Fun with standards

This, as I understand it, is completely legitimate c99:

>$ cat main.c
#include <stdio.h>

inline void foo()
{
        printf("inline\n");
}

int main()
{
        foo();
        return 0;
}


>$ cat outline.c
#include <stdio.h>

void foo()
{
        printf("out-of-line\n");
}

>$ clang -O0 -c main.c -o main.o && clang -O0 -c outline.c -o outline.o && clang -o inline-test-O0 main.o outline.o
>$ clang -O2 -c main.c -o main.o && clang -O2 -c outline.c -o outline.o && clang -o inline-test-O2 main.o outline.o
>$ ./inline-test-O0
out-of-line
>$ ./inline-test-O2
inline