Unit 8 Compiling C/C++ Code Debugging Programs 2 COMPILATION 3 - - PowerPoint PPT Presentation

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Unit 8

Compiling C/C++ Code Debugging Programs

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COMPILATION

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Editors

• "Real" developers use editors

designed for writing code

– No word processors!!

• You need a text editor to

write your code

– Eclipse, Sublime, MS Visual Code, Emacs, Atom, and many others

• These often have handy functions for

commenting, indenting, checking matching braces ({..}) etc.

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Compilers

• Several free and commercial compilers are

available

– g++: – clang++ – XCode – MS Visual Studio

• Several have "integrated" editors, debuggers

and other tools and thus are called IDE's (Integrated Development Environments)

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Using the Command Line

• While GUIs are nice, we often have

more control when using the command line interface (i.e. the terminal)

• Linux (the OS used by Vocareum and in

CS 103, 104, etc.) has a rich set of command line utilities (Mac & Windows do to though Windows uses different names for the utilities)

• We can navigate the file system (like you

would with Explorer or Finder), start programs (double-clicking an icon), and much more by simply typing commands

Terminal Icon Linux Terminal View Vocareum Terminal View

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Software Process

Executable Binary Image ("test")

1110 0010 0101 1001 0110 1011 0000 1100 0100 1101 0111 1111 1010 1100 0010 1011 0001 0110 0011 1000

C++ file(s) (test.cpp) Compiler

#include <iostream> using namespace std; int main() { int x = 5; cout << "Hello" << endl; cout << "x=" << x; return 0; }

g++ Load & Execute

$ subl test.cpp & $ subl test.cpp & $ g++ –g –Wall test.cpp –o test

• r

$ make test $ subl test.cpp & $ g++ –g –Wall test.cpp –o test $ ./test

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Compile & fix compiler errors

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Edit & write code

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Load & run the executable program

Std C++ & Other Libraries

Note: Most documentation and books use $ as a placeholder for the command line prompt. Input file (source code) Output file (binary executable)

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g++ Options

• Most basic usage

– g++ cpp_filenames – Creates an executable a.out

• Options

– -o => Specifies output executable name (other than default a.out) – -g => Include info needed by debuggers like gdb, kdbg, etc. – -Wall => show all warnings

• Most common usage form:

– $ g++ -g -Wall hw8.cpp -o hw8

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Listing Files (Folder Contents)

• In Mac/Linux, to view the files in a folder, just

type ls (stands for list)

Executable Source code file

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Running the Program

• First ensure the program compiles

– $ g++ -g -Wall hw8.cpp -o hw8

• Then run the program by preceding the

executable name with ./

– $ ./hw8

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DEBUGGING – PART 1

(Part 2 in a few weeks)

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Bugs

• The original "bug"

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Step 1: Review your Own Code

• Rubber Duck Debugging: Reference from an

anecdote from a book, "The Pragmatic Programmer", that has become popular

• Idea: Explain your code line by line to yourself or

some other "object"

– Note: Commenting your code is a way to do this

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Step 2: Test Cases & Expected Outputs

• Determine input test case(s) that will exercise

various parts of your code

– Each if/else block – When the loop executes 0, 1, or more times

• Determine the expected output

– You cannot effectively debug without an expectation of the right output so you know when the program is working

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Step 3: Tracing

• Use one of your input

scenarios that is not working and trace the execution of your code by hand

– Make a table of variables and walk the code line by line

#include <iostream> using namespace std; int main() { int ones=0, tens=0; int num; while(ones != 2 || tens != 2){ cout << "Enter a num: " << endl; cin >> num; if(num < 10){

• nes++;

} else { tens++; } if(num < 0){ break; } } cout << "ones: " << ones; cout << " tens: " << tens << endl; return 0; }

• nes

tens num

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Step 4: Print Statements / Narration

• Now that you know what to expect, the

most common and easy way is to find the error is to add print statements that will "narrate" where you are and what the variable values are

• Be a detective by narrowing down where

the error is

– Put a print statement in each 'for', 'while', 'if'

• r 'else' block…this will make sure you are

getting to the expected areas of your code – Then print variable values so you can see what data your program is producing

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Tips

• Don't write the entire program all at once
• Write a small portion, compile and test it

– Write the code to get the input values, add some couts to print out what you got from the user, and make sure it is what you expect – Write a single loop and test it before doing nested loops

• Once one part works, add another part and

test it

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Vocareum Exercises 1

• diff1

– Count how many consecutive values differ by 1

• atleast2

– Input numbers until we have at least 2 from the range 0-9 and >=10 but stop immediately if the user enters a negative number

• craps

– 1. The player rolls 2 dice. – 2. If the sum of the dice is 7 or 11 the player wins their bet and the turn continues (go back to step 1). – 3. If the sum of the dice is 2, 3, or 12 the player loses their bet, but the turn continues (go back to step 1). – 4. If the sum is any other number (besides 2, 3, 7, 11, or 12) then that value is known as the point number and play continues. – 5. The player rolls the dice until...

• a. The sum of the dice is 7 in which case the player loses their bet and the turn ENDS
• b. The sum of the dice is the same as the point value in which case the player wins their bet

and the turn continues, starting over at step 1.

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LINUX AND NAVIGATING FILE SYSTEMS

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Linux

• Based on the Unix operating system
• Developed as an open-source ("free") alternative by

Linux Torvalds and several others starting in 1991

• Originally only for Intel based processors but has

now been ported to other platforms (i.e. ARM processors in your phone, etc.)

• Commonly used in industry and in embedded

devices

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Using the Command Line

• While it has a GUI interface like

your Mac or Windows PC much

• f its power lies in its rich set of

utilities that are most easily run at the command line (aka command prompt or terminal)

• Here we can navigate the file system

(like you would with Explorer or Finder), start programs (double- clicking an icon), and much more by simply typing commands

Terminal Icon Linux Terminal View Vocareum Terminal View

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Navigating the File System

• A file system has

– Folders (directories) – Files

• They are organized in a hierarchy
• Everything we can do with a GUI we can do at the command line

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Some Basic Commands

• Here are some helpful commands to use in

Linux at the command prompt

Command ls List (see) all files in the current folder pwd Present working directory shows the current folder location of the terminal cd dirname Change directory to a new folder cp srcfiles dest Copy file(s) to a new location mv srcfile dest Move/rename files to a new name/location rm srcfiles Remove files from the current folder mkdir dirname Make directory / create a new folder rmdir dirname Remove directory / delete a folder (must be empty first)

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Directory Structure Ex. 1

• Each circle is a directory
• Each name in the box is a file
• Starting from your home (e.g.

'mark') directory/folder…

• Use cd to change directories

(folders)

– cd Desktop – cd cs102 – cd hw7

• Or go multiple folders at a

time

– cd Desktop/cs102/hw7 mark

Desktop

hw7

Documents

• ther

src

hw7a.cpp hw7b.cpp test2.h test2.cpp

cs102

you start here

home /

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Directory Structure Ex. 2

• To go up a level use

– cd ..

• To go up 2 levels use

– cd ../..

• Let's go one level to 'cs102'

– cd ..

• Now make a directory

– mkdir hw8

mark

Desktop

hw7

Documents

• ther

src

hw7a.cpp hw7b.cpp test2.h test2.cpp

home cs102

you start here

hw8

Shortcuts: . = Current directory .. = Parent directory (up one) ~ = Home directory * = Wildcard to match filenames Unix commands: pwd = Print current working dir

/

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Directory Structure Ex. 3

• Let's say we want to start a

new lab with a copy of our

• ld work and just modify it.

Let's copy our work – Recall I'm in cs102 folder currently

– cp hw7/* hw8/ mark

Desktop

hw7

Documents

• ther

src

hw7a.cpp hw7b.cpp test2.h test2.cpp

cs102

you start here

hw8 home /

hw7a.cpp hw7b.cpp Shortcuts: . = Current directory .. = Parent directory (up one) ~ = Home directory * = Wildcard to match filenames Unix commands: pwd = Print current working dir

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Directory Structure Ex. 4

• Let's now go into the test

folder

– cd test

• Now rename the hw7a.cpp to

hw8.cpp

– mv hw7a.cpp hw8.cpp

• Now delete the hw7b.cpp file

– rm hw7b.cpp

• Remember, you can see all the

files in a folder by typing

– ls

• You can see what

folder/directory you are in by typing

– pwd

mark

Desktop

hw7

Documents

• ther

src

hw7a.cpp hw7b.cpp test2.h test2.cpp

cs102

you start here

hw8 home /

hw7a.cpp hw7b.cpp