Hi,
On 14 Jan 2025, at 2:56, Jason Merrill wrote:
> On 1/12/25 2:39 PM, Simon Martin wrote:
>> [ Fixing David’s email address :-/ ]
>>
>> Hi,
>>
>> On 9 Jan 2025, at 20:08, Simon Martin wrote:
>>
>>> On 9 Jan 2025, at 20:00, Marek Polacek wrote:
>>>
>>>> On Thu, Jan 09, 2025 at 12:05:43PM -0500, Patrick Palka wrote:
>>>>> On Wed, 8 Jan 2025, Jason Merrill wrote:
>>>>>
>>>>>> On 12/21/24 11:35 AM, Simon Martin wrote:
>>>>>>> When erroring out due to an incomplete type, we add a contextual
>>>>>>> note
>>>>>>> about the type. However, when the error is suppressed by
>>>>>>> -Wno-template-body, the note remains, making the compiler output
>>>>>>> quite
>>>>>>> puzzling.
>>>>>>>
>>>>>>> This patch makes sure the note is suppressed if we're processing
>>>>>>> a
>>
>>>>>>> template declaration body with -Wno-template-body.
>>>>>>>
>>>>>>> Successfully tested on x86_64-pc-linux-gnu.
>>>>>>>
>>>>>>> PR c++/118163
>>>>>>>
>>>>>>> gcc/cp/ChangeLog:
>>>>>>>
>>>>>>> * cp-tree.h (get_current_template): Declare.
>>>>>>> * error.cc (get_current_template): Make non static.
>>>>>>> * typeck2.cc (cxx_incomplete_type_inform): Suppress note when
>>>>>>> parsing a template declaration with -Wno-template-body.
>>>>>>
>>>>>> I think rather than adding this sort of thing in lots of places
>>>>>> where an error
>>>>>> is followed by an inform, we should change error to return bool
>>>>>> like
>>>>>> other
>>>>>> diagnostic functions, and check its return value before calling
>>>>>> cxx_incomplete_type_inform or plain inform. This likely involves
>>>>>> the same
>>>>>> number of changes, but they should be smaller.
>>>>>>
>>>>>> Patrick, what do you think?
>>>>>
>>>>> That makes sense to me, it's consistent with the 'warning' API and
>>>>> how
>>>>> we handle issuing a warning followed by a note. But since the
>>>>> -Wtemplate-body mechanism is really only useful for compiling
>>>>> legacy
>>
>>>>> code where you don't really care about any diagnostics anyway, and
>>>>> the intended way to use it is -fpermissive /
>>>>> -Wno-error=template-body
>>>>> rather than -Wno-template-body, I'd prefer a less invasive
>>>>> solution
>>>>> that
>>>>> doesn't change the API of 'error' if possible.
>>>>>
>>>>> I wonder if we can work around this by taking advantage of the
>>>>> fact
>>>>> that
>>>>> notes that follow an error are expected to be linked via an active
>>>>> auto_diagnostic_group? Roughly, if we issued a -Wtemplate-body
>>>>> diagnostic from an active auto_diagnostic_group then all other
>>>>> diagnostics from that auto_diagnostic_group should also be
>>>>> associated
>>>>> with -Wtemplate-body, including notes. That way
>>>>> -Wno-template-body
>>>>> will
>>>>> effectively suppress subsequent notes followed by an eligible
>>>>> error,
>>
>>>>> and
>>>>> no 'error' callers need to be changed (unless to use
>>>>> auto_diagnostic_group).
>>>>
>>>> FWIW, I love this auto_diagnostic_group idea.
>>> Thanks folks, I’ll explore the auto_diagnostic_group idea (and
>>> maybe
>>> *also* the error returning bool one because I am not a fan of
>>> functions
>>> that “lie” to their callers :-))
>>>
>>> I’ll send a follow-up patch in the coming days.
>> Please find attached an updated version of the patch, that implements
>>
>> Patrick’s idea and fixes both PR118163 and PR118392. It tracks the
>> depth at which a warning is inhibited, and suppresses all the notes
>> from
>> that depth on until an error/warning is emitted or that depth is
>> left.
>>
>> Successfully tested on x86_64-pc-linux-gnu. OK for GCC 16?
>
>> + int curr_depth = (m_diagnostic_groups.m_group_nesting_depth
>> + + m_diagnostic_groups.m_diagnostic_nesting_level);
>
> Do we care about the nesting level? I'd lean toward ignoring it and
> only considering the group.
We sort of do, unfortunately: I initially only considered the group, but
this breaks (at least) initlist-ctor1.C, where the following happens:
1. print_error_for_call_failure, with its auto_diagnostic_group, calls
print_z_candidates wants to print 4 candidates
At this stage, m_group_nesting_depth == 1,
m_diagnostic_nesting_level == 0
2. For candidate #1,
a. print_z_candidate uses a auto_diagnostic_nesting_level sentinel,
that increases the nesting level
b. print_conversion_rejection is called
At this stage, m_group_nesting_depth == 1,
m_diagnostic_nesting_level == 1
and calls perform_implicit_conversion
At this stage, m_group_nesting_depth == 1,
m_diagnostic_nesting_level == 3 !!!!
which calls convert_like_internal
3. For all subsequent candidates, the notes are suppressed
Simon
