This function accepts flags:

RB_NO_KEYWORDS, RB_PASS_KEYWORDS, RB_PASS_CALLED_KEYWORDS:
Works as the same as rb_block_call_kw.

RB_BLOCK_NO_USE_PACKED_ARGS:
The given block ("bl_proc") does not use "yielded_arg" of rb_block_call_func_t.
Instead, the block accesses the yielded arguments via "argc" and "argv".
This flag allows the called method to yield arguments without allocating an Array.