Skip to main content

The Basics of GDB


To start GDB, in the terminal,

gdb <executable name>
For the above example with a program named main, the command becomes
gdb main
Setting Breakpoints

You'll probably want you program to stop at some point so that you can review the condition of your program. The line at which you want the program to temporarily stop is called the breakpoint.

break <source code line number>
Running your program

To run your program, the command is, as you guessed,

run

Looking at the code

When the program is stopped, you can do a number of important things, but most importantly you need to see which part of the code you've stopped. The command for this purpose is "list". It shows you the neighbouring 10 lines of code.

Next and Step

Just starting and stopping isn't much of a control. GDB also lets you to run the program line-by-line by the commands 'next' and 'step'. There is a little difference between the two, though. Next keeps the control strictly in the current scope whereas step follows the execution through function calls.

Look at this example carefully;

Suppose you have a line in the code like


value=display();
readinput();

If you use the next command, the line (and the function, provided there aren't breakpoints in it) gets executed and the control advances to the next line, readinput(), where you can perhaps examine 'value' to get an idea of how display() worked.

But if you use the step command, you get to follow what display() does directly, and the control advances to the first line of display(), wherever it is.

Posted By :-Cplusplusprogramming

Popular posts from this blog

Putimage function in c

putimage function outputs a bit image onto the screen. Declaration:- void putimage(int left, int top, void *ptr, int op); putimage puts the bit image previously saved with getimage back onto the screen, with the upper left corner of the image placed at (left, top). ptr points to the area in memory where the source image is stored. The op argument specifies a operator that controls how the color for each destination pixel on screen is computed, based on pixel already on screen and the corresponding source pixel in memory. c smiling face animation This animation using c draws a smiling face which appears at random position on screen. See output below the code, it will help you in understanding the code easily. C programming code #include<graphics.h> #include<conio.h> #include<stdlib.h>   main() { int gd = DETECT, gm, area, temp1, temp2, left = 25, top = 75; void *p;   initgraph(&gd,&gm,"C:\\TC\\BGI");   setcolor(YELLOW)...
Read more

What are selection statements in C++ ? If and Switch

There are several statements that we can use in C++ programming that help in choosing a set of instructions for using the code depending upon an expression truth value.  What are Selection Statements in C++? As mentioned above there are several statements that we can use to choose a set of pre-defined instructions within a program in any section of the program as per the need. These are called selection statements in C++  In C++ Program there are two types of Selection statements  1. If  2. Switch  The If Statement of C++ To understand "if statement" let's look at an example.  Example - If you have 10 rupees then you can buy the chocolate.  Here, there is a condition in buying chocolate, if you have 10 rupees then only you can buy it.  This shows that the If is a condition which can be true or false, If it is false it won't be executed, in this example, if you don't have 10 rupees i.e. the condition is false you cant buy the chocolate.  So, I...
Read more

What are the characteristics of a good program in C++

The program should be written in a good style so that it is understandable to a reader. A good program is efficient in solving the given program.  Here are some of the characteristics of a good program : Effective and Efficient  User Friendly  Self-Documenting Code  Reliable  Portable  I.  Effective and Efficient The program produces correct results and works faster, taking into account of the memory constraints.  II.  User Friendly The user should not be concerned about inside the program, a program should work with the user by understandable messages and user work should be very low. The user should only be responsible to provide input the rest of the program should do.  III.  Self-Documenting Code A good program must be self-documented. The source code uses meaningful names for variables, subprograms and other constants.  IV.  Reliable The program must be able to handle unexpected situations like wrong data or no data,...
Read more