The recent update to gnulib commit 9d7a37ecb2ab516c19164a57b8aeb32016a99d2c Author: Eric Blake <eblake(a)redhat.com&gt; Date: Thu Sep 15 15:12:52 2016 -0500 build: update to latest gnulib Pulled in a change that adds -fno-common to the default compiler flags commit bf8e658ffadb95d444f56d222d04c9af955af765 Author: Jim Meyering <meyering(a)fb.com&gt; Date: Fri Sep 2 09:16:16 2016 -0700 manywarnings: add -fno-common This caused libvirt Mingw build to break with the compiler reporting 100's of definitions of virConnectAuthPtrDefault ./.libs/libvirt_util.a(libvirt_util_la-virarch.o):virarch.c:(.bss+0x0): multiple definition of `virConnectAuthPtrDefault' ./.libs/libvirt_util.a(libvirt_util_la-viralloc.o):viralloc.c:(.bss+0x0): first defined here ./.libs/libvirt_util.a(libvirt_util_la-viratomic.o):viratomic.c:(.bss+0x0): multiple definition of `virConnectAuthPtrDefault' ./.libs/libvirt_util.a(libvirt_util_la-viralloc.o):/home/berrange/src/virt/libvirt/src/util/viralloc.c:87: first defined here ./.libs/libvirt_util.a(libvirt_util_la-viraudit.o):viraudit.c:(.bss+0x0): multiple definition of `virConnectAuthPtrDefault' ./.libs/libvirt_util.a(libvirt_util_la-viralloc.o):/home/berrange/src/virt/libvirt/src/util/viralloc.c:87: first defined here ./.libs/libvirt_util.a(libvirt_util_la-virauth.o):virauth.c:(.bss+0x0): multiple definition of `virConnectAuthPtrDefault' ./.libs/libvirt_util.a(libvirt_util_la-viralloc.o):/home/berrange/src/virt/libvirt/src/util/viralloc.c:87: first defined here ./.libs/libvirt_util.a(libvirt_util_la-virauthconfig.o):virauthconfig.c:(.bss+0x0): multiple definition of `virConnectAuthPtrDefault' ...snip... The cause is our VIR_EXPORT_VAR macro which has some magic on win to add dllexport/dllimport to the variable declaration. Unfortunately the dllexport branch missed off the 'extern' keyword, so the header file was in fact declaring an instance of the variable in every source file. Previously the linker would merge all these definitions into one, but that no longer happens due to -fno-common Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- Pushing as a CI build fix include/libvirt/libvirt-common.h.in | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/libvirt/libvirt-common.h.in b/include/libvirt/libvirt-common.h.in index 79bfe90..0e8ada4 100644 --- a/include/libvirt/libvirt-common.h.in +++ b/include/libvirt/libvirt-common.h.in @@ -49,7 +49,7 @@ extern "C" { # define VIR_EXPORT_VAR extern # else # ifdef IN_LIBVIRT -# define VIR_EXPORT_VAR __declspec(dllexport) +# define VIR_EXPORT_VAR __declspec(dllexport) extern # else # define VIR_EXPORT_VAR __declspec(dllimport) extern # endif -- 2.7.4