Programsystemkonstruktion med C++: Övning 1. Karl Palmskog Translated by: Siavash Soleimanifard. September 2011

Transcription

1 Programsystemkonstruktion med C++: Övning 1 Karl Palmskog palmskog@kth.se Translated by: Siavash Soleimanifard September 2011

2 Programuppbyggnad Klassens uppbyggnad A C++ class consists of a declaration and definition Declaration, usually in.h (.hh) and the definition in.cpp (.cc) private is the default for functions and variables in classes Global functions and variables is OK main is a global function Macro (starts with #) is driven by the preprocessor before compilation

3 Programuppbyggnad Example of declaration: inventory item.h #i f n d e f INVENTORY ITEM H #d e f i n e INVENTORY ITEM H #i n c l u d e <c s t d d e f > c l a s s I n v e n t o r y I t e m { p r i v a t e : double c o s t ; s i z e t u n i t s ; p u b l i c : s t a t i c const double DEF COST = 1 0 ; s t a t i c const s i z e t DEF UNITS = ; I n v e n t o r y I t e m ( ) : c o s t (DEF COST ), u n i t s ( DEF UNITS ) { I n v e n t o r y I t e m ( double c, s i z e t u ) ; I n v e n t o r y I t e m ( ) { double v a l u e ( ) const ; void removeunits ( s i z e t u ) ; ; #e n d i f

4 Programuppbyggnad Exampel of definition: inventory item.cpp #i n c l u d e i n v e n t o r y i t e m. h I n v e n t o r y I t e m : : I n v e n t o r y I t e m ( double c, s i z e t u ) { c o s t = c < 0? 0 : c ; u n i t s = u ; double I n v e n t o r y I t e m : : v a l u e ( ) const { r e t u r n c o s t u n i t s ; void I n v e n t o r y I t e m : : removeunits ( s i z e t u ) { i f ( u > u n i t s ) { u n i t s = 0 ; e l s e { u n i t s = u ;

5 Programuppbyggnad Exempel på användning av klassdeklaration: main.cpp #i n c l u d e i n v e n t o r y i t e m. h #i n c l u d e <i o s t r e a m > using namespace s t d ; i n t main ( ) { I n v e n t o r y I t e m d e f a u l t I t e m ; cout << d e f a u l t I t e m. v a l u e ( ) << e n d l ; I n v e n t o r y I t e m customitem ( 2 0, ) ; cout << customitem. v a l u e ( ) << e n d l ; customitem. removeunits ( 5 0 ) ; cout << customitem. v a l u e ( ) << e n d l ; customitem. removeunits ( ) ; cout << customitem. v a l u e ( ) << e n d l ; r e t u r n 0 ;

6 Kompilering och körning av program Examples of compilation and execution of programs Compilation with g++ directly to the program and run: $ g++ o i i main. cpp i n v e n t o r y i t e m. cpp $. / i i Equivalent to the object files compiled separately: $ g++ c i n v e n t o r y i t e m. cpp $ g++ c main. cpp $ g++ o i i main. o i n v e n t o r y i t e m. o With the warnings, debug symbols and optimization: $ g++ o i i d e b u g Wall g O1 main. cpp i n v e n t o r y i t e m. cpp

7 Kompilering och körning av program The program s path to the execution Källkod (.c,.cpp,.h,...) Bibliotekskod (.so,.a,.dll,...) Startkod Kompilator Objektkod (.o) Länkare Exekverbar kod (.exe,...)

8 Kompilering och körning av program Depending Handling If we change the main.cpp it suffices to recompile If we change the inventory item.cpp/h, we might compile on both inventory item.cpp and main.cpp Hard to keep track of dependencies Always recompile everything is slow interesting error about everything that needs to compile does not recompile A solution: use the tool make

9 Kompilering och körning av program A simple Makefile i i : main. o i n v e n t o r y i t e m. o g++ o i i main. o i n v e n t o r y i t e m. o main. o : main. cpp i n v e n t o r y i t e m. h g++ c main. cpp i n v e n t o r y i t e m. o : i n v e n t o r y i t e m. cpp i n v e n t o r y i t e m. h g++ c i n v e n t o r y i t e m. cpp c l e a n : rm f main. o i n v e n t o r y i t e m. o i i

10 Kompilering och körning av program A more advanced Makefile CC = g++ FLAGS = g I / l i b s OBJ = main. o i n v e n t o r y i t e m. o SRC = main. cpp i n v e n t o r y i t e m. cpp PROG = i i $ (PROG) : $ (OBJ) $ (CC) $ (FLAGS) o $ (PROG) $ (OBJ) %.o : %.cpp $ (CC) $ (FLAGS) c $. cpp c l e a n : rm f. o $ (PROG) depend : $ (SRC) makedepend $ ( FLAGS) $ˆ

11 Språkfunktionalitet Preprocessor Directives #include merge files before compiling #ifndef... #define... #endif ensures that a file included only once // may be u s e f u l #d e f i n e MAX // dangerous #d e f i n e SQR1(A) A A // l e s s dangerous #d e f i n e SQR2(A) (A) (A)

12 Språkfunktionalitet Function main function main is special can not be called anything else argc is the number of arguments incl. program name argv is an array of C-strings using the arguments given to program argv[0] is the program name (e.g., /usr/bin/zip or zip) main is a global function and not part of any class main no need to be declared

13 Språkfunktionalitet Pointers void f o o ( I n v e n t o r y I t e m i t ) { i n t ptr, i ; // p t r i s p t r to i n t, i i s i n t i n t x, y ; // x i s p t r to i n t, y i s i n t p t r = &i ; // p t r now h o l d s a d d r e s s o f i ( e. g. 0 x b f f f f f 2 4 ) p t r = 5 ; // a s s i g n 5 to i x = p t r ; // x now a l s o p o i n t s to i cout << x << e n d l ; // would p r i n t 5 ( i t ). removeunits ( 1 0 ) ; i t >removeunits ( 1 0 ) ; p t r = new i n t ; // p t r now h o l d s adr o f i n t on heap p t r = &y ;

14 Språkfunktionalitet Pointers void f o o ( I n v e n t o r y I t e m i t ) { i n t ptr, i ; // p t r i s p t r to i n t, i i s i n t i n t x, y ; // x i s p t r to i n t, y i s i n t p t r = &i ; // p t r now h o l d s a d d r e s s o f i ( e. g. 0 x b f f f f f 2 4 ) p t r = 5 ; // a s s i g n 5 to i x = p t r ; // x now a l s o p o i n t s to i cout << x << e n d l ; // would p r i n t 5 ( i t ). removeunits ( 1 0 ) ; i t >removeunits ( 1 0 ) ; p t r = new i n t ; // p t r now h o l d s adr o f i n t on heap p t r = &y ; // no way to a c c e s s memory anymore

15 Språkfunktionalitet Pointers and Arrays void f o o ( f l o a t f ) { char a r r a y [ ] ; // a r r a y o f 4711 u n i n i t i a l i z e d c h a r s i n t a r y [ ] = { 1, 2, 5 ; // a r r a y o f 3 i n i t i a l i z e d i n t s // same as c o n s t c h a r s t r [ ] = { h, e, j, 0 ; char s t r [ ] = h e j ; char p t r = 0 ; // c h a r p o i n t e r to n o t h i n g const f l o a t f P t r ; // memory p o i n t e d to i s r e a d o n l y f l o a t const f c P t r=f ; // p o i n t e r f i s r e a d o n l y p t r = a r r a y ; // same as p t r = &a r r a y [ 0 ] ; p t r [ 4 ] = x ; // s e t f i f t h element o f a r r a y to x ( p t r + 4) = y ; // same t h i n g, but to y p t r = new char [ ] ; // d y n a m i c a l l y a l l o c a t e d a r r a y

16 Språkfunktionalitet Referencing alias for an object as a pointer whose address can not be changed must refer to an object (not NULL) void iswap ( i n t &i1, i n t &i 2 ) { i n t tmp = i 1 ; i 1 = i 2 ; i 2 = tmp ; void main ( ) { i n t i = 5 ; i n t &i R e f = i ; i n t i P t r = &i ; i R e f ++; // i, i R e f and i P t r i s now 6

17 FAQs Common mistakes void f o o ( i n t p ) { d e l e t e p ; i n t bar ( ) { i n t x = 1 ; r e t u r n &x ; void fun ( ) { i n t p1, p2 ; i n t p3 = new i n t [ 2 ] ; i n t p4 = new i n t [ 2 ] ; p3 = p4 ; f o o ( p3 ) ; i n t x = p4 [ 1 ] ;

18 FAQs Common mistakes void f o o ( i n t p ) { d e l e t e p ; i n t bar ( ) { i n t x = 1 ; r e t u r n &x ; // oops! void fun ( ) { i n t p1, p2 ; // p2 i s normal i n t not p o i n t e r i n t p3 = new i n t [ 2 ] ; i n t p4 = new i n t [ 2 ] ; p3 = p4 ; // MEMORY LEAK! f o o ( p3 ) ; // d e s t r u c t i o n o f p3 ( and p4 ) i n t x = p4 [ 1 ] ; // e r r o r ( s e g f a u l t i f LUCKY)

19 FAQs Common errors at compile calls to functions whose header was not included with the include, to use the cout must be such as to have #include<iostream> calls to functions in the namespace std without having declared using namespace std, call to cout must then be written std:: court all object files are not compiled on the code updating use of C-compiler gcc instead of g++ functions used are not declared as public (private is the default) class declaration does not end with a semicolon

20 Testning Testing testing is the process of testing some of the executions of a system for a given criteria. unit testing is the process to test the smallest components of a system (functions and classes) in an isolated environment. Some reasons for testing: evidence that the code does what it should allows restructuring with the same functionality faster localization of introduced bugs Test early. Test often. Test automatic.

21 Testning Testramverket cxxtest test framework for C++ which only requires a compiler and Python tests are written in a separate file, executable code generated by scripting test is organized into test suites (test suites) in the test functions are claims with macros such as TS ASSERT and TS ASSERT EQUALS for more information on the cxxtest

22 Testning Exampel on unit testing: inventory item test.cpp #i n c l u d e <c x x t e s t / T e s t S u i t e. h> #i n c l u d e i n v e n t o r y i t e m. h c l a s s I n v e n t o r y I t e m T e s t : p u b l i c CxxTest : : T e s t S u i t e { p u b l i c : void t e s t d e f a u l t c o s t a n d u n i t s ( void ) { I n v e n t o r y I t e m i t ; TS ASSERT EQUALS( i t. v a l u e ( ), I n v e n t o r y I t e m : : DEF COST I n v e n t o r y I t e m : : DEF UNITS ) ; void t e s t n e g a t i v e c o s t ( void ) { I n v e n t o r y I t e m i t ( 10, ) ; TS ASSERT EQUALS( i t. v a l u e ( ), 0 ) ; ;

23 Testning Makefile for cxxtest CC = g++ FLAGS = g OBJ = i n v e n t o r y i t e m. o PROG = t e s t r u n n e r t e s t r u n n e r. o $ (PROG) : $ (OBJ) $ (CC) $ (FLAGS) o $ (PROG) $ (OBJ) %.o : %.cpp $ (CC) $ (FLAGS) c $. cpp t e s t r u n n e r. cpp : i n v e n t o r y i t e m t e s t. cpp i n v e n t o r y i t e m. h c x x t e s t g e n. py e r r o r p r i n t e r o t e s t r u n n e r. cpp \ i n v e n t o r y i t e m t e s t. cpp c l e a n : rm f. o $ (PROG) t e s t r u n n e r. cpp

24 Testning Running tests $ make g++ g c i n v e n t o r y i t e m. cpp c x x t e s t g e n. py e r r o r p r i n t e r o t e s t r u n n e r. cpp \ i n v e n t o r y i t e m t e s t. cpp g++ g c t e s t r u n n e r. cpp g++ g o t e s t r u n n e r i n v e n t o r y i t e m. o t e s t r u n n e r. o $. / t e s t r u n n e r Running 2 t e s t s.. OK! If cost can find negative values: $. / t e s t r u n n e r Running 2 t e s t s. I n I n v e n t o r y I t e m T e s t : : t e s t n e g a t i v e c o s t : i n v e n t o r y i t e m t e s t. cpp : 1 5 : E r r o r : Expected ( i t. v a l u e ( ) == 0 ), found ( != 0) F a i l e d 1 o f 2 t e s t s S u c c e s s r a t e : 50%