This program compiles:

#include <iostream>

int main()
{
    std::cout << _S << std::endl;
    
    return 0;
    
}

If started, it outputs : 8

output of my g++ -v:

Reading specs from /opt/csw/gcc4/lib/gcc/i386-pc-solaris2.8/4.0.2/specs
Target: i386-pc-solaris2.8
Configured with: ../sources/gcc-4.0.2/configure --prefix=/opt/csw/gcc4 --with-local-prefix=/opt/csw --with-gnu-as --with-as=/opt/csw/bin/gas --without-gnu-ld --with-ld=/usr/ccs/bin/ld --enable-threads=posix --enable-shared --enable-multilib --enable-nls --with-included-gettext --with-libiconv-prefix=/opt/csw --with-x --enable-java-awt=xlib --with-system-zlib --enable-languages=c,c++,f95,java,objc,ada
Thread model: posix
gcc version 4.0.2