Created attachment 29219 [details]
the bug code

system version :64-bit Ubuntu 12.04 lts
gcc version: 4.6.3
options:gcc source.c -o source
When compile and run a program with an error which will cause buffer overflow,the compiler can not dectect it.
The program below can compile and run correctly in my system(also works on my friend system which is no ubuntu but with gcc version 4.5.0)
#include <stdio.h>
#include <string.h>
main()
{
	const char *a="123456789abcdef";
	char b[10];
	int i=0;
	while((b[i]=a[i])!='\0')
	  ++i;
	printf("%s,%d\n",b,strlen(b));
	return 0;
}
I attempt to copy a string whose length is 15 to a array whose length is 10,and it compiles and run correctly.The output is "123456789abcdef,15".
p.s. This will not succeed in 32-bit linux system.