[C++] Fix dangling reference bug in getRandomName

[oversearch]

Motivation

The current getRandomName function contains a simple dangling reference bug: when it attempts to return a const char* string value from the temporary string returned by the std::stringstream::str function. This sometimes "works" anyway in release mode depending on the platform it's running on, but in debug mode on all the versions of GCC and CLANG I've tried it segfaults. This makes debugging the c++ client very annoying.

Modifications

I found the existing method for generating random strings rather obscure, so I both fixed the bug and simplified the code. I made use of boost::random to provide a much more straightforward implementation. I use this pattern often for random names in my company's production projects, and it works well.

Verifying this change

• Make sure that the change passes the CI checks.

This code is called every time the client subscribes to a topic, so it gets plenty of coverage throughout the tests. I also manually verified that it's working correctly by printing the random names while I was testing. I've already included this fix in a local build of Pulsar I'm using for a new product at FactSet, and it's working well there.

The CI checks are failing with some error about a website deployment that seems unrelated to the C++ client. Is this a problem? Please let me know if I need to do anything special to get those checks to pass. Thanks!

[BewareMyPower]

The CI uses clang-format 5.0 to check code style so you should reformat your code before pushing a commit. And C++11 already has std::random, I think using C++ standard library is preferred to Boost if they have the same API.

[oversearch]

Thank you for the feedback! I forgot about the STL getting boost::random. I've switched the implementation and applied clang-format (for some reason CMake has trouble finding the clang-format binary on my machine...).

Hopefully all the required checks will succeed this time.

[BewareMyPower]

/pulsarbot run-failure-checks