Running Linux, 5th Edition - Matthias Kalle Dalheimer [379]
Several open source projects make it relatively easy to program in Java, and some of the tools and frameworks in the open source community are even more popular than those distributed by Sun Microsystems, the company that invented and licenses Java. Java is a general-purpose language with many potential Internet uses. In a later section, we explore what Java offers and how to get started.
Programming with gcc
The C programming language is by far the most often used in Unix software development. Perhaps this is because the Unix system was originally developed in C; it is the native tongue of Unix. Unix C compilers have traditionally defined the interface standards for other languages and tools, such as linkers, debuggers, and so on. Conventions set forth by the original C compilers have remained fairly consistent across the Unix programming board.
gcc is one of the most versatile and advanced compilers around. Unlike other C compilers (such as those shipped with the original AT&T or BSD distributions, or those available from various third-party vendors), gcc supports all the modern C standards currently in use—such as the ANSI C standard—as well as many extensions specific to gcc. Happily, however, gcc provides features to make it compatible with older C compilers and older styles of C programming. There is even a tool called protoize that can help you write function prototypes for old-style C programs.
gcc is also a C++ compiler. For those who prefer the more modern object-oriented environment, C++ is supported with all the bells and whistles—including most of the C++ introduced when the C++ standard was released, such as method templates. Complete C++ class libraries are provided as well, such as the Standard Template Library (STL).
For those with a taste for the particularly esoteric, gcc also supports Objective-C, an object-oriented C spinoff that never gained much popularity but may see a second spring due to its usage in Mac OS X. And there is gcj, which compiles Java code to machine code. But the fun doesn't stop there, as we'll see.
In this section, we cover the use of gcc to compile and link programs under Linux. We assume you are familiar with programming in C/C++, but we don't assume you're accustomed to the Unix programming environment. That's what we introduce here.
* * *
Warning
The latest gcc version at the time of this writing is Version 4.0. However, this is still quite new, sometimes a bit unstable, and, since it is a lot stricter about syntax than previous versions, will not compile some older code. Many developers therefore use either a version of the 3.3 series (with 3.3.5 being the current one at the time of this writing) or Version 3.4. We suggest sticking with either of those unless you know exactly what you are doing.
* * *
A word about terminology ahead: Because gcc can these days compile so much more than C (for example, C++, Java, and some other programming languages), it is considered to be the abbreviation for GNU Compiler Collection. But if you speak about just the C compiler, gcc is taken to mean GNU C Compiler.
Quick Overview
Before imparting all the gritty details of gcc, we present a simple example and walk through the steps of compiling a C program on a Unix system.
Let's say you have the following bit of code, an encore of the much overused "Hello, World!" program (not that it bears repeating):
#include int main() { (void)printf("Hello, World!\n"); return 0; /* Just to be nice */ } Several steps are required to compile this program into a living, breathing executable. You can accomplish most of these steps through a single gcc command, but we've left the specifics for later in the chapter.