[llvm-dev] RFC: Extend UBSan with qsort checks
Paul Pluzhnikov via llvm-dev
llvm-dev at lists.llvm.org
Wed Jan 13 23:06:30 PST 2016
On Wed, Jan 13, 2016 at 10:37 PM, Yuri Gribov <tetra2005 at gmail.com> wrote:
> I'm afraid it's even N^3 (with N=32 cap). This indeed sounds scary but
> I have not seen significant slowdowns when running instrumented
> distro.
Have you looked at how many sort invocations there are, and what their
size distribution is?
Perhaps naively, I expect very few sort()s to be performed in day to
day distro operation, and even fewer sort()s with more than 20
elements.
> Right, I thought about improving this with testing random 32 elements
> instead of the first ones.
That has its own disadvantages: it makes the failure detection
non-repeatable, and makes it harder to understand the conditions under
which the predicate is broken.
--
Paul Pluzhnikov
More information about the llvm-dev
mailing list