The C++ Compiler

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% CC -readme

Figure 1-1 Organization of the C++ Compilation System.

Table 1-1 summarizes the components of the C++ compilation system.

Table 1-1 Components of the C++ Compilation System 

Component	Description	Notes on Use
ccfe	Front end (Compiler preprocessor and compiler)
iropt	Code Optimizer	(SPARC) -O, -xO[2-5], -fast
cg386	Intermediate language translator	(x86) Always invoked
cgppc	Intermediate language translator	(PowerPC) Always invoked
inline	Inline expansion of assembly language templates	.il file specified
mwinline	Automatic inline expansion of functions	(x86) (PowerPC) -xO4, -xinline
fbe	Assembler
cg	Code generator, inliner, assembler	(SPARC)
codegen	Code generator	(x86) (PowerPC)
tdb_link	Template pre-linker
ld	Non-incremental editor
ild	Incremental link editor	-g, -xildon

The C++ compiler package also includes:

• On-line README files containing the latest known software and documentation bugs and other late-breaking information

• Man pages--single-page (generally), online documentation that concisely describes a user command or library function

• The C++ name demangling tool set (dem and c++filt)

• C++ library functions for stream I/O, complex arithmetic, tasking, and other operations

• Tools.h++ class library--a set of C++ classes that can simplify your programming

• #include files--files you can use for standard features such as signals and ctype with C++ programs

• lex--Generates programs used in simple lexical analysis of text
• yacc--Generates a C function to parse input stream according to syntax
• prof--Produces an execution profile of modules in a program
• gprof--Profiles by procedure

C++ is designed as a superset of the C programming language. While retaining the efficient low-level programming, C++ adds:

• Stronger type checking
• Extensive data abstraction features
• Support for object-oriented programming

Type Checking

Rather than having the C++ compiler do these automatic conversions, you can explicitly convert between types, just as you can in C.

A related area involves overloaded function names. In C++, you can give any number of functions the same name. The compiler decides which function should be called by checking the types of the parameters to the function call. This action may lead to ambiguous situations. If the resolution is not clear at compile time, the compiler issues an "ambiguity" error.

Classes and Data Abstraction

carrot1 + carrot2

has a value determined by your definition of + in the case of carrots. This definition does not override the original definition of +; as with overloaded function names, the compiler determines from context what definition of + it should use. Operators with extra definitions like this are called overloaded operators.

In addition to operators, classes may have member functions, functions that exist to operate on objects of that class.

C++ provides classes as a means for data abstraction. You decide what types (classes) you want for your program's data and then decide what operations each type needs.

The members of a class can be divided into three parts: public, private, and protected. The public part is available to any function; the private part is available only to member and friend functions; the protected part is available to members, friends, and members of derived classes.

Object-Oriented Features

Native Language Support

In general, the C++ compiler implements internationalization as follows:

• C++ recognizes ASCII characters from international keyboards (in other words, it has keyboard independence and is 8-bit clean).

• C++ allows the printing of some messages in the native language.

• C++ allows native language characters in comments, strings, and data.

You can change your application from one native language to another by setting the locale. For information on this and other native language support features, see the operating system documentation.

Compatibility With C

C++ does have some important differences from C; an ordinary C program may not be accepted by the C++ compiler without some modifications. Chapter 7, "Moving From C to C++," discusses what you must know to move from programming in C to programming in C++.

Even though the differences between C and C++ are most evident in the way you can design interfaces between program modules, C++ retains all of C's facilities for designing such interfaces. You can, for example, link C++ modules to C modules, so you can use C libraries with C++ programs.

C++ differs from C in a number of other details. In C++:

• Defined constants allow you to avoid the preprocessor and use named constants in your program.

• Function prototypes are required.

• Free store operators new and delete create dynamic variables.

• References, alternate "handles" on the same object, are automatically dereferenced pointers and act like an alternate name for a variable. You can use references as function parameters.

• Functional syntax for type coercions is supported.

• Programmer-defined automatic type conversion is allowed.

• Variable declarations are allowed anywhere, not just at the beginning of the block.

• A new comment delimiter begins a comment that continues to the end of the line.

• The name of an enumeration or class is also automatically a type name.

• Default values can be assigned to function parameters.

• Inline functions can ask the compiler to replace a function call with the function body, improving program efficiency.