How to Debug C Code in a Visual Studio

Feb. 9, 2017 | smlee36 | #seneca, #c, #beginner, #visualstudio, #debug, #Abdi

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This is an ultra simple tutorial for debugging c program in a Visual Studio.

TOC

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Case Study

Sample Program

• Run Visual Studio and Open your progect. If you don't know how to make a project, read this post first.

• A program instruction is here.

  • input number between 1 ~ 10
  • If input number is invalid (out of range), print a error message and input again until the number is valid.

• this is a sample code for the instruction.

// An ultra simple debugging example

#include <stdio.h>

int main() {
    
    int num;

    printf("Enter your number (1-10): ");
    scanf("%d", &num);

    while (num < 1 || 10 < num) {
        printf("Input number should be 1 - 10.");

        printf("Enter your number again (1-10): ");


    }

    printf("Your number is %d.\n", num);


    return 0;
}

• Now run 'DEBUG > Start without debuging' (Ctrl + F5), the program. The 'Enter your number (1-10): ' message is displayed on the center-bottom pane. Enter '5' . Then the program will be end normally.

• Now run the program again. Enter '11' . The program shows an error message continuously.

Debug the Program

Marking break points

• First of all, select some position. If you don't know where you should choose, select the first line (line 7). Press a RIGHT MOUSE BUTTON at the variable on line 7. Choose 'Insert Breakpoint', then a red break point mark will be shown.

• Now run 'DEBUG > Start with debuging' (Ctrl + F5) the program. Enter an invalid number '11' . Then a yellow current position arrow will be displayed at line 7. It is a marker to indicate in where C compiler is doing it's job now.
• Press 'F11'(Step into) then the process marker will proceed line by line.
• When the process marker locate at 'Enter your number again' message, the marker will go back to the beginning of while loop instead of going line 18.

• So, we can realize something is needed after line 13 to stop infinite loop.

• Insert this statement into after line 14.

scanf("%d", &num);

As described above, developer can see the exact position of compiler in progress.

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