[boost] Boost::any typecasting issue(bad_any_cast)

[Daggumati, Rajesh via Boost]

Hi Team,

While doing typecasting from boost::any to DecodeErrorPayload_t, its throwing bad_any_cast ..

class RegisterIONotification
{
public:
enum NotifyType {
TypeUnknown,
TypeRegTx,
TypeRegRx,
TypeDecodeError
};
NotifyType Type;
boost::any Payload;
typedef boost::tuple<std::string, BinaryBuffer_t> DecodeErrorPayload_t;
RegisterIONotification(NotifyType type;,boost::any payload)
{
Type(type);
Payload(payload);
}
};

I have called RegisterIONotification from other class function.

void RegisterIOThreaded::OnDecodeError( const std::string& error, BinaryBuffer_t data )
{
RegisterIONotification notify(RegisterIONotification::TypeDecodeError ,make_tuple(error, data));
.....
....
...
}

While testing, I am getting bad_any_cast exception.

TEST_F(...,...)
{
RegisterIONotification notify = sink.GetDataById(ID::NOTIFY_COMMS_STATUS, 0).GetValue<RegisterIONotification>();
ASSERT_EQ(RegisterIONotification::TypeDecodeError, notify.Type); //passed
RegisterIONotification::DecodeErrorPayload_t payload;
ASSERT_NO_THROW(payload = boost::any_cast<RegisterIONotification::DecodeErrorPayload_t>(notify.Payload));// Here its got failed...Please help me to fix this.
}



Regards,
Rajesh D
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[Antony Polukhin via Boost]

On Sat, Dec 4, 2021, 00:48 Daggumati, Rajesh via Boost <
bo...@lists.boost.org> wrote:

> Hi Team,
>
> While doing typecasting from boost::any to DecodeErrorPayload_t, its
> throwing bad_any_cast ..
>

Please, provide a minimal example that *compiles, links* and reproduces the
problem.

Regards,
> Rajesh D
> Please be advised that this email may contain confidential information. If
> you are not the intended recipient, please notify us by email by replying
> to the sender and delete this message. The sender disclaims that the
> content of this email constitutes an offer to enter into, or the acceptance
> of, any agreement; provided that the foregoing does not invalidate the
> binding effect of any digital or other electronic reproduction of a manual
> signature that is included in any attachment.
>

You are sending emails to a public mailing list that is available for
anonymous reading from all over the world.

[Gavin Lambert via Boost]

On 19/11/2021 04:57, Daggumati, Rajesh wrote:
> typedef boost::tuple<std::string, BinaryBuffer_t> DecodeErrorPayload_t;
> RegisterIONotification(NotifyType type;,boost::any payload)

[...]

> void RegisterIOThreaded::OnDecodeError( const std::string& error, BinaryBuffer_t data )
> {
> RegisterIONotification notify(RegisterIONotification::TypeDecodeError ,make_tuple(error, data));

[...]

> ASSERT_NO_THROW(payload = boost::any_cast<RegisterIONotification::DecodeErrorPayload_t>(notify.Payload));// Here its got failed...Please help me to fix this.

You have to be *very* careful about using type inference and implicit
casts when using boost::any. For example, it's entirely possible that
make_tuple is returning a type that is compatible with
DecodeErrorPayload_t but is not actually DecodeErrorPayload_t, which
will cause your later any_cast to fail. (Especially if you're calling
std::make_tuple rather than boost::make_tuple, which seems likely.)

You can inspect the payload in a debugger to determine what type it
actually is (although it can be hard to interpret). Or, (while
undocumented) it does contain a type() method that you can call and log
to inspect the actual type.

You may get better results if you explicitly static_cast your make_tuple
call to the type that you're expecting, or use uniform construction
syntax instead of make_tuple.