Yarp: Aborted core opening ports starting with "="

[Nicogene]

For unknown reasons it is supported =as starting character for port names, in alternative to / but it crashes 😄 e.g.:

yarp read =ciao
terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::substr: __pos (which is 18446744073709551615) > this->size() (which is 4)
Aborted (core dumped)

The magic number 18446744073709551615 should be std::string::npos.

Two possible fixes:

• We drop the = as starting character( there will be someone that used to open ports with =). 👍
• We fix this bug. ❤️

Vote what you prefer!

Yet Another Mysterious Behaviour Supported.

[drdanz]

I'd say we drop the '=' starting character, but we should definitely investigate whether there is some reason why this was added.

[Nicogene]

@damn1 and I discovered that adding in NestedContact.cpp

        if (idx == ConstString::npos) return false;

for avoing this out of range, typing yarp read =ciao you will have:

$ yarp read =ciao
yarp: Port /tmp/port/1 active at tcp://10.255.111.75:10002/
yarp: Port /tmp/port/2 active at tcp://10.255.111.75:10004/
yarp: Port /tmp/port/2=ciao active at tcp://10.255.111.75:10003/

So we tried, in Port.cpp, to remove = among the allowed starting character and we had:

$ yarp read =ciao
yarp: Port /tmp/port/1 active at tcp://10.255.111.75:10002/
yarp: Port name '=ciao/tmp/port/1' needs to start with a '/' character

without closing the yarp read...

On the other hand we found a "working" usage of =

$ yarp read /ciao=/ciaone
yarp: Port /ciao active at tcp://10.255.111.75:10005/
yarp: Port /ciaone-@/ciao active at tcp://10.255.111.75:10004/

[damn1]

  | @ |   | =
-- | ---- | -- | ------
/p1@/p2 | - node /p2 is opened
- open port /p1[cat]@/p2
- subscribe to topic /p1 | /p2=/p1 | same result
/p1@p2 | - :exclamation: no leading "/" for p2
- open port /p1[cat]@p2
- subscribe to topic /p1 | p2=/p1 | p2=/p1 has to start with “/”, do nothing
p1@/p2 | no leading “/”, do nothing | /p2=p1 | :exclamation: DUMP
/p1@ | - node /tmp/port/(n)
- open /p1[cat]@/tmp/port/(n)
- subscribe to topic /p1 | =/p1 | - node /tmp/port/(n)
- :exclamation: open /p1/tmp/port/n[cat]@
- :exclamation: subscribe to topic /p1/tmp/port/(n)
(with a ‘node name mismatch’ fail)
p1@ | no leading “/”, do nothing | =p1 | :exclamation: DUMP
p1/p2@ | no leading “/”, do nothing | =p1/p2 | - :exclamation: p1 is taken as the category
- node tmp/port/(n) opened
- :exclamation: also node tmp/port/(n+1) is opened
- :exclamation: also /tmp/port/(n+1)=p1/p2 is opened.
No topic subscription.
@/p1 | no leading “/”, do nothing | /p1= | :exclamation: DUMP
@ | no leading “/”, do nothing | = | :exclamation: DUMP
/p1@/ |- :exclamation: node / is opened
- open /p1[cat]@/
- subscribe to /p1 | /=/p1 | same result

This table shows the result of the use of the two syntaxes. I added an :exclamation: where I think the behaviour is broken. So if its ok, I would drop the = checks as @drdanz commented. And I would add a regex control function as first thing to be called on the input string in Port::open(), to avoid problems I found in the @ syntax, like registering a port named just /.

[damn1]

Some other information:

1. also /node#/port syntax is supported as alternative to '@' syntax.
2. registering ports named ...string is allowed, but then they are not connectable since #1441
3. yarp read "" results in yarp: Anonymous port active at tcp://10.255.111.155:37571/ (port number is quite random) but this port is not registered and is not visible in the name server.

Since I'm already writing a patch I would drop 2. and 3. as I think they're not expected behaviours.

[damn1]

Another buggy behaviour:

yarp read /n1=-/p
yarp: Port /n1 active at tcp://10.255.111.155:10006/
yarp: Port /n1=-/p active at tcp://10.255.111.155:10005/

yarp read /n=/p
yarp: Port /n active at tcp://10.255.111.155:10003/
yarp: Port /p-@/n active at tcp://10.255.111.155:10002/

If you explicit category, yarp leave the port name as it is. If you don't specifify it yarp chooses one and changes the name syntax from '=' to '@' .
I think the behaviour should be unified, change always or change never. Same happens with '#'.
Moreover, if you specify category, there is no check on currentCore->commitToRead or currentCore->commitToWrite so one can open a port with + category with read command...

Also I see from NodeTest before testing names, this:
report(0,"check support for various experimental node/topic/service schemes");
So if these syntaxes are 'experimental' we could unify them to '@' only.