On 03/23/2014 09:52 PM, Colomban Wendling wrote: > Le 24/03/2014 02:11, David Marceau a écrit : >> On 03/23/2014 08:36 PM, Joël Krähemann wrote: >>> >>> The following will compile but is it still correct? >>> >>> g_atomic_pointer_set(&(returnable_thread->safe_data), >>> NULL); >> http://developer.gimp.org/api/2.0/glib/glib-Basic-Types.html#gpointer >> typedef void* gpointer; >> >> http://developer.gimp.org/api/2.0/glib/glib-Atomic-Operations.html >> void g_atomic_pointer_set (volatile gpointer *atomic, gpointer newval); My bad: volatile void* * Colomban is correct. > > That's not the signature in current GLib, but that's actually correct, > and means: > > void g_atomic_pointer_set (volatile void* *atomic, gpointer newval); > > hence, pointer to pointer. > >> struct _AgsReturnableThread >> { >> AgsThread thread; >> volatile guint flags; >> volatile void *safe_data; // volatile gpointer safe_data >> }; >> >> safe_data holds the address pointing to a void value(unassigned type). >> By putting &(blah->safe_data), you are asking for the address of the >> address pointing to a void value. That's not what you want. > > Yes it is. The atomic pointer functions expect a pointer to the pointer > to atomically set, not the pointer to set itself. > >> Just put (blah->safe_data, NULL). >> The compiler shouldn't complain. > > it shouldn't using a real function, but then it would crash at runtime. > Anyway, GLib has various compiler-specific implementation of the atomic > operations, and the GCC one uses macros, which will detect the > dereference of that pointer to void, which is invalid C. > > The macros does basically (a lot simplified): > > #define g_atomic_pointer_set(ptr, valure) \ > ({ \ > *(ptr) = (value); \ > __sync(); \ > }) > >> If it does, you could cast blah->safe_data with >> (volatile void*)(blah->safe_data) >> >> or >> >> (volatile gpointer)(blah->safe_data) > > That's not a wise idea in case it'd hide some real issue, nor of any > use, in C any pointer is a valid void*. And it wouldn't help here. > > Cheers, > Colomban > _______________________________________________ > gtk-app-devel-list mailing list > gtk-app-devel-list@gnome.org > https://mail.gnome.org/mailman/listinfo/gtk-app-devel-list >
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