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Re: Help in tracking down unusual apparent 5.2.0 LTO issue
- From: Markus Trippelsdorf <markus at trippelsdorf dot de>
- To: Matt Godbolt <matt at godbolt dot org>
- Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
- Date: Thu, 17 Mar 2016 18:03:13 +0100
- Subject: Re: Help in tracking down unusual apparent 5.2.0 LTO issue
- Authentication-results: sourceware.org; auth=none
- References: <CAFWXXN0fD0JXwt66dVz8=JPvH6V+w43uO9G5ASNg3MNEf6aA2w at mail dot gmail dot com> <CAFWXXN2Cz0p-1uCPPg6xxKz0HdEz6Mbh7SzvoeLrpbL+THXe+Q at mail dot gmail dot com> <CAFWXXN0fi92MD=ZimWpj+oeK+g3tV5rNKEnpbfnO62UEimYqUg at mail dot gmail dot com> <20160317134222 dot GA311 at x4> <CAFWXXN247A7rJYe2r91urOOBOv4d2GW7nCvSZgKd0S=AgHpchw at mail dot gmail dot com> <CAFWXXN0wEuUTQJci9g+oX-D43_cOkJH=gQBHw=VgKR4O8YaoeA at mail dot gmail dot com> <20160317161735 dot GB311 at x4> <CAFWXXN3sgPr+kVjZ=dv5VzMKBoLxYiYpaiJQejy4nPuZATMqjw at mail dot gmail dot com>
On 2016.03.17 at 11:50 -0500, Matt Godbolt wrote:
> Hi,
>
> I confirmed we're passing -std=c++1y in both cases (yes; this has
> bitten us before so we're sensitive to this! :). That said; I believe
> the list ABI change was guarded with new namespaces (as was the
> std::string changes that came alongside).
>
> There's no ODR violations that we can find. We build with -Wall
> -Wextra -Werror and have seen ODR errors reported during LTO before,
> but do not have any in this project. We run (a debug version) with
> -fsanitize=undefined (or at least a subset of undefined behaviour),
> and that's clean. The subset does not include "taking reference to a
> null pointer" as this is something parts of our code do. (None
> involving std::function or any lists).
Hmm, this sounds like -fno-delete-null-pointer-checks may help.
--
Markus