On Android operating systems, the getopt() function is posix compliant
and thus the option processing stops when the first non-option is found.
But the getopt_long() function permutes the argument vector, just like
the GNU implementation.
Using a leading '+' character in the option string disables the
permutation again.
The getopt function is defined in the unistd.h header file. This header
file is only available on posix compatible systems. For example, on
Windows it's not available when building without mingw.
String literals have the type 'char[N]' by default. Allthough they are
not really 'const', modifying a string literal is undefined behaviour.
Therefore, to avoid mistakes, libdivecomputer uses the -Wwrite-strings
compiler option to change the default type to 'const char[N]'.
The cast that triggers the -Wcast-qual warning can be avoided by using a
character array instead of string literal.
The device descriptor is either mandatory for a certain command (with
DCTOOL_CONFIG_DESCRIPTOR) or always NULL. But for some commands it will
be useful to support an optional descriptor as well. To support this, we
always try to lookup the device descriptor whenever the corresponding
command-line options are set.
When the device family is provided without an explicit model number, we
simply choose the first available model. But since new models are being
added all the time, this default model is not guaranteed to remain the
same. That's not desirable because it can alter the behaviour of the
application.
The introduction of the Aeris 500AI is an example of this problem. The
default model in the vtpro family used to be the Oceanic Versa Pro. But
because the Aeris 500AI has a lower model number, it automatically
became the new default model. Since both use a different protocol
variant (MOD vs INTR) they are not interchangable.
The default model is now hardcoded. The best option is of course to
provide the model number explicitly!
On BSD based operating systems (which includes Mac OS X), the getopt()
function is posix compliant and thus the option processing stops when
the first non-option is found. But the getopt_long() function permutes
the argument vector, just like the GNU implementation.
Using a leading '+' character in the option string disables the
permutation again.
The universal application works well, but is quite difficult to extend
with more functionality. Therefore a new and more modular application is
needed. The new dctool application will support multiple sub-commands,
to carry out specific actions. Extending the application will be as easy
as adding new commands.
