Hi Jason,
On 8 Jan 2025, at 22:56, 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.
That’d be more future-proof for sure. I can work on this change for
GCC 16 if there’s consensus it’s the right thing to do.
> Patrick, what do you think?
>
>> gcc/testsuite/ChangeLog:
>>
>> * g++.dg/diagnostic/incomplete-type-2.C: New test.
>> * g++.dg/diagnostic/incomplete-type-2a.C: New test.
>>
>> ---
>> gcc/cp/cp-tree.h | 1 +
>> gcc/cp/error.cc | 2 +-
>> gcc/cp/typeck2.cc | 6 ++++++
>> gcc/testsuite/g++.dg/diagnostic/incomplete-type-2.C | 7 +++++++
>> .../g++.dg/diagnostic/incomplete-type-2a.C | 13
>> +++++++++++++
>> 5 files changed, 28 insertions(+), 1 deletion(-)
>> create mode 100644
>> gcc/testsuite/g++.dg/diagnostic/incomplete-type-2.C
>> create mode 100644
>> gcc/testsuite/g++.dg/diagnostic/incomplete-type-2a.C
>>
>> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
>> index 6de8f64b5ee..52f954b63d9 100644
>> --- a/gcc/cp/cp-tree.h
>> +++ b/gcc/cp/cp-tree.h
>> @@ -7297,6 +7297,7 @@ struct decl_location_traits
>> typedef hash_map<tree, location_t, decl_location_traits>
>> erroneous_templates_t;
>> extern GTY((cache)) erroneous_templates_t *erroneous_templates;
>> +extern tree get_current_template ();
>> extern bool cp_seen_error ();
>> #define seen_error() cp_seen_error ()
>> diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc
>> index 8c0644fba7e..7fd03dd6d12 100644
>> --- a/gcc/cp/error.cc
>> +++ b/gcc/cp/error.cc
>> @@ -197,7 +197,7 @@ class cxx_format_postprocessor : public
>> format_postprocessor
>> /* Return the in-scope template that's currently being parsed, or
>> NULL_TREE otherwise. */
>> -static tree
>> +tree
>> get_current_template ()
>> {
>> if (scope_chain && in_template_context && !current_instantiation
>> ())
>> diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
>> index fce687e83b3..505c143dae7 100644
>> --- a/gcc/cp/typeck2.cc
>> +++ b/gcc/cp/typeck2.cc
>> @@ -273,6 +273,12 @@ cxx_incomplete_type_inform (const_tree type)
>> if (!TYPE_MAIN_DECL (type))
>> return;
>> + /* When processing a template declaration body, the error
>> generated by the
>> + caller (if any) might have been suppressed by
>> -Wno-template-body. If that
>> + is the case, suppress the inform as well. */
>> + if (!warn_template_body && get_current_template ())
>> + return;
>> +
>> location_t loc = DECL_SOURCE_LOCATION (TYPE_MAIN_DECL (type));
>> tree ptype = strip_top_quals (CONST_CAST_TREE (type));
>> diff --git a/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2.C
>> b/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2.C
>> new file mode 100644
>> index 00000000000..e2fb20a4ae8
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2.C
>> @@ -0,0 +1,7 @@
>> +// PR c++/118163
>> +// { dg-do "compile" }
>> +
>> +template<class T>
>> +struct S { // { dg-note "until the closing brace" }
>> + S s; // { dg-error "has incomplete type" }
>> +};
>> diff --git a/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2a.C
>> b/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2a.C
>> new file mode 100644
>> index 00000000000..d13021d0b68
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/diagnostic/incomplete-type-2a.C
>> @@ -0,0 +1,13 @@
>> +// PR c++/118163
>> +// { dg-do "compile" }
>> +// { dg-additional-options "-Wno-template-body" }
>> +
>> +template<class T>
>> +struct S { // { dg-bogus "until the closing brace" }
>> + S s; // { dg-bogus "has incomplete type" }
>> +};
>> +
>> +// Check that we don't suppress errors outside of the body.
>> +struct forward_decl; // { dg-note "forward declaration" }
>> +template<class T>
>> +void foo (forward_decl) {} // { dg-error "has incomplete type" }
