On Tue, Sep 09, 2025 at 02:58:58PM +0000, Qing Zhao wrote:
> Just briefly checked the v2, I have the following question:
>
> There is no change to the routine expand_DEFERRED_INIT for the new “init_type
> == AUTO_INIT_CXX26”,
> Is this intentional?
Yes. I've checked and all the checks during the expansion were checking for
init_type == AUTO_INIT_PATTERN, so AUTO_INIT_CXX26 behaves like
AUTO_INIT_ZERO.
> If yes, then the new init_type AUTO_INIT_CXX26 will be treated as
> AUTO_INIT_ZERO when expanding
> the call to .DEFERRED_INIT (size, init_type, …), i.e, the variable will be
> zero-initialized.
>
> Is this expected behavior?
Yes. The intent is that -std=c++26 without explicit
-ftrivial-auto-var-init= behaves as zero except for no extra
__builtin_clear_padding calls. So -ftrivial-auto-var-init=unitialized
-std=c++26 would in particular keep the C++23 behavior for projects which
can't afford the slowdowns and don't want [[indeterminate]] everywhere.
Jakub
