ABI breakages in 4.4

[Thomas Koenig]

On Sat, 2008-09-13 at 18:21 +0200, Richard Guenther wrote:

> c) Change passing the enlarged struct in such a way that it can
> be distinguished from old ones, such as passing an invalid known
> value in one of the old fields, duplicating it in the new parts.

This sounds doable, there should still be free bits in
st_parameter_common.flags ...

This kind of problem is easy to generate, and in the absence of testing,
hard to spot. Is there an (easy) way to run the testsuite with an
earlier version of gcc to compile the programs, with a newly compiled
library library to pick up this sort of regression?