Function mi_heap_dump_json 

pub unsafe extern "C" fn mi_heap_dump_json(
    include_blocks: bool,
    hash_addresses: bool,
) -> *mut c_char

Live per-heap -> per-page -> (optional) per-block JSON snapshot (issue #269, Bun parity P4). Backs Bun’s shipped bun:jsc heapStats({dump:true|"blocks"}). Returns NULL on allocation failure; a non-NULL result is mi_malloc-family memory the caller must free with mi_free (see prof::heap_dump_json for the safe wrapper).