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From: "npl at chello dot at" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/65945] New: ARM: unaligned access when stroing nullptr
Date: Thu, 30 Apr 2015 10:08:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65945

            Bug ID: 65945
           Summary: ARM: unaligned access when stroing nullptr
           Product: gcc
           Version: 4.8.4
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: npl at chello dot at
  Target Milestone: ---

Created attachment 35429
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35429&action=edit
code causing the issue

Hello,

the attachedcode produces an unaligned access for arm, on the production code I
ran into this issue with versions 5.1, 4.9.2, 4.8.4. This reduced testcase
doesnt produce the issue with 5.1, but for 4.9.2 and 4.8.4.

The issue seems to be the line
constexpr inline_type bool operator ==(bitmask X, decltype(nullptr)) \
{ return X == bitmask(); }

aparrently gcc converts stores the given parameter on the frame without caring
for alignment ("str      r3, [fp, #-25]"). changing the type to unsigned seems
to fix this

Commandline to reproduce:
arm-none-eabi-g++ -std=c++11 -O0 -c unalignedgcc.cpp