What is a regression?

[Jason Merrill]

skaller wrote:
> But Jason, the compiler worked properly in rejecting invalid syntax.
> Now you're suggesting it fails to do so.  This suggests a real regression
> and a real bug: the new feature should have an enabling flag
> that couldn't have been set before it was implemented, and without
> that flag should create the same error in the current version.

The current version gives an error "ISO C++ does not include variadic 
templates" unless you enable C++0x mode.  And then crashes.

But in any case, nobody has code that relies on getting an error from a 
previous version of the compiler that would be broken by moving to 4.3. 
  Only regressions on valid code seem serious enough to me to warrant 
blocking a release.

> BTW: did WG21 already pass this proposal?

Yes, a few meetings back.

Jason