   gl.bindTransformFeedback(gl.TRANSFORM_FEEDBACK, null);
}

(async () => {
    debug("");
    debug("write-read");
    gl.copyBufferSubData(gl.COPY_READ_BUFFER, gl.COPY_WRITE_BUFFER, 0, 0, 8);
    checkGetBufferSubData(gl.NO_ERROR, "srcData");

    debug("");
    debug("fence-wait-write-read");
    await fence();
    gl.copyBufferSubData(gl.COPY_READ_BUFFER, gl.COPY_WRITE_BUFFER, 0, 0, 8);
    checkGetBufferSubData(gl.NO_ERROR, "srcData");

    debug("");
    debug("write-read-fence-wait");
    gl.copyBuff