olaf@pc:/tmp$ cat test.c
void or() {}

int main() {
        or();
}
olaf@pc:/tmp$ gcc test.c
olaf@pc:/tmp$ cat test.cpp 
void or() {}

int main() {
        or();
}
olaf@pc:/tmp$ g++ test.cpp 
test.cpp:1: Fehler: expected unqualified-id before »||« token
test.cpp: In function »int main()«:
test.cpp:4: Fehler: expected primary-expression before »||« token
test.cpp:4: Fehler: expected primary-expression before »)« token