hfinkel added a subscriber: hfinkel.
hfinkel added a comment.

In http://reviews.llvm.org/D18823#397071, @rengolin wrote:

> En passant comment: I really wish we wouldn't.
>
> The C++ standard had some very careful considerations on VLAs and decided 
> *not* to support. It wasn't for lack of interest, it was a well informed 
> decision.


The decision might have been well informed, but it was really a lack of 
consensus. There was (and still is) a large fraction of the committee in favor 
of VLAs (or ARBs as they called them). There is also a large fraction of the 
committee opposed to them, or willing to accept them, but only if we could also 
add a library type with a better interface. There is a concern, which is not 
completely unreasonable, that if we make a point of adding this feature to the 
C++ standard, without adding a library container type, it will make people more 
likely to use "raw" arrays and pointers instead of using higher-level 
containers and iterators. It turns out, however, that it is not clear how such 
a library container could be implemented in practice.

However, as an implementation extension, this concern is not relevant. I'm in 
favor of this; I have uses who use this feature in GCC. It is certainly true 
that most HPC users are using these on PODs, but the fact that you cannot apply 
them to other types creates a problem with generic programming that people have 
run into.


http://reviews.llvm.org/D18823



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