https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82134
Arne Vogel <arvo at me dot com> changed:
What |Removed |Added
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CC| |arvo at me dot com
--- Comment #4 from Arne Vogel <arvo at me dot com> ---
@Jakub Jelinek: Returning empty structs (this affects empty tuples as well) can
be useful in templates. E.g.
struct empty_t {};
template<typename C>
void executeContext()
{
auto savedState = C::prepare();
C::execute();
C::cleanup(std::move(savedState));
}
/*
* Context which does not require saving state but should be compatible
* with executeContext().
*/
struct StatelessContext
{
static empty_t prepare();
static void execute();
static void cleanup(empty_t);
};
// Usage: executeContext<StatelessContext>();
Obviously, void does not work here *precisely* because executeContext saves
(i.e. uses) the return value. I have an example that makes more sense than the
above, but takes longer to explain. Anyway, I hope you get the idea.
A possible workaround is e.g. to use a dummy char instead. The documentation
says (slightly misleadingly, see below) empty structs in G++ are treated as
though they contained a single char. But this in turn may cause unwanted
interference e.g. with empty base optimization.
