libtest.a (was: Re: [PATCH] Fix p{readv,writev}{64} consolidation implementation)

[Florian Weimer <fweimer at redhat dot com>]

On 06/22/2016 01:05 PM, Mike Frysinger wrote:
> On 22 Jun 2016 11:57, Florian Weimer wrote:
> > On 06/15/2016 05:41 PM, Mike Frysinger wrote:
> > > > I think we should really have some sort of libtest.a, which provides
> > > > test helpers, error-checking functions such as xmalloc, and general
> > > > helpers for setting up special test environments.  I'm a bit worried
> > > > about figuring out the proper dependencies, so that libtest.a is built
> > > > before all the tests are linked.
> > >
> > > isn't this what test-skeleton.c does for us now ?  and we all agree that
> > > all tests should be using that.
> >
> > There are limits to what we can put into test-skeleton.c due to symbol
> > conflicts and dependencies of the test harness which are incompatible
> > with some things which we want to test.
>
> symbol-wise, i don't think there's a realistic problem.  we've rarely
> (ever?) run into this problem, and it's trivial to sort out by using
> a namespace prefix like "tst_".  which we probably want to do anyways
> to keep the API more readable.

What I mean is that the test harness pulls in stuff that cause things to 
interfere with what we want to test.  This could be magic symbols for 
stdio/libio compatibility, pthread symbols, or just calling mallopt (as 
discussed before).

If the test helpers are not in just one monolithic .c file, it helps 
with achieving that.

> dependency wise (e.g. dl or pthread usage), i'd wait until the need
> actually arises before i'd start worrying about it.

The need for pthread error-checking wrappers is already there.  Our 
current policy is to check error returns from *all* pthread functions, 
and getting a nice error from the usually looks like this:

  int ret = ...;
  if (ret != 0)
    {
      errno = ret;
      printf ("error: ...: %m\n");
      _exit (1);
    }

with some special exceptions such us pthread_barrier_wait.  Many tests 
are littered with that.

> > > imo we should just mandate all tests use the entry point "do_test" and it
> > > take argc/argv args (even if they're unused), and then all tests can pull
> > > test-skeleton.c in at the top.
> >
> > Yes, seems a reasonable improvement, and mostly unrelated.
>
> they are related when you look at the implications of the two paths.
> if we have a single test-skeleton.c, having a sep header for all the
> prototypes is kind of pointless and just busy work.  but if there's a
> lib of test files, then having a sep header is pretty much required.
> if there isn't a sep header, then the include point of the skeleton
> must be at the top since it's acting as the header.

In both cases, we want the include at the top, so the change your 
proposed goes in the right direction, whether we want a libtest.a or not.

Thanks,
Florian