Re: [MirageOS-devel] unsigned integers

[Hannes Mehnert <hannes@xxxxxxxxxxx>]

On 07/09/2016 15:08, Anil Madhavapeddy wrote:
> I'd prefer to allocate and have a good API, but then I would also prefer to 
> not use compiler builtins that may introduce subtle optimisation bugs in the 
> future -- or at least until we know that the optimisations are useful.
> 
> E.g. the double fetch vulnerabilities that emerged from compiler builtins 
> https://xenbits.xen.org/xsa/advisory-155.html (not directly applicable here, 
> but my point is that I'd prefer a slightly slower but more consistent first 
> cut at this library)

I don't see the relation between builtins and compiler optimisations,
but I might lack knowledge about the bug.  Looking into some patches,
such as
https://xenbits.xen.org/xsa/xsa155-linux43-0005-xen-blkback-read-from-indirect-descriptors-only-once.patch
it has not much to do with builtins.

My first cut of this library was to use the builtins, since they're
available on all platforms I care about, but then Travis CI turned to be
unhappy (since it seems most Linux distributions ship arcane versions of
gcc).


hannes

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