Function xmlMemUsed 

#[unsafe(no_mangle)]
pub extern "C" fn xmlMemUsed() -> c_int

Return the total amount of memory currently allocated (approximate).

UPSTREAM-PARITY

int xmlMemUsed(void);

Returns an approximate count of allocated bytes. With the default allocator, this tracks allocations but is not byte-exact for realloc (since we don’t track old sizes). Custom allocator hooks can provide exact counts.