Generated C code inspection in Simulink - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple generated C function

What is the output of the following generated C code snippet when input = 5?

Simulink

int generated_function(int input) {
    int output = 0;
    for (int i = 0; i < input; i++) {
        output += i * 2;
    }
    return output;
}

int main() {
    int result = generated_function(5);
    printf("%d", result);
    return 0;
}

A 20

B 30

C 40

D 50

💡 Hint

Sum the values of i*2 for i from 0 to 4.

The loop runs from i=0 to i=4. The sum is 0*2 + 1*2 + 2*2 + 3*2 + 4*2 = 0 + 2 + 4 + 6 + 8 = 20.

❓ data_output

intermediate

Inspecting array output from generated code

What is the content of the array output after running this generated C code?

Simulink

void generated_array(int input, int output[]) {
    for (int i = 0; i < input; i++) {
        output[i] = i * i;
    }
}

int main() {
    int output[4];
    generated_array(4, output);
    for (int i = 0; i < 4; i++) {
        printf("%d ", output[i]);
    }
    return 0;
}

A 1 4 9 16

B 0 2 4 6

C 0 1 4 9

D 0 1 2 3

💡 Hint

Each element is the square of its index.

The loop assigns output[i] = i*i for i from 0 to 3, so output is [0,1,4,9].

🔧 Debug

advanced

Identify the error in generated C code snippet

What error will this generated C code produce when compiled?

Simulink

int generated_error(int input) {
    int output;
    if (input > 0)
        output = input * 2;
    return output;
}

int main() {
    int result = generated_error(0);
    printf("%d", result);
    return 0;
}

A No error, prints 0

B Syntax error: missing semicolon

C Type error: incompatible types

D Use of uninitialized variable 'output'

💡 Hint

Consider what happens when input is 0.

If input is 0, output is never assigned a value but is returned, causing use of uninitialized variable.

🧠 Conceptual

advanced

Understanding memory layout in generated C code

In generated C code, which memory segment typically stores global variables?

A Data segment

B Stack segment

C Heap segment

D Code segment

💡 Hint

Globals are stored separately from local variables and dynamic memory.

Global variables are stored in the data segment, which is separate from stack and heap.

🚀 Application

expert

Analyzing performance impact of generated C code loop unrolling

Given this generated C code with loop unrolling, what is the main benefit compared to a simple loop?

Simulink

void generated_unrolled(int *arr, int n) {
    for (int i = 0; i < n; i += 4) {
        arr[i] = arr[i] * 2;
        arr[i+1] = arr[i+1] * 2;
        arr[i+2] = arr[i+2] * 2;
        arr[i+3] = arr[i+3] * 2;
    }
}

A Automatically parallelizes code across multiple CPU cores

B Reduces loop overhead and increases instruction-level parallelism

C Decreases code size significantly

D Eliminates the need for array bounds checking

💡 Hint

Think about how fewer loop iterations affect CPU instructions.

Loop unrolling reduces the number of loop control instructions and allows the CPU to execute multiple instructions simultaneously.