Re: [PATCH] tests: Compile virgdbusmock.c with GIO_COMPILATION enabled
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.
Unfortunately, I also don't really have a better alternative to
suggest, so I guess it is what it is :)
--
Andrea Bolognani / Red Hat / Virtualization