Setting breakpoints in embedded in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a breakpoint using the debugger keyword.

Embedded C

void main() {
    int x = 5;
    [1];
    x = x + 1;
}

Drag options to blanks, or click blank then click option'

A__asm__("int3")

Bbreakpoint()

Cdebugger

Dbreak

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'break' keyword which is for loops or switches, not breakpoints.

Using 'debugger' which is a JavaScript keyword, not C.

In embedded C, setting a breakpoint can be done using an assembly instruction like int3 which triggers a breakpoint interrupt.

2fill in blank

medium

Complete the code to declare a volatile variable to help with debugging.

Embedded C

volatile int [1] = 0;

void main() {
    while(1) {
        [1]++;
    }
}

Drag options to blanks, or click blank then click option'

Aflag

Btemp

Cdebug_var

Dcounter

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that are too generic or unrelated to counting.

Not declaring the variable as volatile.

Declaring a variable as volatile tells the compiler not to optimize it away, which is useful for debugging.

3fill in blank

hard

Fix the error in the code to correctly trigger a breakpoint using inline assembly.

Embedded C

void trigger_breakpoint() {
    __asm__ [1];
}

Drag options to blanks, or click blank then click option'

A("halt")

B("int3")

C("trap")

D("break")

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect assembly instructions like 'break' or 'halt'.

Missing parentheses or quotes around the assembly instruction.

The correct inline assembly syntax to trigger a breakpoint interrupt is __asm__("int3").

4fill in blank

hard

Complete the code to create a macro that triggers a breakpoint.

Embedded C

#define BREAKPOINT() __asm__ [1] ;

void main() {
    BREAKPOINT();
}

Drag options to blanks, or click blank then click option'

A("int3")

B("trap")

C;

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong assembly instructions or missing the semicolon.

Using colon instead of semicolon at the end.

The macro uses __asm__("int3"); to trigger a breakpoint with proper syntax.

5fill in blank

hard

Fill all three blanks to write a function that sets a breakpoint and increments a volatile counter.

Embedded C

volatile int [1] = 0;

void set_breakpoint() {
    __asm__[2];
    [3]++;
}

Drag options to blanks, or click blank then click option'

Adebug_counter

B("int3")

D("break")

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in declaration and increment.

Using wrong assembly instructions.

The function uses a volatile variable named debug_counter and triggers a breakpoint with __asm__("int3");.

Practice

1. What is the main purpose of setting a breakpoint in embedded C programming?

easy

A. To pause the program at a specific line to inspect variables and flow

B. To speed up the program execution

C. To permanently stop the program from running

D. To automatically fix errors in the code

Solution

1. Step 1: Understand what a breakpoint does

   A breakpoint pauses the program at a chosen line during debugging to check the program state.

2. Step 2: Identify the correct purpose

   Only To pause the program at a specific line to inspect variables and flow describes pausing to inspect variables and flow, which is the main use of breakpoints.

3. Final Answer:

   To pause the program at a specific line to inspect variables and flow -> Option A

4. Quick Check:

   Breakpoint = Pause and inspect [OK]

Hint: Breakpoints pause code to check variables and flow [OK]

Common Mistakes:

• Thinking breakpoints speed up code
• Confusing breakpoints with program termination
• Assuming breakpoints fix errors automatically

2. Which of the following is the correct way to set a breakpoint in an embedded C debugger?

easy

A. Write breakpoint(); in the code to set a breakpoint

B. Use the command break main.c:25 to set a breakpoint at line 25

C. Add #breakpoint 25 in the source code

D. Use set breakpoint 25 inside the C code

Solution

1. Step 1: Recognize debugger commands

   Debugger commands like break filename:line set breakpoints externally, not inside code.

2. Step 2: Identify correct syntax

   Use the command break main.c:25 to set a breakpoint at line 25 uses the correct debugger command format to set a breakpoint at line 25 in main.c.

3. Final Answer:

   Use the command break main.c:25 to set a breakpoint at line 25 -> Option B

4. Quick Check:

   Debugger command syntax = break filename:line [OK]

Hint: Use debugger commands, not code, to set breakpoints [OK]

Common Mistakes:

• Trying to set breakpoints by adding code lines
• Using incorrect syntax inside source code
• Confusing preprocessor directives with breakpoints

3. Given the following code snippet and a breakpoint set at line 5, what will the debugger do when running the program?

1: int main() {
2:   int x = 10;
3:   int y = 20;
4:   int z = x + y;
5:   z = z * 2;  // Breakpoint here
6:   return z;
7: }

medium

A. Ignore the breakpoint and run normally

B. Pause execution after line 5 executes

C. Pause execution at line 6

D. Pause execution before line 5 executes

Solution

1. Step 1: Understand breakpoint behavior

   A breakpoint pauses execution just before the specified line runs, allowing inspection before the line executes.

2. Step 2: Apply to given code

   Breakpoint at line 5 pauses before z = z * 2; runs, so execution stops right before line 5.

3. Final Answer:

   Pause execution before line 5 executes -> Option D

4. Quick Check:

   Breakpoint pauses before line runs [OK]

Hint: Breakpoints pause before the line executes [OK]

Common Mistakes:

• Thinking breakpoint pauses after line executes
• Assuming breakpoint pauses at next line
• Believing breakpoint is ignored if code is simple

4. You set a breakpoint at line 10 in your embedded C program, but the debugger never stops there. What is the most likely reason?

medium

A. The debugger does not support breakpoints

B. The breakpoint command syntax was incorrect

C. The program never reaches line 10 during execution

D. Breakpoints only work on function entry lines

Solution

1. Step 1: Consider program flow

   If the program never executes line 10, the breakpoint there will never be hit.

2. Step 2: Evaluate other options

   Debugger usually supports breakpoints and syntax errors cause errors; breakpoints work on any line, so The program never reaches line 10 during execution is most likely.

3. Final Answer:

   The program never reaches line 10 during execution -> Option C

4. Quick Check:

   Breakpoint hit only if line runs [OK]

Hint: Breakpoint triggers only if code line runs during execution [OK]

Common Mistakes:

• Assuming debugger lacks breakpoint support
• Believing breakpoints only work on function starts
• Ignoring program flow and conditions

5. You want to debug a function that is called multiple times in a loop. How can you set breakpoints to pause only on the third call of the function in embedded C?

hard

A. Set a conditional breakpoint that triggers when a call counter equals 3

B. Set three breakpoints at the function start line

C. Set a breakpoint outside the function before the loop

D. Set a breakpoint at the function end line

Solution

1. Step 1: Understand conditional breakpoints

   Conditional breakpoints pause execution only when a condition is true, such as a counter reaching 3.

2. Step 2: Apply to multiple calls

   Using a call counter variable and setting a breakpoint with condition (counter == 3) pauses only on the third call.

3. Step 3: Evaluate other options

   Setting multiple breakpoints or breakpoints outside function won't selectively pause on the third call.

4. Final Answer:

   Set a conditional breakpoint that triggers when a call counter equals 3 -> Option A

5. Quick Check:

   Conditional breakpoint = pause on specific call [OK]

Hint: Use conditional breakpoints with counters to target specific calls [OK]

Common Mistakes:

• Setting multiple breakpoints instead of one conditional
• Placing breakpoints outside the function
• Not using a counter to track calls