Re: [Boost-bugs] [Boost C++ Libraries] #13109: Incorrect result when casting from multiprecision::uint128_t to unsigned long long.

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #13109: Incorrect result when casting from multiprecision::uint128_t to unsigned long long.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-12-30 18:17:48

#13109: Incorrect result when casting from multiprecision::uint128_t to unsigned
long long.
-------------------------------+----------------------------
  Reporter:  gvisser@…         |      Owner:  John Maddock
      Type:  Bugs              |     Status:  closed
 Milestone:  To Be Determined  |  Component:  multiprecision
   Version:  Boost 1.63.0      |   Severity:  Problem
Resolution:  fixed             |   Keywords:
-------------------------------+----------------------------
Changes (by John Maddock):

 * status:  new => closed
 * resolution:   => fixed

Comment:

 The intended behaviour is to return the maximum value of the target type
 when a narrowing conversion overflows (I realise this is different
 behaviour to most built in integer types, but then you're into undefined
 behaviour).

 This patch:
 https://github.com/boostorg/multiprecision/commit/b35f1c8f613db66ad80ce260f94b7027814ede71
 enforces uniform behaviour across all backend integer types.

 In future, if you really want just the low order N bits, then you will
 need to mask these out - the same is true of built in integers actually if
 you want to avoid code-sanitizer errors (cland usan etc).

-- 
Ticket URL: <https://svn.boost.org/trac10/boost/ticket/13109#comment:1>
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