about arrays initialization

[uulinux]

Dear all:

At first, read my code following please.
===============================================
	#include   <stdio.h>
	int main()
	{
		int a[5]={1, 2, 3, a[2], a[0]+a[1]};
		int i=0;

		for (i=0; i<5; i++) {
			printf("\t%d", a[i]);
		}
		return 0;
	}
===============================================

   There are not any error or warning log shown during compiling. The
result is as following:
===============================================
localhost array # gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-4.4.5/work/gcc-4.4.5/configure
--prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.4.5
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.4.5/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.4.5
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.4.5/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.4.5/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.4.5/include/g++-v4
--host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-ppl --without-cloog --enable-nls
--without-included-gettext --with-system-zlib --disable-werror
--enable-secureplt --disable-multilib --enable-libmudflap
--disable-libssp --enable-libgomp
--with-python-dir=/share/gcc-data/i686-pc-linux-gnu/4.4.5/python
--enable-checking=release --disable-libgcj --with-arch=i686
--enable-languages=c,c++,fortran --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.4.5
p1.2, pie-0.4.5'
Thread model: posix
gcc version 4.4.5 (Gentoo 4.4.5 p1.2, pie-0.4.5)

localhost array # gcc -o main main.c
localhost array # ./main
	1	2	3	-1218524971	-944870872
===============================================

   I want to know, what is wrong with it?