The University of Iowa The College of Liberal Arts and Sciences Department of Computer Science
Lecture/Lab #26
Preprocessor, separate compilation
source-1.cpp
source-2.cpp
Object file 1
Object file 2
Executable
Compilation
Linking
Preprocessor
Compiler
The preprocessor is executed after tokenization and before compilation.
The result of preprocessing is a single file which is then passed to the actual compiler.
https://repl.it/@agurtovoy/lab26-preprocessor
https://repl.it/@agurtovoy/lab26-preprocessor-directives
Every preprocessor directive starts with the # character
#include <header>
#include "header"
Includes header file into current source file at the line immediately after the directive.
#define IDENTIFIER
#define IDENTIFIER replacement
#define IDENTIFIER( args ) replacement
Defines IDENTIFIER as macro, instructing the compiler to replace all successive occurrences of IDENTIFIER with its replacement (if any).
#undef IDENTIFIER
Cancels previous definition of IDENTIFIER by #define directive (if any).
#if expression / #ifdef IDENTIFIER / #ifndef IDENTIFIER
#else / #elif expression
#endif
Conditional compilation of parts of the source file.
#error error message
Shows the error message and renders the program ill-formed.
https://repl.it/@agurtovoy/lab26-separate-compilation
point.cpp
point.hpp
point interface
point implementation
#include <point.hpp>
organism.cpp
use point
Ability to organize a program into a set of independent physical "modules"
Headers can include other headers.
Headers allows us to ensure that the entity declarations are the same in each file.
Because a header might be included more than once, we need to write headers in a way that is safe even if the header is included multiple times.
A .cpp file with all the header files included is called a translation unit.
Standard way: #include guards
East way: #pragma once
Marking a function definition as inline allows us to keep its in a header.
By Aleksey Gurtovoy
