RTLD_LAZY vs RTLD_NOW in PluginLoader about gz-plugin

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

comment by @clalancette migrated from https://osrf-migration.github.io/ignition-gh-pages/#!/ignitionrobotics/ign-common/issues/34/rtld_lazy-vs-rtld_now-in-pluginloader (gazebosim/gz-common#34)#comment-44753481

My main concern with RTLD_LAZY vs. RTLD_NOW isn't really with performance, but more with debugging. As I see it, the big problem with RTLD_LAZY is that you don't find out if you can't resolve a symbol until you actually try to call that symbol. That means that the program may be successfully running for a while, and then when some new functionality gets invoked the program crashes because it can't resolve the symbol. If we did RTLD_NOW, then the symbol resolution would fail at program startup time and it is an easy thing for a developer to see, understand, debug, and fix.

With that said, I'd be in favor of just switching ignition to RTLD_NOW and leaving it at that. If we want to make it configurable, I'm fine with that too, but would prefer RTLD_NOW to be the default.

[osrf-migration]

Original comment by Michael Grey (Bitbucket: mxgrey, GitHub: mxgrey).

---

Failing early by default makes sense.

I would recommend a flag for the LoadLib(~) function, since I think whoever is loading the library would have the best sense of how it should be loaded. But being able to set the Loader's default in addition to that would be reasonable.