erlang判断模块导出函数问题

1> erlang:function_exported(crypto,start,0).
false
2> crypto:start().
ok
3> erlang:function_exported(crypto,start,0).
true

-module(test).
-compile(export_all).

function_exported(Module, Function, Arity) ->
	case erlang:module_loaded(Module) of
		true ->
			next;
		_ ->
			code:load_file(Module)
	end,
	erlang:function_exported(Module, Function, Arity).

BIF_RETTYPE function_exported_3(BIF_ALIST_3)
{
    if (is_not_atom(BIF_ARG_1) || is_not_atom(BIF_ARG_2) ||  is_not_small(BIF_ARG_3)) {
        BIF_ERROR(BIF_P, BADARG);
    }
    if (erts_find_function(BIF_ARG_1, BIF_ARG_2, signed_val(BIF_ARG_3), 
            erts_active_code_ix()) == NULL) {
        BIF_RET(am_false);
    }
    BIF_RET(am_true);
}

/*
 * Find the export entry for a loaded function.
 * Returns a NULL pointer if the given function is not loaded, or
 * a pointer to the export entry.
 *
 * Note: This function never returns export entries for BIFs
 * or functions which are not yet loaded.  This makes it suitable
 * for use by the erlang:function_exported/3 BIF or whenever you
 * cannot depend on the error_handler.
 */

Export* erts_find_function(Eterm m, Eterm f, unsigned int a, ErtsCodeIndex code_ix)
{
    struct export_templ templ;
    struct export_entry* ee;

    ee = hash_get(&export_tables[code_ix].htable, init_template(&templ, m, f, a));
    if (ee == NULL ||	(ee->ep->addressv[code_ix] == ee->ep->code+3 &&
	 ee->ep->code[3] != (BeamInstr) BeamOp(op_i_generic_breakpoint))) {
        return NULL;
    }
    return ee->ep;
}

static IndexTable export_tables[ERTS_NUM_CODE_IX];  /* Active not locked */