Function xmlMemSetup 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn xmlMemSetup(
    freeFunc: Option<xmlFreeFunc>,
    mallocFunc: Option<xmlMallocFunc>,
    reallocFunc: Option<xmlReallocFunc>,
    strdupFunc: Option<xmlStrdupFunc>,
)

Set custom memory allocator functions.

UPSTREAM-PARITY

void xmlMemSetup(xmlFreeFunc freeFunc,
                 xmlMallocFunc mallocFunc,
                 xmlReallocFunc reallocFunc,
                 xmlStrdupFunc strdupFunc);

SAFETY

• All function pointers must be valid (non-null) and thread-safe
• The functions must follow the C malloc/realloc/free/strdup contract
• Once set, the functions remain in effect until the next xmlMemSetup call
• The caller is responsible for ensuring the functions remain valid for the entire time they are installed