On Mon, Oct 8, 2012 at 9:37 PM, Sagar Behere <sagar [dot] behere [..] ...> wrote:
> Hello,
>
> I have a struct like
>
> typedef struct __attribute__ ((__packed__))
> {
> uint8_t x;
> int16_t y;
> uint32_t z;
> double p;
> } MyDataType;
>
> This doesn't work with typegen, unless the __attribute__ ((__packed__))
> is removed. The error is
>
> --------
> [ 15%] Building CXX object
> CMakeFiles/foo-typekit-gnulinux.dir/type_info/MyDataType___std__string.cpp.o
> In file included from
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/type_info/MyDataType___std__string.cpp:4:0:
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/types/foo/type_info/BoostSerialization.hpp:
> In instantiation of ‘void boost::serialization::serialize(Archive&,
> MyDataType&, unsigned int) [with Archive = RTT::types::type_discovery]’:
> /usr/include/boost/serialization/serialization.hpp:128:9: required
> from ‘void boost::serialization::serialize_adl(Archive&, T&, unsigned
> int) [with Archive = RTT::types::type_discovery; T = MyDataType]’
> /usr/include/boost/archive/detail/iserializer.hpp:373:13: required
> from ‘static void
> boost::archive::detail::load_non_pointer_type<Archive>::load_only::invoke(Archive&,
> const T&) [with T = MyDataType; Archive = RTT::types::type_discovery]’
> /home/sagar/excludes/orocos-toolchain/install/include/rtt/types/type_discovery.hpp:164:17:
> required from ‘void RTT::types::type_discovery::discover(T&) [with T
> = MyDataType]’
> /home/sagar/excludes/orocos-toolchain/install/include/rtt/types/StructTypeInfo.hpp:87:17:
> required from ‘std::vector<std::basic_string > RTT::types::StructTypeInfo<T, has_ostream>::getMemberNames() const [with
> T = MyDataType; bool has_ostream = false]’
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/type_info/MyDataType___std__string.cpp:90:67:
> required from here
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/types/foo/type_info/BoostSerialization.hpp:30:1:
> error: cannot bind packed field ‘b.MyDataType::y’ to ‘short int&’
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/types/foo/type_info/BoostSerialization.hpp:31:1:
> error: cannot bind packed field ‘b.MyDataType::z’ to ‘unsigned int&’
> /home/sagar/excludes/orocos-playground/src/datatypes/src/types/types/foo/type_info/BoostSerialization.hpp:32:1:
> error: cannot bind packed field ‘b.MyDataType::p’ to ‘double&’
> make[2]: ***
> [CMakeFiles/foo-typekit-gnulinux.dir/type_info/MyDataType___std__string.cpp.o]
> Error 1
> make[1]: *** [CMakeFiles/foo-typekit-gnulinux.dir/all] Error 2
> make: *** [all] Error 2
> ---------
>
> Is there a way to get typegen working with __attribute__ ((__packed__)) ?

Sylvain is right, it's not typegen. We generate some boost functions
that take a reference to the
fields of your struct. Since taking a reference to a packed member
variable might fail at runtime
on some systems, the compiler bails out.
I've seen reports of other compiler versions accepting it though...
which is weird.

I've seen workarounds that use pointers instead of references, which
would mean that we have to
make a major api change in the typekit/boost functions.

This is the patch for gcc that introduced this error:
http://gcc.gnu.org/ml/gcc-patches/2003-07/msg01664.html

I didn't see that coming when I created that API. Maybe we can
encapsulate the change such that only
typegen generated code sees it, which would be fine since typegen
typekits are always generated (so no
legacy code to update).

Peter

Hi Sagar,

On Mon, Oct 8, 2012 at 9:37 PM, Sagar Behere <sagar [dot] behere [..] ...> wrote:
> Hello,
>
> I have a struct like
>
> typedef struct __attribute__ ((__packed__))
> {
> uint8_t x;
> int16_t y;
> uint32_t z;
> double p;
> } MyDataType;
>
> This doesn't work with typegen, unless the __attribute__ ((__packed__))
> is removed. The error is

mmm. I vaguely remember 'all is supported except packed and virtuals'.
Sylvain will clarify.

I really like it how you keep rubbing the edges of all this :-)

Now we really need to come to a point where this all works for you.

Peter

PS: Nice blog ! Feels like kst with pictures :-)