The Linux Development Platform Configuring, Using, and ... - Classes

CH03.fm Page 66 Monday, October 7, 2002 8:33 PM
66 Chapter 3 • Compilers and Assemblers
To create static binaries, you have to use –static command line option with gcc. To
created dynamically linked output binary files, use –shared on the command line.
For example, if we compile the hello.c program used earlier in this chapter with shared
libraries, size of the output executable file is 13644 bytes (this can be further reduced using the
strip utility discussed later in Chapter 7 of this book). However, if you compile it statically,
the size of the output binary file is 1625261 bytes, which is very large compared to the shared
binary. Note that this size can also be reduced using the strip utility.
To identify the dependencies of a dynamically linked binary file, you can use the ldd
command. The following command shows that linked output file hello depends upon two
dynamic libraries.
[rr@conformix 4]$ ldd hello
libc.so.6 => /lib/i686/libc.so.6 (0x4002c000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
[rr@conformix 4]$
If you copy hello to some other host, you also need to make sure that libc.so.6 and
ld-linux.so.2 exist on the target system.
On most of the Linux systems, dynamic linking is done by default.
3.3.7 Compiling Source Code for Other Languages
As mentioned earlier, the GCC set of compilers supports many languages. It can be used
to compile programs other than C language. Following is an introduction to compiling programs
from other languages.
3.3.7.1 Compiling C++ Code
C++ source code files have suffixes such as .C, .cpp, .cc, .c++, .cxx or .cp. The gcc compiler
recognizes these extensions and can compile C++ code. However you can also use g++ or
c++ compilers, which are part of the GCC compilers family and are installed with it. These programs
invoke gcc with appropriate options to compile C++ code and location of class files.
Using these programs, you can also compile C++ source code files that don’t have the standard
suffixes listed earlier.
3.3.7.2 Compiling Objective C Code
Objective files have suffixes such as .m and gcc recognizes Objective C files with that
suffix. When you compile Objective C code, you have to pass an option to the linker. This is
done using –lobjc. By this option, the linker uses Objective C libraries during the linking process.
Consider the following sample Objective C code (stored in hello.m file) to print “Hello
World” on the standard output.
#include "objc/Object.h"
@interface HelloWorld : Object
{