GCC version: 3.2.3
Host: Linux

Sample code.

#include <netinet/in.h>

int main()
{
    unsigned short t;
    ::htons(t);
    return 0;
}

/usr/bin/g++  -O2 t.cpp     
t.cpp: In function `int main()':
t.cpp:10: syntax error before `__extension__'
t.cpp:10: `__x' undeclared (first use this function)
t.cpp:10: (Each undeclared identifier is reported only once for each function 
   it appears in.)
t.cpp:10: `__v' undeclared (first use this function)
t.cpp: At global scope:
t.cpp:10: syntax error before `)' token

If I don't use -O2 the code compiles. If I change ::htons to htons the code compiles even with -O2. Why does it fail for ::htons()