[LLVMdev] C as used/implemented in practice: analysis of responses

[Tim Northover]

> 1. The performance gain from this on real programs is small. I will suggest
> that the total performance gain from optimisations that rely on exploiting
> undefined behaviour - let's call them monkey's paw optimisations for short -
> is practically never more than a few percent, and often less than one
> percent.
>
> 2. For most programs, having the program work is worth far more than having
> it run a few percent faster.

Which may or may not be fine until you decide to switch
compilers/platforms. Encouraging programmers to use Clang-specific
interpretations of these constructs would promote vendor lock-in and
be a blow for portability, which I think is worse than UB. At least
now we can tell people "you're doing it wrong".

Cheers.

Tim.