CodeBhavya

C PROGRAMMING PROGRAM • FUNCTIONS, PREPROCESSOR & COMMAND LINE

Use Conditional Compilation for Debug Output

Learn how to use conditional compilation for debug output using a clear C program.

Intermediate#ifdefCompile-time flagDebug build

PROBLEM UNDERSTANDING

Input and expected output

Sample input
No input required
Sample output
Debug: result was calculated.
Result = 42

COMPLETE C PROGRAM

Complete C implementation

conditional-compilation.c
Open in compiler
#include <stdio.h>

#define DEBUG_MODE

int main(void)
{
    int result = 7 * 6;
#ifdef DEBUG_MODE
    printf("Debug: result was calculated.\n");
#endif
    printf("Result = %d\n", result);
    return 0;
}

GUIDED CODE TOUR • NOT LIVE EXECUTION

Study the program line by line

Use the real compiler button above to run and debug with different inputs.

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Debug: result was calculated.
Result = 42
0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

  1. Read the required input values.
  2. Define a compile-time symbol and include diagnostic statements only while that symbol exists.
  3. Display the computed result.

Define a compile-time symbol and include diagnostic statements only while that symbol exists.

EFFICIENCY

Time and space complexity

Time complexity

O(1)

Auxiliary space

O(1)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.