On Thu, May 29, 2014 at 5:13 AM, Pengyu Zhang <address@hidden> wrote:
I also think some configurations on my machine are not correct
Let's simplify the problem even more. It should be the case that when you place a xml file in /usr/local/share/gnuradio/blocks/ it will show up in GNU Radio Companion regardless of if you actually made the block. Do a sudo cp on howto_square2_ff.xml. Then open up GNU Radio and see if you can find the HOWTO category and the square block.