[cdt-dev] Support for C++14 constexpr evaluation

[Nathan Ridge <zeratul976@xxxxxxxxxxx>]

Hi folks,

Today I committed to the master branch a significant contribution by Toni Suter, a student at the Swiss university HSR. 

This contribution, tracked in bug 490475, adds support for C++14 constexpr evaluation, and introduces supporting infrastructure to instantiate function bodies and store them in the index.

In addition to advancing the state of our C++14 support, the supporting infrastructure to instantiate function bodies opens up many new possibilities for CDT features, such as Codan checking for and reporting errors that are instantiation-dependent, or "Find References" finding function calls that occur in a dependent context inside a template.

Toni, and before him another student Silvano Brugnoni, have been working on this for a long time, and after many rounds of review and testing we have finally merged it.

I'd like to extend a big thank you to Toni, to Silvano, and to their supervisor Peter Sommerlad, for this contribution!

As with any significant change, there is a risk of regressions. I have tested the change extensively on my own projects, but it's possible there are issues I didn't catch. My hope is that landing this early in the 9.2 cycle will give us plenty of time to work out any latent issues by the time the code becomes part of a release. If you do encounter regressions in parser or indexer functionality, please file bugs and cc me, and I will investigate them.

Regards,
Nate