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From "Jim Apple (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] Add a build flag for the undefined behavior sanitizer, aka "ubsan".
Date Sun, 27 Nov 2016 01:59:06 GMT
Jim Apple has posted comments on this change.

Change subject: Add a build flag for the undefined behavior sanitizer, aka "ubsan".
......................................................................


Patch Set 1:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/5082/1/be/CMakeLists.txt
File be/CMakeLists.txt:

Line 40: #  -fwrapv: force signed integer arithmetic operations to wrap
> Mostly yes, although we don't use unsigned ints in many places in the codeb
Tim, if I understand you correctly, your POV is that:

A. Our code should not execute instructions that cause int overflow, usually.

B. -fwrapv may slow down the code.

C. The -fwrapv status should be the same in codegenned code paths and non-codegenned code
paths.

My POV is that:

1. We should care a great deal about preventing UB because the bugs it causes can be disastrous
(taking both branches of a conditional) and hard to repro.

Actually, that's mostly it; just #1. If I can remove any overflows from our testsuite using
UBSAN and show -fwrapv does not hurt our benchmarks and get codegenned code to use -fwrap
just like non-codegenned code can with just this flag, wold you be OK with using -fwrapv?


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Gerrit-MessageType: comment
Gerrit-Change-Id: I88c7234bd7c5eb7404490a0913d90470c10835e7
Gerrit-PatchSet: 1
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Jim Apple <jbapple-impala@apache.org>
Gerrit-Reviewer: Dan Hecht <dhecht@cloudera.com>
Gerrit-Reviewer: Jim Apple <jbapple-impala@apache.org>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-HasComments: Yes

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