[PATCH] Report dlsym, dlvsym lookup errors using dlerror [BZ #19509]

[Florian Weimer]

* Martin Sebor:

> So AFAICS, the patch does the right thing.  I would only suggest to
> enhance the test to verify that dlerror() does return a null pointer
> when no error has occurred (e.g., the second call to dlerror() with
> no other intervening dlxxx() calls should return null).

Fair enough, I will put this into the test.

Have you and Carlos looked at more than the test? :)

I'm worried that I'm missing something in the callgraph—as far as I
can tell, the change only affects RTLD_NEXT, but it seems bizarre that
there wasn't any error reporting specifically for that.