Hi Folks
> On 8 Jul 2024, at 20:57, Jason Merrill <ja...@redhat.com> wrote:
>
> On 7/8/24 3:37 PM, Iain Sandoe wrote:
>>> On 8 Jul 2024, at 20:19, Jason Merrill <ja...@redhat.com> wrote:
>>>
>>> On 6/17/24 8:15 AM, Iain Sandoe wrote:
>>>> potentially_transformed_function_body ();
>>>> }
>>>> finally
>>>> {
>>>> handle_post_condition_checking ();
>>>> }
>>>> else [only if the function is not marked noexcept(true) ]
>>>> {
>>>> __rethrow ();
>>>
>>> This sounds undesirable, EH normally continues unwinding after running a
>>> cleanup. Why would the exception be considered caught in a way that needs
>>> a rethrow?
>> We need to implement that the no-EH cleanup [i.e. the postcondition] does
>> _not_ run when an exception is thrown. Right now there’s no HANDLER type
>> that does that - we have EH_ONLY but no NON_EH one (otherwise I'd have built
>> a C++ try).
>> however, I could not figure out how to make this arm of the EH_ELSE_EXPR
>> work as an empty construct (the gimplifier does not seem to expect this).
>
> You can't just put void_node in the else arm?
I had tried a number of permutations (void_node, empty_stmt, empty statement
list etc). Unfortunately, at present that causes the EH_ELSE expression to be
silently dropped in gimplication. The fact that you think it should work (as
did i) makes me think either we have a gimplifier bug or a misunderstanding:
@Alex;
we have (gcc/gimplify.cc:18423):
if (!gimple_seq_empty_p (n) && !gimple_seq_empty_p (e))
{
geh_else *stmt = gimple_build_eh_else (n, e);
gimple_seq_add_stmt (&cleanup, stmt);
}
Which essentially says “if either of the sub-expressions to this are empty,
then do not build it”
Was there a reason for this, or is it a typo?
If I replace ‘&&' by ‘||' (i.e. “if either of the sub-expressions is present,
then build it” then things behave as I expect.
IMO it the current action _is_ intended
(a) it should at least emit a checking diagnostic
(b) we need to figure out how to extend it so that we can implement what’s
needed (non-EH only cleanups)
So I patched the gimplifier as above and initial testing says that this change
does not cause any C++ regressions - but I need to do Ada, Objective-C etc too.
thoughts?
thanks
Iain
