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From: "ensadc at mailnesia dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/104919] New: [modules] enum in constexpr function causes
 "failed to read compiled module cluster 1: Bad file data"
Date: Mon, 14 Mar 2022 17:24:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104919

            Bug ID: 104919
           Summary: [modules] enum in constexpr function causes "failed to
                    read compiled module cluster 1: Bad file data"
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ensadc at mailnesia dot com
  Target Milestone: ---

https://godbolt.org/z/d3sdeEz1r

=3D=3D=3D=3D
$ cat mod.cpp
export module mod;

export constexpr void f() {
    enum { a };
    a;
}

$ cat example.cpp
import mod;

int main() {
    f();
}

$ g++ -std=3Dc++20 -fmodules-ts mod.cpp example.cpp
In module imported at example.cpp:1:1:
mod: In function =E2=80=98int main()=E2=80=99:
mod: error: failed to read compiled module cluster 1: Bad file data
mod: note: compiled module file is =E2=80=98gcm.cache/mod.gcm=E2=80=99
example.cpp:4:5: fatal error: failed to load binding =E2=80=98::f@mod=E2=80=
=99
    4 |     f();
      |     ^
compilation terminated.

=3D=3D=3D=3D
It compiles fine without `constexpr`.=