What is GDB?
GDB, or GNU Debugger, is a powerful command-line debugger available for various operating systems, including Linux. It allows developers to analyze and debug programs written in languages such as C, C++, and other supported languages. GDB enables users to track down bugs, analyze memory usage, and understand program execution flow by providing tools for inspection and control of running programs.
Basic Syntax
To start debugging with GDB, you need to compile your code with debugging symbols enabled. For example, if you are compiling a C program with gcc, you would include the -g flag:
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gcc -g my_program.c -o my_program
To start debugging your program, you would run GDB followed by the name of the executable:
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gdb my_program
Once inside GDB, you can set breakpoints, examine variables, and step through the program’s execution using commands like break, run, info variables, next, and print.
Example Codes
Here are three example codes to demonstrate how GDB can be used to debug programs:
- Setting a breakpoint: ```c #include
int main() { int x = 10; printf(“Before breakpoint\n”); x = x * 2; printf(“After breakpoint\n”); return 0; }
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Run GDB with the compiled executable and set a breakpoint at line 6 before running the program. When the program execution reaches the breakpoint, you can inspect the variable `x`.
2. Stepping through the program:
```c
#include <stdio.h>
int sum(int a, int b) {
return a + b;
}
int main() {
int x = 10;
int y = 20;
int result = sum(x, y);
printf("Result: %d\n", result);
return 0;
}
By using commands like next and step, you can step through the execution of the program to understand how the sum function is called and the result is computed.
- Examining memory: ```c #include
#include
int main() { int* nums = (int*)malloc(5 * sizeof(int)); for(int i = 0; i < 5; i++) { nums[i] = i * 10; } free(nums); return 0; } ``` You can use GDB to analyze memory usage, set watchpoints, and debug memory-related issues like memory leaks and segmentation faults.
Applicable Versions
GDB is constantly evolving, and newer versions may offer additional features and enhancements. The basic usage and commands are consistent across versions, but it’s recommended to use the latest stable release for optimal functionality.
By mastering GDB, developers can efficiently debug programs, identify problems, and improve code quality in their Linux projects. Whether you are a beginner or an experienced developer, understanding how to utilize GDB can significantly enhance your debugging skills.