On Tue, Jan 07, 2014 at 01:51:00PM +0100, Florian Weimer wrote:
> +static bool
> +stack_protect_return_slot_p ()
> +{
> + basic_block bb;
> +
> + FOR_ALL_BB_FN (bb, cfun)
> + for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
> + !gsi_end_p (gsi); gsi_next (&gsi))
> + {
> + gimple stmt = gsi_stmt (gsi);
> + if (is_gimple_call (stmt) && gimple_call_return_slot_opt_p (stmt))
I have to repeat, this is not the right test, it really is just an
optimization hint, nothing else. Just look where it is set (unless it is
C++ where some NRV is performed in the FE as mandated by the languages)
- in pass_return_slot, which is an optimization pass, not run with -O0 or
-Og at all. So, you'd stack protect something only if not -O0 or -Og, that
is just wrong, and only if it was suitable for NRV. You really want to
protect all functions that call something that is returned by hidden
reference.
Jakub
