Re: [Dbus-cxx-users] Method call which returns signed char (and takes time_t)?

[Rick L. V. Jr. <rvi...@cs...>]

Hello Patrick:

Patrick Allison wrote:
> Hi:
>
> I've just started using dbus-cxx, and I'm having a bit of difficulty. I'm
> trying to replicate the "callee_object"/"caller_object" example: in my
> case, the class method looks like
>
> char saw(time_t sec);
>
> That gave me errors compiling the "callee" portion:
>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h: In member function
> DBus::HandlerResult DBus::Method<T_return, T_arg1, sigc::nil, sigc::nil,
> sigc::nil, sigc::nil, sigc::nil,
> sigc::nil>::handle_call_message(std::shared_ptr<DBus::Connection>,
> std::shared_ptr<const DBus::CallMessage>) [with T_return = char, T_arg1 =
> long int]:
>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h:176: error: ambiguous
> overload for operator>> in i >> _val_1
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h:176: note: candidates
> are: operator>>(int32_t, long int) <built-in>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h:176: note:
> operator>>(uint32_t, long int) <built-in>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h:176: note:
> operator>>(uint64_t, long int) <built-in>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/method.h:176: note:
> operator>>(int64_t, long int) <built-in>
>
> I got around that problem by replacing "time_t" with an unsigned int, so
> that's not that big a deal, though I'd like to know if that can be fixed.
> I then hit a snag in the "caller" portion,
>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/message.h: In function
> DBus::MessageIterator DBus::operator>>(std::shared_ptr<const
> DBus::Message>, T&) [with T = signed char]:
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/methodproxy.h:109:   instantiated
> from T_return DBus::MethodProxy<T_return, T_arg1, sigc::nil, sigc::nil,
> sigc::nil, sigc::nil, sigc::nil, sigc::nil>::operator()(T_arg1) [with
> T_return = signed char, T_arg1 = unsigned int]
>
> /usr/local/include/dbus-cxx-0.1/dbus-cxx/message.h:182: error: no matching
> function for call to DBus::Message::operator>>(signed char&) const
>
> which then lists a bunch of operator>> with bool, uint8_t,
> int16_t,uint16_t,int32_t,uint32_t,int64_t,uint64_t,double, const char*,
> and std::string. It looks like int8_t is missing from that list.
>
> Anyway, I wasn't sure if this was a bug or something related to allowable
> DBus types, so I figured I'd ask. I can work around it by passing
> something larger than a char, obviously, but it seems strange for int8_t
> to be the only one that's missing.
>

Largely, it's related to the dbus types. DBus doesn't have a direct type
for char or int8_t but there is a BYTE type. I added support for both
since they are fundamental C types. I also added support for floats.

The problem with the long int was due to the fact that nothing in the DBus
types maps directly to it. On i386 int32_t maps to to int and int64_t maps
to long long skipping long.

I added support for long ints on 32-bit architectures only (since they're
already supported as int64_t on x86_64).

I also added an example that demonstrates how to overload the << and >>
operators for MessageIterator and MessageAppendIterator to support
additional types. In this example a timeval (with microsecond resolution)
is overloaded.

---

Rick