#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_WIN8)

_Success_(return != 0)
NTSYSAPI
LOGICAL
NTAPI
RtlFreeHeap(
    _In_ PVOID HeapHandle,
    _In_opt_ ULONG Flags,
    _Frees_ptr_opt_ _Post_invalid_ PVOID BaseAddress
    );

#endif
#endif
View code on GitHub

#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_WIN8)
// ...
#else

_Success_(return)
NTSYSAPI
BOOLEAN
NTAPI
RtlFreeHeap(
    _In_ PVOID HeapHandle,
    _In_opt_ ULONG Flags,
    _Frees_ptr_opt_ PVOID BaseAddress
    );

#endif
#endif
View code on GitHub