Re: (OT?) Re: [musl] Symbol versioning approximation trips on compat symbols

[Rich Felker <dalias@libc.org>]

On Mon, Jan 28, 2019 at 04:22:45PM +0100, Markus Wichmann wrote:
> On Mon, Jan 28, 2019 at 02:08:13PM +0100, u-uy74@aetey.se wrote:
> > If there is a feature which is hard or impossible to test for, like
> > symbol versioning, it means that the applications may _have_ to rely on
> > an explicit build flag telling whether to use it.
> 
> Why is symbol versioning hard to test for, again? You make a library
> containing two versions of the same function, one returns one, the other
> two. The one that returns one is the default symbol. The test
> application tries to link against the version that returns two. If that
> works, symbol versioning is supported.

That's not a test for symbol versioning. At best that's a test for an
odd sort of bug under the assumption that symbol versioning is
basically supported.

If you're trying to identify the current situation with musl, what
you'd instead need to be testing for is failure to resolve a
*non-default* version at runtime when that's what should happen
according to the symbol versioning rules. The key here is that this is
a runtime test, making it invalid in the eyes of a large portion of
the community (myself included) who consider a test that can't work
when cross-compiling to be an invalid configure-time test.

Rich