Question regarding extension detection

[Moreshwar Salpekar]

Hello,

This may have been asked earlier but I cant find it so I am asking again. If it is already asked, please let me know the link

I have two possible extensions A and B (for simplicity only). Both are derived from tlm_extension

I have a module name MOD (for simplicity again).  In this I am checking if extension A is attached or not.

I am not checking the extension B in MOD. It is just for tracking purposes. 

Extension A may or may not be present.

Therefore, i am making check like this

A *extA;

req->get_extension(ext); // tlm::tlm_generic_payload *req is the declaration

if (extA == nullptr) {

do ActionX

} else {

do ActionY

}

Now what is happening is

while sending a request to MOD, I attach extension B. There is not extension A attached. 

Therefore, I think that the check

if (extA == nullptr)

should return true. However, this is not the case. gdb is showing extA is actually B when doing p *extA.

I think this is because  both A and B are derived from tlm_extension.

Is there anyway, I can do a correct check so that if extension A is not present, it should extA as nullptr especially when A is not present but B is present.?

Regards

Moreshwar

[Moreshwar Salpekar]

I cant delete this post.

[Eyck]

The problem is that the pointer is not initialized. So :

A *extA{nullptr};
req->get_extension(ext); // tlm::tlm_generic_payload *req is the declaration
if (extA == nullptr) {
    do ActionX
} else {
    do ActionY
} 

should do the trick. BTW , a better soultion would be:

auto* extA = req->get_extension<A>();
if (extA == nullptr) {
    do ActionX
} else {
    do ActionY
} 

or even more concise:

if (auto* extA = req->get_extension<A>()) {
    do ActionY
} else {
    do ActionX
}