Debugging

21/04/23

Debugging

21/04/23

Debugging

Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a program or a piece of electronic hardware.

It is the most important activity in the software and program development.

It is used in order to remove or identify logical errors in the program.

Debugging is not testing but testing can be a part of debugging. Testing finds errors; debugging localizes and repairs them.

Debugging is a black art.

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Debugging

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What is a Debugger?

“A software tool that is used to detect the source of program or script errors, by performing step-by-step execution of application code and viewing the content of code variables.”

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Debugging

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Why Debug?

When your program crashes Finding out where it crashed Examining program memory at that point

When a bug occurs in your program Watching program variables Identifying where the problem occurs (and

why) Tracing through a program

Learning what a program does Good basic testing approach

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Debugging

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Steps in Debugging Process

1. Compile your program(s) enabling the same for Debugging. i.e. gcc –g –o p prg.c

2. Execute the debugger3. Run the program as you normally would.

When the error occurs, Debugger will provide information regarding the location of the error, and possible reasons for its occurrence. (It also provides more detail about the error than the initial error messages you may have received without using the debugger)

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Debugging

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Debuggers

Command-line debuggers : gdb (C, C++), jdb (java), “perl –d”

DDD – Data Display Debugger – Linux Debugger

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Debugging

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GDB

Compile with the "-g" option (for most GNU and Intel compilers) which generates added information in the object code so the debugger can match a line of source code with the step of execution.gcc -g eg.c -o eg

Running gdb gdb name-of-executable (gbd ./eg)

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Debugging

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When gdb is started, it should look somewhat like this:GNU gdb 2002-08-18-cvsCopyright 2002 Free Software Foundation, Inc.GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions.Type "show copying" to see the conditions.There is absolutely no warranty for GDB. Type "show warranty" for details.This GDB was configured as "powerpc-linux".(gdb)

(gdb) quit

(gdb) list

(gdb) run

(gdb) print x

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Debugging

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Breakpoints

gdb returns control back to you when it reaches that exact point.

Breakpoints are created using the break command. For instance, this is telling gdb to pass back control on line 19 and 21:

RUNNING NAVIGATION(gdb) next

(gdb) step

(gdb) continue

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Debugging

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GDB Breakpoints

• Useful breakpoint commands:b[reak] [<where>] sets breakpoints. <where> can be

a number of things, including a hex

address, a function name, a line

number, or a relative line offset[r]watch <expr> sets a watchpoint, which will break

when <expr> is written to [or read]info break[points] prints out a listing of all breakpointsclear [<where>] clears a breakpoint at <where>d[elete] [<nums>] deletes breakpoints by number

DDD: Best Visual Debugger

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Debugging

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Starting DDD

Open your executable program in DDD ddd ./eg OR ddd ./a.out

(sudo apt-get install ddd)

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Debugging

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Debugger Console and Data Window

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Set Breakpoint

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