https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123183
--- Comment #3 from Roger Orr <rogero at howzatt dot co.uk> --- I have very similar errors while trying to build gcc on cygwin on Windows using ../gcc-trunk/configure --enable-languages=c,c++ --enable-threads=posix It worked with da97de41f8837a9e1eea78ca049f50e105f909c8 on 2025-12-06 It fails with f129bfb6a81abd8dcf8ccc6e4b23813766d9fdb2 libtool: link: /cygdrive/c/Projects/gcc/build/./gcc/xgcc -shared-libgcc -B/cygdrive/c/Projects/gcc/build/./gcc -nostdinc++ -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/src -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/src/.libs -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/libsupc++/.libs -B/usr/share/gcc-trunk/x86_64-pc-cygwin/bin/ -B/usr/share/gcc-trunk/x86_64-pc-cygwin/lib/ -isystem /usr/share/gcc-trunk/x86_64-pc-cygwin/include -isystem /usr/share/gcc-trunk/x86_64-pc-cygwin/sys-include -fno-checking -shared -nostdlib /cygdrive/c/Projects/gcc/build/./gcc/crtbeginS.o .libs/compatibility.o .libs/compatibility-debug_list.o .libs/compatibility-debug_list-2.o .libs/compatibility-atomic-c++0x.o .libs/compatibility-c++0x.o .libs/compatibility-chrono.o .libs/compatibility-condvar.o .libs/compatibility-thread-c++0x.o -Wl,--whole-archive ../libsupc++/.libs/libsupc++convenience.a ../src/c++98/.libs/libc++98convenience.a ../src/c++11/.libs/libc++11convenience.a ../src/c++17/.libs/libc++17convenience.a ../src/c++20/.libs/libc++20convenience.a -Wl,--no-whole-archive -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/libsupc++/.libs -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/src -L/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/src/.libs -liconv -L/cygdrive/c/Projects/gcc/build/./gcc -L/lib -L/usr/lib -lgcc_s -lgcc -lcygwin -ladvapi32 -lshell32 -luser32 -lkernel32 -lgcc_s -lgcc /cygdrive/c/Projects/gcc/build/./gcc/crtend.o -Wl,-O1 -Wl,--gc-sections -Wl,--version-script=libstdc++-symbols.ver -o .libs/cygstdc++-6.dll -Wl,--enable-auto-image-base -Xlinker --out-implib -Xlinker .libs/libstdc++.dll.a /usr/lib/gcc/x86_64-pc-cygwin/14/../../../../x86_64-pc-cygwin/bin/ld: ../src/c++20/.libs/libc++20convenience.a(format.o): in function `_ZNSt9bad_allocD1Ev': /cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/include/bits/new_except.h:65: multiple definition of `_ZNSt9bad_allocD1Ev'; ../libsupc++/.libs/libsupc++convenience.a(bad_alloc.o):/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/libsupc++/../../../../gcc-trunk/libstdc++-v3/libsupc++/bad_alloc.cc:28: first defined here /usr/lib/gcc/x86_64-pc-cygwin/14/../../../../x86_64-pc-cygwin/bin/ld: ../src/c++20/.libs/libc++20convenience.a(format.o): in function `_ZNKSt9bad_alloc4whatEv': /cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/include/bits/new_except.h:70: multiple definition of `_ZNKSt9bad_alloc4whatEv'; ../libsupc++/.libs/libsupc++convenience.a(bad_alloc.o):/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/libsupc++/../../../../gcc-trunk/libstdc++-v3/libsupc++/bad_alloc.cc:34: first defined here /usr/lib/gcc/x86_64-pc-cygwin/14/../../../../x86_64-pc-cygwin/bin/ld: ../src/c++20/.libs/libc++20convenience.a(format.o): in function `_ZNSt9bad_allocD0Ev': /cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/include/bits/new_except.h:65: multiple definition of `_ZNSt9bad_allocD0Ev'; ../libsupc++/.libs/libsupc++convenience.a(bad_alloc.o):/cygdrive/c/Projects/gcc/build/x86_64-pc-cygwin/libstdc++-v3/libsupc++/../../../../gcc-trunk/libstdc++-v3/libsupc++/bad_alloc.cc:28: first defined here collect2: error: ld returned 1 exit status
