (1U << cycle));
 		gpio_set(SWCLK_PORT, SWCLK_PIN);
 	}
 	gpio_clear(SWCLK_PORT, SWCLK_PIN);