order of defines not respected

[firewave]

void f()
{
#ifdef DEF_1
    int i;
#endif
}

$ ./simplecpp -DDEF_1 -UDEF_1 -DDEF_1 test.cpp
void f ( )
{



}

[firewave]

$ gcc -DDEF_1 -UDEF_1 -DDEF_1 -save-temps input.cpp | cat a-input.ii
# 0 "input.cpp"
# 0 "<built-in>"
# 0 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 0 "<command-line>" 2
# 1 "input.cpp"
void f()
{

    int i;

}