Fix warning that reveals a real bug:
In file included from libraries/AP_HAL_Linux/UARTDriver.cpp:25:0:
libraries/AP_HAL_Linux/UARTDriver.cpp: In member function 'virtual bool Linux::UARTDriver::tx_pending()':
libraries/AP_HAL/utility/RingBuffer.h:21:35: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
#define BUF_EMPTY(buf) buf##_head == buf##_tail
^
libraries/AP_HAL_Linux/UARTDriver.cpp:355:13: note: in expansion of macro 'BUF_EMPTY'
return !BUF_EMPTY(_writebuf);
The problem is when there's a ! operator: without the parenthesis we would actually be doing
return !_write_buf_head == _write_buf_tail
which is not what we want.
Andrew Tridgell
Lucas De Marchi