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From: "jamessan at jamessan dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/95676] New: [armhf] g++ mis-compiles code at -O1 or above
Date: Mon, 15 Jun 2020 04:33:17 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95676

            Bug ID: 95676
           Summary: [armhf] g++ mis-compiles code at -O1 or above
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamessan at jamessan dot com
  Target Milestone: ---

Created attachment 48730
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D48730&action=3Dedit
Reduced test case

After uploading msgpack-c 3.3.0 to Debian, the armhf build failed due to a
specific test failing.  I originally reported this to msgpack-c's upstream:
https://github.com/msgpack/msgpack-c/issues/881

However, after testing on Debian's porterbox, it seems to be a GCC issue.  =
The
issue does not reproduce when compiled with -O0 but does with -O1 or higher.

Similarly, changing the line that was failing from using googletest's
"EXPECT_TRUE(foo =3D=3D bar);" to "EXPECT_EQ(foo, bar);" caused the test to=
 pass.

I was able to use creduce to produce the attached file, test.cpp, which
exhibits the problem.  The final assignment in main (cd =3D ce.aq<ba::z::bw=
>() =3D=3D
g;) should always evaluate to true.=