configASSERT() for development debugging in FreeRTOS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What happens when configASSERT fails in FreeRTOS?

Consider this snippet using configASSERT in FreeRTOS:

void vTaskFunction(void *pvParameters) {
    int x = 0;
    configASSERT(x != 0);
    // Task code
}

What is the expected behavior when this task runs?

FreeRTOS

void vTaskFunction(void *pvParameters) {
    int x = 0;
    configASSERT(x != 0);
    // Task code
}

A The assertion is ignored and a warning message is printed to the console.

B The system automatically restarts the task without any warning.

C The system halts or enters an infinite loop to indicate the assertion failure.

D The task continues running normally without any interruption.

💡 Hint

Think about what an assert is supposed to do when a condition is false during development.

configASSERT is designed to catch programming errors during development by halting the system or entering a safe infinite loop when the condition is false. This helps developers notice and fix bugs early.

🧠 Conceptual

intermediate

Why use configASSERT() only in development builds?

Why is it recommended to enable configASSERT() only during development and disable it in production?

A Because configASSERT() can halt the system, which is undesirable in production environments.

B Because configASSERT() improves system performance in production.

C Because configASSERT() automatically fixes bugs in production code.

D Because configASSERT() disables all interrupts permanently.

💡 Hint

Think about what happens when an assertion fails and why that might be a problem in a live system.

Assertions are meant to catch bugs early by stopping the system. In production, stopping the system abruptly can cause failures or data loss, so assertions are usually disabled.

❓ Predict Output

advanced

What is the output of this configASSERT macro usage?

Given the following configASSERT definition and code snippet:

#define configASSERT(x) if((x) == 0) { taskDISABLE_INTERRUPTS(); for(;;); }

void test() {
    int a = 5;
    configASSERT(a > 10);
    printf("Passed\n");
}

What will be printed when test() is called?

FreeRTOS

#define configASSERT(x) if((x) == 0) { taskDISABLE_INTERRUPTS(); for(;;); }

void test() {
    int a = 5;
    configASSERT(a > 10);
    printf("Passed\n");
}

A Passed

B Nothing is printed; the system enters an infinite loop.

C Compilation error due to missing semicolon.

D Runtime error: division by zero.

💡 Hint

Check the condition inside configASSERT and what happens if it is false.

Since a=5 and the condition a>10 is false, configASSERT triggers the infinite loop after disabling interrupts, so printf is never reached.

🔧 Debug

advanced

Identify the error in this configASSERT usage

What is wrong with this configASSERT usage?

#define configASSERT(x) if(x == 0) { taskDISABLE_INTERRUPTS(); for(;;); }

void check(int val) {
    configASSERT(val > 0);
    printf("Value is %d\n", val);
}

FreeRTOS

#define configASSERT(x) if(x == 0) { taskDISABLE_INTERRUPTS(); for(;;); }

void check(int val) {
    configASSERT(val > 0);
    printf("Value is %d\n", val);
}

A The macro lacks parentheses around the condition, causing incorrect evaluation.

B The macro will cause a syntax error due to missing braces.

C The macro disables interrupts but does not halt the system.

D The macro will always print the value regardless of the assertion.

💡 Hint

Consider operator precedence and how macros evaluate expressions.

Without parentheses around x in the macro, expressions like val > 0 may not evaluate correctly, leading to unexpected behavior.

🚀 Application

expert

How to implement a custom configASSERT handler for debugging?

You want to customize configASSERT to log the file name and line number where the assertion failed before halting. Which of the following implementations correctly achieves this?

FreeRTOS

#define configASSERT(x) // your implementation here

A #define configASSERT(x) if(x) { printf("Assertion failed at %s:%d\n", __FILE__, __LINE__); taskDISABLE_INTERRUPTS(); }

B #define configASSERT(x) if(!(x)) { taskDISABLE_INTERRUPTS(); for(;;); printf("Assertion failed\n"); }

C #define configASSERT(x) if(x == 0) { for(;;); printf("Error at line %d\n", __LINE__); }

D #define configASSERT(x) if((x) == 0) { printf("Assertion failed at %s:%d\n", __FILE__, __LINE__); taskDISABLE_INTERRUPTS(); for(;;); }

💡 Hint

Remember that code after an infinite loop will never run.

Option D prints the failure message before disabling interrupts and entering an infinite loop, ensuring the message is logged before halting.