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Introduction to the GNU Debugger GDB and Debugging Techniques
What is GDB?
GDB, short for GNU Debugger, is a powerful command-line tool used for debugging programs written in different programming languages, such as C, C++, and Fortran. It allows programmers to track and rectify errors, investigate program behavior, and analyze the flow of code execution. GDB provides various features for examining memory, setting breakpoints, stepping through code, and interacting with programs currently running or stopped. It is a valuable tool for developers to diagnose and fix issues in their code.
Getting Started with GDB
To begin using GDB, it is essential to have a compiled executable file of your program along with the debugging symbols. Debugging symbols contain additional information about your code, such as variable names, line numbers, and function names, which makes it easier for GDB to interpret and provide meaningful information during debugging.
Once you have the necessary files, open a terminal and type the command:
gdb executable-file
Replace “executable-file” with the name of your executable file. This command starts the GDB debugging session with your program.
Basic Debugging Techniques
1. Setting Breakpoints: Breakpoints allow you to pause the execution of your program at a specific line or function, allowing you to inspect the state of your program at that point. To set a breakpoint at a particular line, use the command:
break line-number
Replace “line-number” with the line number where you want to set the breakpoint. GDB will pause the program when it reaches that line.
2. Stepping Through Code: Once the program is paused at a breakpoint, you can step through the code line by line to analyze how it behaves. Use the following commands:
– next (or n): Executes the next line of code.
– step (or s): Steps into function calls, allowing you to trace the flow of the code more detailed.
– finish: Runs the program until the current function is completed.
3. Examining Variables: GDB enables you to inspect the values of variables during runtime. Use the command:
print variable-name
Replace “variable-name” with the name of the variable you want to examine. GDB will display its current value.
4. Backtracing: When an error occurs, GDB can provide a backtrace, showing the sequence of function calls leading to the error. This can be helpful in understanding how the program ended up in its current state. Use the command:
bt
This will display the backtrace information.
These are just the basics of GDB, but the tool offers many more advanced features, such as watchpoints, memory examination, attaching to running processes, and more. Exploring the GDB documentation and experimenting with various commands will help you become more proficient in debugging your programs.
Remember, the key to successful debugging is approaching it in a systematic manner, using the available debugging techniques, and being patient and persistent in finding and resolving issues in your code.
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