On 3/28/23 10:33, Andrea Bolognani wrote:
On Mon, Mar 27, 2023 at 02:47:40PM +0200, Michal Privoznik wrote:
There are couple of g_dbus_*() functions we provide an alternative implementation for in our virgdbusmock.c. However, these functions are declared in gio/gdbusconnection.h as:
GIO_AVAILABLE_IN_ALL GDBusConnection *g_bus_get_sync (GBusType bus_type, GCancellable *cancellable, GError **error);
where GIO_AVAILABLE_IN_ALL is declared as (in /gio/gio-visibility.h):
#if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(GIO_STATIC_COMPILATION) # define _GIO_EXPORT __declspec(dllexport) # define _GIO_IMPORT __declspec(dllimport) #elif __GNUC__ >= 4 # define _GIO_EXPORT __attribute__((visibility("default"))) # define _GIO_IMPORT #else # define _GIO_EXPORT # define _GIO_IMPORT #endif #ifdef GIO_COMPILATION # define _GIO_API _GIO_EXPORT #else # define _GIO_API _GIO_IMPORT #endif
#define _GIO_EXTERN _GIO_API extern
#define GIO_AVAILABLE_IN_ALL _GIO_EXTERN
Now, on mingw the functions we mock are declared with dllimport attribute which makes the compiler unhappy:
../tests/virgdbusmock.c:25:24: error: 'g_bus_get_sync' redeclared without dllimport attribute: previous dllimport ignored [-Werror=attributes]
The solution is to do what glib does when it compiles the gio module: set GIO_COMPILATION macro which in turn annotates the function with dllexport attribute.
I will point out that GIO_COMPILATION is not intended to be used outside of GLib: it signals that the gio module is in the process of being built, which can result (as is the case here) in different behavior compared to what you'd see when building *against* gio.
So defining it as part of building libvirt is quite yucky, and I wouldn't be surprised if this trick stopped working or ended up causing other unintended consequences in the future.
That's something we're already used to since switching to glib. This but another quirk that we have to deal with.
Unfortunately, I also don't really have a better alternative to suggest, so I guess it is what it is :)
Maybe don't build mocks on mingw? Do they even work, or better: can they? Michal