https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97729
--- Comment #4 from Markus Böck <markus.boeck02 at gmail dot com> --- Indeed that sounds like it might be the issue. I am currently on a very recent version of binutils: $ ./x86_64-w64-mingw32-ld --version GNU ld (GNU Binutils) 2.35.50.20200709 Copyright (C) 2020 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or (at your option) a later version. This program has absolutely no warranty. Changing the lines you posted above yields me a compiler error now: libtool: compile: /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/./gcc/xgcc -shared-libgcc -B/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/./gcc -nostdinc++ -L/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/src -L/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/src/.libs -L/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/libsupc++/.libs -L/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/lib -L/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/mingw/lib -isystem /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/include -isystem /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/mingw/include -B/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/bin/ -B/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/lib/ -isystem /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/include -isystem /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/x86_64-w64-mingw32/sys-include -I/mnt/c/GCC-Build-Array/gcc/libstdc++-v3/../libgcc -I/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/x86_64-w64-mingw32 -I/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include -I/mnt/c/GCC-Build-Array/gcc/libstdc++-v3/libsupc++ -I/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/install/include -std=gnu++11 -D_GLIBCXX_SHARED -fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi=2 -fdiagnostics-show-location=once -ffunction-sections -fdata-sections -frandom-seed=future.lo -Wno-error=format-extra-args -Wno-error=format -g1 -fdebug-prefix-map=/mnt/c=C: -c ../../../../../libstdc++-v3/src/c++11/future.cc -o future.o In file included from ../../../../../libstdc++-v3/src/c++11/future.cc:29: /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/future: In member function 'std::__future_base::_Result<_Res>& std::__basic_future<_Res>::_M_get_result() const': /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/future:712:30: error: ambiguous overload for 'operator==' (operand types are 'std::__exception_ptr::exception_ptr' and 'int') 712 | if (!(__res._M_error == 0)) | ~~~~~~~~~~~~~~ ^~ ~ | | | | | int | std::__exception_ptr::exception_ptr /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/future:712:30: note: candidate: 'operator==(std::__exception_ptr::exception_ptr::__safe_bool {aka void (std::__exception_ptr::exception_ptr::*)()}, std::__exception_ptr::exception_ptr::__safe_bool {aka void (std::__exception_ptr::exception_ptr::*)()})' (built-in) 712 | if (!(__res._M_error == 0)) | ~~~~~~~~~~~~~~~^~~~ In file included from /mnt/c/GCC-Build-Array/gcc/libstdc++-v3/libsupc++/exception:147, from /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/mutex:40, from /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/future:38, from ../../../../../libstdc++-v3/src/c++11/future.cc:29: /mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/include/bits/exception_ptr.h:223:5: note: candidate: 'bool std::__exception_ptr::operator==(const std::__exception_ptr::exception_ptr&, const std::__exception_ptr::exception_ptr&)' 223 | operator==(const exception_ptr&, const exception_ptr&) | ^~~~~~~~ Makefile:644: recipe for target 'future.lo' failed make[5]: Leaving directory '/mnt/c/GCC-Build-Array/gcc/build-host-x86_64/x86_64-w64-mingw32/libstdc++-v3/src/c++11'