What exactly is a bug?
As per the findings of Ko and Meyers (2004), a software bug occurs when there is a discrepancy between the intended software design and its actual implementation, leading to unexpected outcomes.
Examples:
- Anticipated result for factorial(5) was 120, however it returned 0.
- Expected the program to complete without errors, but it terminated abruptly with a "segmentation fault" message.
Types of Bugs
There are various types of bugs, including:
- Compile-time errors: These arises during the compiler's compilation process whenever the code breaches syntax rules . Missing semicolons, undefined variables, and typos are a few examples.
- Runtime Errors: These errors occur when the program is running. Division by zero, null pointer dereference, and overflowing buffers are common.
- Errors in Logic: Debugging logic flaws is the most difficult. They occur when the program's logic is wrong, resulting in inaccurate results or unexpected behaviour.
- Concurrency Issues: Debugging concurrency-related difficulties such as race situations and deadlocks in multiple-threaded or multi-process programs is difficult.
Debugging Methods
There are several methods for debugging . Some main methods for debugging are as follows:
- Print Statements: Inserting print statements into the code for displaying the values of variables, calls to function, and control flows is one of the easiest debugging approaches. It allows you to follow the program's execution.
- Interactive Debuggers: Debugging programs are specialized tools that allow a more systematic and collaborative approach to troubleshooting. GDB (GNU Debugger) is a popular C debugging tool. You can use it to set breakpoints, analyze variables, and walk through code.
- Static Testing Tools: Tools like lint or static analyzers may identify possible mistakes without running the code. They can detect a wide range of common code errors.
- Dynamic Analysis Tools: Dynamic analysis tools, such as storage profilers and sanitisers (e.g., AddressSanitizer), enable the detection of memory leaks, overflows of buffers, and other execution issues.
Debugging is usually done systematically:
- Reproduce the Issue: Begin by comprehending the issue. Continuously reproduce the issue to comprehend the issue's scale and impact.
- Identify the Issue: Determine the exact section of code where the problem occurs. Examining error message logs or utilizing a debugger is frequently required.
- Determine the Root Cause: Determine the root cause when you've isolated the problem. It could be a logical error, bad data, or an improper function call.
- Resolve the Problem: Create a solution to the bug. Check that the solution solves the root problem and does not bring new problems.
- Test the correction: Once the correction has been implemented, extensively test the code to ensure the issue has been handled. It could include executing unit, integration, or user tests.
- Regression Testing: Exercise caution while introducing new bugs and addressing existing ones. Regression testing should be performed to guarantee that existing functionality is not lost.
- Documentation: Write out the bug, how it was fixed, and any lessons learned. This helps in the exchange of information and the prevention of similar problems in the future.
Tips and Best Practices for Debugging
There are several tips and best practices for debugging . Some main tips and best practices for debugging are as follows:
- Use Version Control: Versioning systems such as Git help monitor changes, making it easier to determine when an issue was introduced.
- Divide and Conquer: When facing complex issues, break the issue into numerous smaller elements.
- Read Documentation: To obtain a greater understanding of libraries and APIs, read documentation, instructional materials, and error messages.
- Code Reviews: Peer evaluations of code can detect bugs early and provide helpful ideas.
- Remain Calm: Debugging can be exhausting. Stay cautious, take breaks, and avoid making quick changes that may bring new problems.
- Test Environment: Ensuring your test and development platforms are as near to the production environments as possible.
Tools for Debugging
There are several tools for debugging . Some main tools for debugging are as follows:
- GDB (GNU Debugger): GDB is a strong C and C++ command-line debugger. You can use it to set breakpoints, click inspect variables, and regulate program execution.
- Valgrind: Valgrind is a toolset containing memory evaluation instruments, such as Memcheck, that can aid in detecting memory-related issues.
- AddressSanitizer: During the runtime, this tool assists in identifying memory-related issues such as overflows of buffers and use-after-free errors.
- Integrated Development Environments (IDEs): IDEs such as Visual Studio, CLion , and Code::Troubleshooting capabilities are built into blocks, which include graphical interfaces.
- Static Analyzers: Tools such as cppcheck and Clang Static Analyzer can detect potential bugs in programs without running them.
Debugging is an essential competency for a developer, and gaining experience from practical scenarios can be highly advantageous. Below are some C programming illustrations showcasing common debugging scenarios along with detailed clarifications:
1. Null Pointer Dereference:
Let's consider a program demonstrating the null pointer dereference issue in the C programming language.
#include <stdio.h>
int main() {
int* pt = NULL;
*pt = 100; // Dereferencing a null pointer, causing a segmentation fault
printf("This won't be reached.\n");
return 0;
}
Output:
Segmentation fault (core dumped)
Issue: The program tries to access a memory location using a null pointer, leading to a segmentation fault.
Debugging: Utilizing a debugger such as GDB will accurately identify the line where a segmentation fault occurs. The backtrace command (bt) is helpful for examining the call stack, while the print command (p) can assist in scrutinizing variables.
2. Array index out of Bounds
Let's consider a program to demonstrate the array index out of bounds error in the C programming language.
#include <stdio.h>
int main() {
int array[5] = {10, 20, 30, 40, 50};
printf("%d\n", array[10]); // Accessing an out-of-bounds array index
return 0;
}
Output:
1989877136
Issues: The code is attempting to retrieve a value from an array index that is beyond its bounds, resulting in an out-of-bounds error.
Debugging: Utilizing debugging tools is crucial for identifying the specific line causing issues. Employ the print (or p) function to inspect the contents of the variable arr and understand the reason behind the index exceeding its bounds.
3. Infinite loop
Let's consider a program to demonstrate infinite loops in the C programming language.
#include <stdio.h>
int main() {
int ind= 0;
while (ind >= 0) {
printf("Iteration %d\n", ind);
ind++; // Forgetting to increment the loop control variable
}
return 0;
}
Output:
Iteration 51359
Iteration 51360
Iteration 51361
Iteration 51362
Iteration 51363
Iteration 51364
Iteration 51365
Iteration 51366
Iteration 51367
Iteration 51368
Iteration 51369
Iteration 51370
Iteration 51371
Iteration 51372
Iteration...
Problem: The loop gets stuck in an infinite cycle due to the loop control variable i nd consistently being greater than or equal to zero.
Debugging: Place breakpoints in the code and inspect the value of "ind" using a debugger. Upon examination, you will observe that the variable "ind" does not decrease, leading to an infinite loop.
4. Logic Error
Let's analyze a program to demonstrate a logic flaw in the C language.
#include <stdio.h>
int main() {
int m = 5;
int n = 10;
if (m > n) {
printf("m is greater than n.\n");
} else {
printf("m is not greater than n.\n");
}
return 0;
}
Output:
m is not greater than n.
There is an error in the code where it incorrectly states that "m is not greater than n" even when it actually is.
Troubleshooting: No runtime problems exist in this scenario. Troubleshooting includes analyzing the logic and comparing it to the expected behavior to pinpoint and correct errors.