Like was done for AP_HAL_Linux in 2ac96b9 ("AP_HAL_Linux: remove prefix
from AP_HAL_Linux classes"), remove the "Empty" prefix from class names
since we are already inside the Empty namespace.
These are "left-overs" from how things worked before commit
"AP_HAL: make code not depend on concrete HAL
implementations". The real declaration now lives inside get_HAL() function.
Use the opportunitiy to change the files to use "#pragma once".
prog_char and prog_char_t are now the same as char on supported
platforms. So, just change all places that use them and prefer char
instead.
AVR-specific places were not changed.
Move the macros to a single place and reduce the variations not based on
board, but based on
- The name of the entry-point function, specified by AP_MAIN;
- Whether it contains argc/argv arguments or not.
The goal here is that programs (vehicles and examples) don't need to
include all possible boards to define a main function. Further patches
will change the programs.
Instead of requiring every program to specify the HAL related modules,
let the build system do it (in practice everything we compiled depended
on HAL anyway). This allow including only the necessary files in the
compilation.
The switching between different AP_HAL was happening by giving different
definitions of AP_HAL_BOARD_DRIVER, and the programs would use it to
instantiate.
A program or library code would have to explicitly include (and depend)
on the concrete implementation of the HAL, even when using it only via
interface.
The proposed change move this dependency to be link time. There is a
AP_HAL::get_HAL() function that is used by the client code. Each
implementation of HAL provides its own definition of this function,
returning the appropriate concrete instance.
Since this replaces the job of AP_HAL_BOARD_DRIVER, the definition was
removed.
The static variables for PX4 and VRBRAIN were named differently to avoid
shadowing the extern symbol 'hal'.
This commit changes the way libraries headers are included in source files:
- If the header is in the same directory the source belongs to, so the
notation '#include ""' is used with the path relative to the directory
containing the source.
- If the header is outside the directory containing the source, then we use
the notation '#include <>' with the path relative to libraries folder.
Some of the advantages of such approach:
- Only one search path for libraries headers.
- OSs like Windows may have a better lookup time.
