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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/102377] New: FAIL:
 29_atomics/atomic_flag/cons/56012.cc with -std=gnu++20
Date: Thu, 16 Sep 2021 19:19:40 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102377

            Bug ID: 102377
           Summary: FAIL: 29_atomics/atomic_flag/cons/56012.cc with
                    -std=3Dgnu++20
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
                CC: rodgertq at gcc dot gnu.org
  Target Milestone: ---

In file included from
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_base.h:41,^M
                 from
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/atomic=
:41,^M
                 from
/home/jwakely/src/gcc/gcc/libstdc++-v3/testsuite/29_atomics/atomic_flag/con=
s/56012.cc:21:^M
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
warning: use of 'std::hardware_destructive_interference_size'
[-Winterference-size]^M
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
note: its value can vary between compiler versions or with different '-mtun=
e'
or '-mcpu' flags^M
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
note: if this use is part of a public ABI, change it to instead use a const=
ant
variable you define^M
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
note: the default value for the current CPU tuning is 64 bytes^M
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
note: you can stabilize this value with '--param
hardware_destructive_interference_size=3D64', or disable this warning with
'-Wno-interference-size'^M
FAIL: 29_atomics/atomic_flag/cons/56012.cc (test for excess errors)
Excess errors:
/home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/a=
tomic_wait.h:194:
warning: use of 'std::hardware_destructive_interference_size'
[-Winterference-size]


This is because <bits/atomic_wait.h> uses
hardware_destructive_interference_size, which we probably don't want to do =
in
the library headers.=