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Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>

From: Marc Glisse <marc dot glisse at inria dot fr>
To: Jonathan Wakely <jwakely at redhat dot com>
Cc: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
Date: Thu, 28 May 2015 15:52:10 +0200 (CEST)
Subject: Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
Authentication-results: sourceware.org; auth=none
References: <20150528115330 dot GL2985 at redhat dot com> <alpine dot DEB dot 2 dot 11 dot 1505281522500 dot 11312 at stedding dot saclay dot inria dot fr> <20150528133817 dot GP2985 at redhat dot com> <20150528134042 dot GQ2985 at redhat dot com>
Reply-to: libstdc++ at gcc dot gnu dot org

On Thu, 28 May 2015, Jonathan Wakely wrote:

Would there be a danger of an object compiled with gcc-5.1 that calls
array<T, 0>::data() finding the _S_ref from an object compiled with
gcc-5.2 and hitting the __builtin_unreachable in vali code?

At -O0, maybe. To be safe you would need to give this _S_ref an arbitraryabi_tag. You could also replace all uses of _S_ref with *_S_ptr.


--
Marc Glisse

Follow-Ups:
- Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
  - From: Jonathan Wakely

References:
- [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
  - From: Jonathan Wakely
- Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
  - From: Marc Glisse
- Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
  - From: Jonathan Wakely
- Re: [patch] libstdc++/65352 fix ubsan errors in std::array<T, 0>
  - From: Jonathan Wakely

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