gcc _attribute_ under suse 64bit

[linux_starter]

Hey, I am new here, I have some problems with what indicated in the title, my test code as follows:
#include<iostream.h>

void sum(int,int)_attribute_((noreturn));
void sum(int a, int b)
{
int c = 0;
c = a + b;
printf("some sentence",c);
}

int main( void )
{
int a = 5;
int b = 10;
sum(a,b);
return 0;
}

but it seems the system cannot identify the key words _attribute_
in order to use it , what should I include or any change with my codes
-Note: it is just a test codes.

Thanks in advance

[Rubberman]

What are you trying to accomplish? This is not, AFAIK, a valid C-language construct. Just remove the line

void sum(int,int)_attribute_((noreturn));