How do you handle errors in C?

In C, errors can be handled using various techniques and mechanisms. Error handling in C typically involves detecting errors and taking appropriate actions to handle or report them. Here are some common methods for error handling in C:

• 1. Return Values:
• Functions can return special values or error codes to indicate that an error has occurred. The calling code can check these return values and take appropriate actions.
• For example, many standard library functions return -1 or NULL to indicate errors, and the specific error code can be retrieved using the errno variable.

int result = some_function();

if (result == -1) {

    perror("Error in some_function");

}

2. errno and perror:

• The errno variable is a global integer variable that is set by certain library functions when an error occurs. You can use perror to print a descriptive error message based on the value of errno.

if (some_function() == -1) {

    perror("Error in some_function");

}

3. Custom Error Codes:

• You can define your own error codes using #define or enum and return these codes from your functions to indicate specific errors.

#define FILE_NOT_FOUND 1

#define MEMORY_ALLOCATION_ERROR 2

int custom_function() {

    if (some_condition) {

        return FILE_NOT_FOUND;

    }

    // ...

}

4. Error Handling Functions:

• You can create custom error-handling functions that encapsulate error reporting and recovery logic. These functions can be called when an error occurs.

void handle_error(int error_code) {

    switch (error_code) {

        case FILE_NOT_FOUND:

            fprintf(stderr, "File not found.\n");

            break;

        case MEMORY_ALLOCATION_ERROR:

            fprintf(stderr, "Memory allocation failed.\n");

            break;

        // Handle other error codes...

    }

}

5. setjmp and longjmp:

• These functions provide a way to implement non-local error handling by setting a "jump" point in your code where you can return to in case of an error.

#include <setjmp.h>

jmp_buf jump_buffer;

int main() {

    if (setjmp(jump_buffer) != 0) {

        // Handle error here

        fprintf(stderr, "An error occurred.\n");

    } else {

        // Normal code execution

        // ...

        // Setjmp point

        longjmp(jump_buffer, 1); // Jump to the error handling code

    }

    return 0;

}

• 6. Resource Cleanup:
• When dealing with resources like files or memory, it's essential to release them properly in case of an error using techniques like fclose or free to prevent resource leaks.

Error handling in C often requires careful consideration of memory management, resource cleanup, and choosing the appropriate approach depending on the specific requirements of your program.