PIPE_DATA_BLOCK_SIZE   47 maint/gnulib/tests/test-nonblocking-pipe-child.c   main_reader_loop (test, PIPE_DATA_BLOCK_SIZE, STDIN_FILENO);
PIPE_DATA_BLOCK_SIZE  104 maint/gnulib/tests/test-nonblocking-pipe-main.c     main_writer_loop (test, PIPE_DATA_BLOCK_SIZE, STDOUT_FILENO, false);