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From: "fxcoudert at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/106435] New: constructor of thread_local static member
 is not called
Date: Mon, 25 Jul 2022 16:37:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106435

            Bug ID: 106435
           Summary: constructor of thread_local static member is not
                    called
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxcoudert at gcc dot gnu.org
  Target Milestone: ---

Originally reported to Homebrew at
https://github.com/Homebrew/homebrew-core/issues/105022



$ cat foo.hpp=20
#pragma once

struct Foo {
  Foo();
  void func();
};

struct Bar {
  thread_local static Foo foo;
};

$ cat foo.cpp=20
#include "foo.hpp"

#include <iostream>

Foo::Foo() {
  std::cout << "Foo::Foo(this=3D" << this << ")\n";
}

void Foo::func() {
  std::cout << "Foo::func(this=3D" << this << ")\n";
}

thread_local Foo Bar::foo;

$ cat main.cpp=20
#include "foo.hpp"

int main() {
  Bar::foo.func();
}


Compiled with clang, the constructor is called. Compiled with gcc 11 or 12 =
on
aarch64-apple-darwin21, it is not:


$ g++-12 -std=3Dc++17 foo.cpp main.cpp && ./a.out=20=20=20=20=20=20=20=20=
=20=20=20
Foo::func(this=3D0x6000009e0038)
$ g++-11 -std=3Dc++17 foo.cpp main.cpp && ./a.out
Foo::func(this=3D0x600001418038)
$ clang++ -std=3Dc++17 foo.cpp main.cpp && ./a.out
Foo::Foo(this=3D0x60000209c000)
Foo::func(this=3D0x60000209c000)


$ g++-12 -v=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
Using built-in specs.
COLLECT_GCC=3Dg++-12
COLLECT_LTO_WRAPPER=3D/opt/homebrew/Cellar/gcc@12/12.1.0_1/bin/../libexec/g=
cc/aarch64-apple-darwin21/12/lto-wrapper
Target: aarch64-apple-darwin21
Configured with: ../configure --prefix=3D/opt/homebrew/opt/gcc@12
--libdir=3D/opt/homebrew/opt/gcc@12/lib/gcc/12 --disable-nls
--enable-checking=3Drelease --with-gcc-major-version-only
--enable-languages=3Dc,c++,objc,obj-c++,fortran --program-suffix=3D-12
--with-gmp=3D/opt/homebrew/opt/gmp --with-mpfr=3D/opt/homebrew/opt/mpfr
--with-mpc=3D/opt/homebrew/opt/libmpc --with-isl=3D/opt/homebrew/opt/isl
--with-zstd=3D/opt/homebrew/opt/zstd --with-pkgversion=3D'Homebrew GCC 12.1=
.0_1'
--with-bugurl=3Dhttps://github.com/Homebrew/homebrew-core/issues
--with-system-zlib --build=3Daarch64-apple-darwin21
--with-native-system-header-dir=3D/usr/include
--with-sysroot=3D/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.1.0 (Homebrew GCC 12.1.0_1)=