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From: "sjames at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/111904] New: Miscompilation with -O3
 -fharden-control-flow-redundancy?
Date: Fri, 20 Oct 2023 22:25:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111904

            Bug ID: 111904
           Summary: Miscompilation with -O3
                    -fharden-control-flow-redundancy?
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
                CC: aoliva at gcc dot gnu.org
  Target Milestone: ---

Created attachment 56161
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D56161&action=3Dedit
memset_explicit-gone-wrong.tar.xz

Needs a trunk build from today or newer for -fharden-control-flow-redundanc=
y.

1. git clone https://git.savannah.gnu.org/git/gnulib.git
2. ./gnulib-tool --single-configure --conditional-dependencies --create-tes=
tdir
--dir=3Duhoh memset_explicit
3. cd uhoh
4. ./configure CFLAGS=3D"-O3 -fharden-control-flow-redundancy" # passes wit=
h -O2
5. make TESTS=3Dtest-memset_explicit check -j$(nproc)

```
$ ./test-memset_explicit
test_heap: address range is still mapped after free().
test_stack: count =3D 1000
test-memset_explicit.c:191: assertion 'count < 50' failed
Aborted (core dumped)
```

I'm not sure where it goes wrong yet. Attached
memset_explicit-gone-wrong.tar.xz has uhoh-O2 (good) and uhoh-O3 (bad) for
x86_64, but I reproduced this on arm64 too.=