mirror of
https://github.com/mytechnotalent/Embedded-Hacking.git
synced 2026-05-23 07:59:52 +02:00
Kevin Thomas
69 lines
2.3 KiB
C
69 lines
2.3 KiB
C
/**
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* @file 0x0008_uninitialized-variables.c
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* @brief Uninitialized variables: demonstrate undefined behavior with printf
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* @author Kevin Thomas
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* @date 2025
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*
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* MIT License
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*
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* Copyright (c) 2025 Kevin Thomas
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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* -----------------------------------------------------------------------------
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*
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* Demonstrates the danger of uninitialized variables. Prints the value of an
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* uninitialized uint8_t over UART while blinking an LED on GPIO16.
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*
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* Wiring:
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* GPIO16 -> LED anode (with current-limiting resistor to GND)
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*/
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#include <stdio.h>
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#include "pico/stdlib.h"
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/** @brief GPIO pin number for the LED */
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#define LED_PIN 16
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/**
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* @brief Toggle LED and print uninitialized variable value
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*
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* @details Blinks the LED on and off with a 500ms delay between each
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* transition and prints the age variable each cycle.
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*
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* @param age value to print (uninitialized in this demo)
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*/
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static void blink_and_print(uint8_t age) {
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printf("age: %d\r\n", age);
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gpio_put(LED_PIN, 1);
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sleep_ms(500);
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gpio_put(LED_PIN, 0);
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sleep_ms(500);
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}
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int main(void) {
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uint8_t age;
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stdio_init_all();
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gpio_init(LED_PIN);
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gpio_set_dir(LED_PIN, GPIO_OUT);
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while (true) {
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blink_and_print(age);
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}
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}
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