* [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
@ 2023-03-01 20:33 Marek Polacek
2023-03-01 21:30 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Marek Polacek @ 2023-03-01 20:33 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
-Wmismatched-tags warns about the (harmless) struct/class mismatch.
For, e.g.,
template<typename T> struct A { };
class A<int> a;
it works by adding A<T> to the class2loc hash table while parsing the
class-head and then, while parsing the elaborate type-specifier, we
add A<int>. At the end of c_parse_file we go through the table and
warn about the class-key mismatches. In this PR we crash though; we
have
template<typename T> struct A {
template<typename U> struct W { };
};
struct A<int>::W<int> w; // #1
where while parsing A and #1 we've stashed
A<T>
A<T>::W<U>
A<int>::W<int>
into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
OK not to have found A<int>::W<U>, we should just look one "level" up,
that is, A<T>::W<U>.
It's important to handle class specializations, so e.g.
template<>
struct A<char> {
template<typename U>
class W { };
};
where W's class-key is different than in the primary template above,
so we should warn depending on whether we're looking into A<char>
or into a different instantiation.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/106259
gcc/cp/ChangeLog:
* parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
lookup of SPEC didn't find anything, try to look for
most_general_template.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wmismatched-tags-11.C: New test.
---
gcc/cp/parser.cc | 30 +++++++++++++++----
.../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
2 files changed, 47 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 1a124f5395e..b528ee7b1d9 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
be (and inevitably is) at index zero. */
tree spec = specialization_of (type);
cdlguide = class2loc.get (spec);
+ /* It's possible that we didn't find SPEC. Consider:
+
+ template<typename T> struct A {
+ template<typename U> struct W { };
+ };
+ struct A<int>::W<int> w; // #1
+
+ where while parsing A and #1 we've stashed
+ A<T>
+ A<T>::W<U>
+ A<int>::W<int>
+ into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
+ will yield A<int>::W<U> which may be in CLASS2LOC if we had
+ an A<int> class specialization, but otherwise won't be in it.
+ So try to look up A<T>::W<U>. */
+ if (!cdlguide)
+ {
+ spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
+ cdlguide = class2loc.get (spec);
+ }
+ /* Now we really should have found something. */
gcc_assert (cdlguide != NULL);
}
- else
- {
- /* Skip declarations that consistently use the same class-key. */
- if (def_class_key != none_type)
- return;
- }
+ /* Skip declarations that consistently use the same class-key. */
+ else if (def_class_key != none_type)
+ return;
/* Set if a definition for the class has been seen. */
const bool def_p = cdlguide->def_p ();
diff --git a/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C b/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
new file mode 100644
index 00000000000..6c4e571726a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
@@ -0,0 +1,23 @@
+// PR c++/106259
+// { dg-do compile }
+// { dg-options "-Wmismatched-tags" }
+
+template<typename T> struct A {
+ template<typename U>
+ struct W { };
+};
+
+template<>
+struct A<char> {
+ template<typename U>
+ class W { };
+};
+
+void
+g ()
+{
+ struct A<char>::W<int> w1; // { dg-warning "mismatched" }
+ struct A<int>::W<int> w2;
+ class A<char>::W<int> w3;
+ class A<int>::W<int> w4; // { dg-warning "mismatched" }
+}
base-commit: 096f034a8f5df41f610e62c1592fb90a3f551cd5
--
2.39.2
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
2023-03-01 20:33 [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259] Marek Polacek
@ 2023-03-01 21:30 ` Jason Merrill
2023-03-01 21:40 ` Marek Polacek
0 siblings, 1 reply; 6+ messages in thread
From: Jason Merrill @ 2023-03-01 21:30 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 3/1/23 15:33, Marek Polacek wrote:
> -Wmismatched-tags warns about the (harmless) struct/class mismatch.
> For, e.g.,
>
> template<typename T> struct A { };
> class A<int> a;
>
> it works by adding A<T> to the class2loc hash table while parsing the
> class-head and then, while parsing the elaborate type-specifier, we
> add A<int>. At the end of c_parse_file we go through the table and
> warn about the class-key mismatches. In this PR we crash though; we
> have
>
> template<typename T> struct A {
> template<typename U> struct W { };
> };
> struct A<int>::W<int> w; // #1
>
> where while parsing A and #1 we've stashed
> A<T>
> A<T>::W<U>
> A<int>::W<int>
> into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
> is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
> is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
> OK not to have found A<int>::W<U>, we should just look one "level" up,
> that is, A<T>::W<U>.
>
> It's important to handle class specializations, so e.g.
>
> template<>
> struct A<char> {
> template<typename U>
> class W { };
> };
>
> where W's class-key is different than in the primary template above,
> so we should warn depending on whether we're looking into A<char>
> or into a different instantiation.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> PR c++/106259
>
> gcc/cp/ChangeLog:
>
> * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
> lookup of SPEC didn't find anything, try to look for
> most_general_template.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/Wmismatched-tags-11.C: New test.
> ---
> gcc/cp/parser.cc | 30 +++++++++++++++----
> .../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
> 2 files changed, 47 insertions(+), 6 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
>
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index 1a124f5395e..b528ee7b1d9 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
> be (and inevitably is) at index zero. */
> tree spec = specialization_of (type);
> cdlguide = class2loc.get (spec);
> + /* It's possible that we didn't find SPEC. Consider:
> +
> + template<typename T> struct A {
> + template<typename U> struct W { };
> + };
> + struct A<int>::W<int> w; // #1
> +
> + where while parsing A and #1 we've stashed
> + A<T>
> + A<T>::W<U>
> + A<int>::W<int>
> + into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
> + will yield A<int>::W<U> which may be in CLASS2LOC if we had
> + an A<int> class specialization, but otherwise won't be in it.
> + So try to look up A<T>::W<U>. */
> + if (!cdlguide)
> + {
> + spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
Would it make sense to only look at most_general_template, not
A<int>::W<U> at all?
> + cdlguide = class2loc.get (spec);
> + }
> + /* Now we really should have found something. */
> gcc_assert (cdlguide != NULL);
> }
> - else
> - {
> - /* Skip declarations that consistently use the same class-key. */
> - if (def_class_key != none_type)
> - return;
> - }
> + /* Skip declarations that consistently use the same class-key. */
> + else if (def_class_key != none_type)
> + return;
>
> /* Set if a definition for the class has been seen. */
> const bool def_p = cdlguide->def_p ();
> diff --git a/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C b/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
> new file mode 100644
> index 00000000000..6c4e571726a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
> @@ -0,0 +1,23 @@
> +// PR c++/106259
> +// { dg-do compile }
> +// { dg-options "-Wmismatched-tags" }
> +
> +template<typename T> struct A {
> + template<typename U>
> + struct W { };
> +};
> +
> +template<>
> +struct A<char> {
> + template<typename U>
> + class W { };
> +};
> +
> +void
> +g ()
> +{
> + struct A<char>::W<int> w1; // { dg-warning "mismatched" }
> + struct A<int>::W<int> w2;
> + class A<char>::W<int> w3;
> + class A<int>::W<int> w4; // { dg-warning "mismatched" }
> +}
>
> base-commit: 096f034a8f5df41f610e62c1592fb90a3f551cd5
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
2023-03-01 21:30 ` Jason Merrill
@ 2023-03-01 21:40 ` Marek Polacek
2023-03-01 21:44 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Marek Polacek @ 2023-03-01 21:40 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
On Wed, Mar 01, 2023 at 04:30:16PM -0500, Jason Merrill wrote:
> On 3/1/23 15:33, Marek Polacek wrote:
> > -Wmismatched-tags warns about the (harmless) struct/class mismatch.
> > For, e.g.,
> >
> > template<typename T> struct A { };
> > class A<int> a;
> >
> > it works by adding A<T> to the class2loc hash table while parsing the
> > class-head and then, while parsing the elaborate type-specifier, we
> > add A<int>. At the end of c_parse_file we go through the table and
> > warn about the class-key mismatches. In this PR we crash though; we
> > have
> >
> > template<typename T> struct A {
> > template<typename U> struct W { };
> > };
> > struct A<int>::W<int> w; // #1
> >
> > where while parsing A and #1 we've stashed
> > A<T>
> > A<T>::W<U>
> > A<int>::W<int>
> > into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
> > is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
> > is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
> > OK not to have found A<int>::W<U>, we should just look one "level" up,
> > that is, A<T>::W<U>.
> >
> > It's important to handle class specializations, so e.g.
> >
> > template<>
> > struct A<char> {
> > template<typename U>
> > class W { };
> > };
> >
> > where W's class-key is different than in the primary template above,
> > so we should warn depending on whether we're looking into A<char>
> > or into a different instantiation.
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> >
> > PR c++/106259
> >
> > gcc/cp/ChangeLog:
> >
> > * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
> > lookup of SPEC didn't find anything, try to look for
> > most_general_template.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/warn/Wmismatched-tags-11.C: New test.
> > ---
> > gcc/cp/parser.cc | 30 +++++++++++++++----
> > .../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
> > 2 files changed, 47 insertions(+), 6 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
> >
> > diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> > index 1a124f5395e..b528ee7b1d9 100644
> > --- a/gcc/cp/parser.cc
> > +++ b/gcc/cp/parser.cc
> > @@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
> > be (and inevitably is) at index zero. */
> > tree spec = specialization_of (type);
> > cdlguide = class2loc.get (spec);
> > + /* It's possible that we didn't find SPEC. Consider:
> > +
> > + template<typename T> struct A {
> > + template<typename U> struct W { };
> > + };
> > + struct A<int>::W<int> w; // #1
> > +
> > + where while parsing A and #1 we've stashed
> > + A<T>
> > + A<T>::W<U>
> > + A<int>::W<int>
> > + into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
> > + will yield A<int>::W<U> which may be in CLASS2LOC if we had
> > + an A<int> class specialization, but otherwise won't be in it.
> > + So try to look up A<T>::W<U>. */
> > + if (!cdlguide)
> > + {
> > + spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
>
> Would it make sense to only look at most_general_template, not A<int>::W<U>
> at all?
I think that would break with class specialization, as in...
> > +template<typename T> struct A {
> > + template<typename U>
> > + struct W { };
> > +};
> > +
> > +template<>
> > +struct A<char> {
> > + template<typename U>
> > + class W { };
> > +};
> > +
> > +void
> > +g ()
> > +{
> > + struct A<char>::W<int> w1; // { dg-warning "mismatched" }
...this, where we should first look into A<char>, and only if not
found, go to A<T>.
class2loc will be filled with A<char>::W<U>, added while parsing
the specialization.
> > + struct A<int>::W<int> w2;
> > + class A<char>::W<int> w3;
> > + class A<int>::W<int> w4; // { dg-warning "mismatched" }
> > +}
> >
> > base-commit: 096f034a8f5df41f610e62c1592fb90a3f551cd5
>
Marek
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
2023-03-01 21:40 ` Marek Polacek
@ 2023-03-01 21:44 ` Jason Merrill
2023-03-01 22:33 ` Marek Polacek
0 siblings, 1 reply; 6+ messages in thread
From: Jason Merrill @ 2023-03-01 21:44 UTC (permalink / raw)
To: Marek Polacek; +Cc: GCC Patches
On 3/1/23 16:40, Marek Polacek wrote:
> On Wed, Mar 01, 2023 at 04:30:16PM -0500, Jason Merrill wrote:
>> On 3/1/23 15:33, Marek Polacek wrote:
>>> -Wmismatched-tags warns about the (harmless) struct/class mismatch.
>>> For, e.g.,
>>>
>>> template<typename T> struct A { };
>>> class A<int> a;
>>>
>>> it works by adding A<T> to the class2loc hash table while parsing the
>>> class-head and then, while parsing the elaborate type-specifier, we
>>> add A<int>. At the end of c_parse_file we go through the table and
>>> warn about the class-key mismatches. In this PR we crash though; we
>>> have
>>>
>>> template<typename T> struct A {
>>> template<typename U> struct W { };
>>> };
>>> struct A<int>::W<int> w; // #1
>>>
>>> where while parsing A and #1 we've stashed
>>> A<T>
>>> A<T>::W<U>
>>> A<int>::W<int>
>>> into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
>>> is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
>>> is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
>>> OK not to have found A<int>::W<U>, we should just look one "level" up,
>>> that is, A<T>::W<U>.
>>>
>>> It's important to handle class specializations, so e.g.
>>>
>>> template<>
>>> struct A<char> {
>>> template<typename U>
>>> class W { };
>>> };
>>>
>>> where W's class-key is different than in the primary template above,
>>> so we should warn depending on whether we're looking into A<char>
>>> or into a different instantiation.
>>>
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>
>>> PR c++/106259
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
>>> lookup of SPEC didn't find anything, try to look for
>>> most_general_template.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * g++.dg/warn/Wmismatched-tags-11.C: New test.
>>> ---
>>> gcc/cp/parser.cc | 30 +++++++++++++++----
>>> .../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
>>> 2 files changed, 47 insertions(+), 6 deletions(-)
>>> create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
>>>
>>> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
>>> index 1a124f5395e..b528ee7b1d9 100644
>>> --- a/gcc/cp/parser.cc
>>> +++ b/gcc/cp/parser.cc
>>> @@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
>>> be (and inevitably is) at index zero. */
>>> tree spec = specialization_of (type);
>>> cdlguide = class2loc.get (spec);
>>> + /* It's possible that we didn't find SPEC. Consider:
>>> +
>>> + template<typename T> struct A {
>>> + template<typename U> struct W { };
>>> + };
>>> + struct A<int>::W<int> w; // #1
>>> +
>>> + where while parsing A and #1 we've stashed
>>> + A<T>
>>> + A<T>::W<U>
>>> + A<int>::W<int>
>>> + into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
>>> + will yield A<int>::W<U> which may be in CLASS2LOC if we had
>>> + an A<int> class specialization, but otherwise won't be in it.
>>> + So try to look up A<T>::W<U>. */
>>> + if (!cdlguide)
>>> + {
>>> + spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
>>
>> Would it make sense to only look at most_general_template, not A<int>::W<U>
>> at all?
>
> I think that would break with class specialization, as in...
>
>>> +template<typename T> struct A {
>>> + template<typename U>
>>> + struct W { };
>>> +};
>>> +
>>> +template<>
>>> +struct A<char> {
>>> + template<typename U>
>>> + class W { };
>>> +};
>>> +
>>> +void
>>> +g ()
>>> +{
>>> + struct A<char>::W<int> w1; // { dg-warning "mismatched" }
>
> ...this, where we should first look into A<char>, and only if not
> found, go to A<T>.
I'd expect the
> /* Stop if we run into an explicitly specialized class template. */
code in most_general_template to avoid that problem.
Jason
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
2023-03-01 21:44 ` Jason Merrill
@ 2023-03-01 22:33 ` Marek Polacek
2023-03-02 15:43 ` Jason Merrill
0 siblings, 1 reply; 6+ messages in thread
From: Marek Polacek @ 2023-03-01 22:33 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
On Wed, Mar 01, 2023 at 04:44:12PM -0500, Jason Merrill wrote:
> On 3/1/23 16:40, Marek Polacek wrote:
> > On Wed, Mar 01, 2023 at 04:30:16PM -0500, Jason Merrill wrote:
> > > On 3/1/23 15:33, Marek Polacek wrote:
> > > > -Wmismatched-tags warns about the (harmless) struct/class mismatch.
> > > > For, e.g.,
> > > >
> > > > template<typename T> struct A { };
> > > > class A<int> a;
> > > >
> > > > it works by adding A<T> to the class2loc hash table while parsing the
> > > > class-head and then, while parsing the elaborate type-specifier, we
> > > > add A<int>. At the end of c_parse_file we go through the table and
> > > > warn about the class-key mismatches. In this PR we crash though; we
> > > > have
> > > >
> > > > template<typename T> struct A {
> > > > template<typename U> struct W { };
> > > > };
> > > > struct A<int>::W<int> w; // #1
> > > >
> > > > where while parsing A and #1 we've stashed
> > > > A<T>
> > > > A<T>::W<U>
> > > > A<int>::W<int>
> > > > into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
> > > > is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
> > > > is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
> > > > OK not to have found A<int>::W<U>, we should just look one "level" up,
> > > > that is, A<T>::W<U>.
> > > >
> > > > It's important to handle class specializations, so e.g.
> > > >
> > > > template<>
> > > > struct A<char> {
> > > > template<typename U>
> > > > class W { };
> > > > };
> > > >
> > > > where W's class-key is different than in the primary template above,
> > > > so we should warn depending on whether we're looking into A<char>
> > > > or into a different instantiation.
> > > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > >
> > > > PR c++/106259
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
> > > > lookup of SPEC didn't find anything, try to look for
> > > > most_general_template.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > * g++.dg/warn/Wmismatched-tags-11.C: New test.
> > > > ---
> > > > gcc/cp/parser.cc | 30 +++++++++++++++----
> > > > .../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
> > > > 2 files changed, 47 insertions(+), 6 deletions(-)
> > > > create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
> > > >
> > > > diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> > > > index 1a124f5395e..b528ee7b1d9 100644
> > > > --- a/gcc/cp/parser.cc
> > > > +++ b/gcc/cp/parser.cc
> > > > @@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
> > > > be (and inevitably is) at index zero. */
> > > > tree spec = specialization_of (type);
> > > > cdlguide = class2loc.get (spec);
> > > > + /* It's possible that we didn't find SPEC. Consider:
> > > > +
> > > > + template<typename T> struct A {
> > > > + template<typename U> struct W { };
> > > > + };
> > > > + struct A<int>::W<int> w; // #1
> > > > +
> > > > + where while parsing A and #1 we've stashed
> > > > + A<T>
> > > > + A<T>::W<U>
> > > > + A<int>::W<int>
> > > > + into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
> > > > + will yield A<int>::W<U> which may be in CLASS2LOC if we had
> > > > + an A<int> class specialization, but otherwise won't be in it.
> > > > + So try to look up A<T>::W<U>. */
> > > > + if (!cdlguide)
> > > > + {
> > > > + spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
> > >
> > > Would it make sense to only look at most_general_template, not A<int>::W<U>
> > > at all?
> >
> > I think that would break with class specialization, as in...
> >
> > > > +template<typename T> struct A {
> > > > + template<typename U>
> > > > + struct W { };
> > > > +};
> > > > +
> > > > +template<>
> > > > +struct A<char> {
> > > > + template<typename U>
> > > > + class W { };
> > > > +};
> > > > +
> > > > +void
> > > > +g ()
> > > > +{
> > > > + struct A<char>::W<int> w1; // { dg-warning "mismatched" }
> >
> > ...this, where we should first look into A<char>, and only if not
> > found, go to A<T>.
>
> I'd expect the
>
> > /* Stop if we run into an explicitly specialized class template. */
>
> code in most_general_template to avoid that problem.
Ah, I had no idea it does that. The unconditional most_general_template
works fine for the new test, but some of the existing tests then fail.
Reduced:
template <class Z> struct S2; // #1
template <class T> class S2<const T>; // #2
extern class S2<const int> s2ci; // #3
extern struct S2<const int> s2ci; // { dg-warning "\\\[-Wmismatched-tags" }
where the unconditional most_general_template changes spec from
"class S2<const T>" to "struct S2<Z>" (both of which are in class2loc).
So it regresses the diagnostic, complaining that #3 should have "struct"
since #1 has "struct". I think we want to keep the current diagnostic,
saying that the last line should have "class" since the specialization
in line #2 has "class".
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259]
2023-03-01 22:33 ` Marek Polacek
@ 2023-03-02 15:43 ` Jason Merrill
0 siblings, 0 replies; 6+ messages in thread
From: Jason Merrill @ 2023-03-02 15:43 UTC (permalink / raw)
To: Marek Polacek; +Cc: GCC Patches
On 3/1/23 17:33, Marek Polacek wrote:
> On Wed, Mar 01, 2023 at 04:44:12PM -0500, Jason Merrill wrote:
>> On 3/1/23 16:40, Marek Polacek wrote:
>>> On Wed, Mar 01, 2023 at 04:30:16PM -0500, Jason Merrill wrote:
>>>> On 3/1/23 15:33, Marek Polacek wrote:
>>>>> -Wmismatched-tags warns about the (harmless) struct/class mismatch.
>>>>> For, e.g.,
>>>>>
>>>>> template<typename T> struct A { };
>>>>> class A<int> a;
>>>>>
>>>>> it works by adding A<T> to the class2loc hash table while parsing the
>>>>> class-head and then, while parsing the elaborate type-specifier, we
>>>>> add A<int>. At the end of c_parse_file we go through the table and
>>>>> warn about the class-key mismatches. In this PR we crash though; we
>>>>> have
>>>>>
>>>>> template<typename T> struct A {
>>>>> template<typename U> struct W { };
>>>>> };
>>>>> struct A<int>::W<int> w; // #1
>>>>>
>>>>> where while parsing A and #1 we've stashed
>>>>> A<T>
>>>>> A<T>::W<U>
>>>>> A<int>::W<int>
>>>>> into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE
>>>>> is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which
>>>>> is not in class2loc, so we crash on gcc_assert (cdlguide). But it's
>>>>> OK not to have found A<int>::W<U>, we should just look one "level" up,
>>>>> that is, A<T>::W<U>.
>>>>>
>>>>> It's important to handle class specializations, so e.g.
>>>>>
>>>>> template<>
>>>>> struct A<char> {
>>>>> template<typename U>
>>>>> class W { };
>>>>> };
>>>>>
>>>>> where W's class-key is different than in the primary template above,
>>>>> so we should warn depending on whether we're looking into A<char>
>>>>> or into a different instantiation.
>>>>>
>>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>>>
>>>>> PR c++/106259
>>>>>
>>>>> gcc/cp/ChangeLog:
>>>>>
>>>>> * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first
>>>>> lookup of SPEC didn't find anything, try to look for
>>>>> most_general_template.
>>>>>
>>>>> gcc/testsuite/ChangeLog:
>>>>>
>>>>> * g++.dg/warn/Wmismatched-tags-11.C: New test.
>>>>> ---
>>>>> gcc/cp/parser.cc | 30 +++++++++++++++----
>>>>> .../g++.dg/warn/Wmismatched-tags-11.C | 23 ++++++++++++++
>>>>> 2 files changed, 47 insertions(+), 6 deletions(-)
>>>>> create mode 100644 gcc/testsuite/g++.dg/warn/Wmismatched-tags-11.C
>>>>>
>>>>> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
>>>>> index 1a124f5395e..b528ee7b1d9 100644
>>>>> --- a/gcc/cp/parser.cc
>>>>> +++ b/gcc/cp/parser.cc
>>>>> @@ -34473,14 +34473,32 @@ class_decl_loc_t::diag_mismatched_tags (tree type_decl)
>>>>> be (and inevitably is) at index zero. */
>>>>> tree spec = specialization_of (type);
>>>>> cdlguide = class2loc.get (spec);
>>>>> + /* It's possible that we didn't find SPEC. Consider:
>>>>> +
>>>>> + template<typename T> struct A {
>>>>> + template<typename U> struct W { };
>>>>> + };
>>>>> + struct A<int>::W<int> w; // #1
>>>>> +
>>>>> + where while parsing A and #1 we've stashed
>>>>> + A<T>
>>>>> + A<T>::W<U>
>>>>> + A<int>::W<int>
>>>>> + into CLASS2LOC. If TYPE is A<int>::W<int>, specialization_of
>>>>> + will yield A<int>::W<U> which may be in CLASS2LOC if we had
>>>>> + an A<int> class specialization, but otherwise won't be in it.
>>>>> + So try to look up A<T>::W<U>. */
>>>>> + if (!cdlguide)
>>>>> + {
>>>>> + spec = DECL_TEMPLATE_RESULT (most_general_template (spec));
>>>>
>>>> Would it make sense to only look at most_general_template, not A<int>::W<U>
>>>> at all?
>>>
>>> I think that would break with class specialization, as in...
>>>
>>>>> +template<typename T> struct A {
>>>>> + template<typename U>
>>>>> + struct W { };
>>>>> +};
>>>>> +
>>>>> +template<>
>>>>> +struct A<char> {
>>>>> + template<typename U>
>>>>> + class W { };
>>>>> +};
>>>>> +
>>>>> +void
>>>>> +g ()
>>>>> +{
>>>>> + struct A<char>::W<int> w1; // { dg-warning "mismatched" }
>>>
>>> ...this, where we should first look into A<char>, and only if not
>>> found, go to A<T>.
>>
>> I'd expect the
>>
>>> /* Stop if we run into an explicitly specialized class template. */
>>
>> code in most_general_template to avoid that problem.
>
> Ah, I had no idea it does that. The unconditional most_general_template
> works fine for the new test, but some of the existing tests then fail.
> Reduced:
>
> template <class Z> struct S2; // #1
> template <class T> class S2<const T>; // #2
>
> extern class S2<const int> s2ci; // #3
> extern struct S2<const int> s2ci; // { dg-warning "\\\[-Wmismatched-tags" }
>
> where the unconditional most_general_template changes spec from
> "class S2<const T>" to "struct S2<Z>" (both of which are in class2loc).
> So it regresses the diagnostic, complaining that #3 should have "struct"
> since #1 has "struct". I think we want to keep the current diagnostic,
> saying that the last line should have "class" since the specialization
> in line #2 has "class".
Makes sense, the patch is OK.
Jason
^ permalink raw reply [flat|nested] 6+ messages in thread
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2023-03-01 20:33 [PATCH] c++: ICE with -Wmismatched-tags and member template [PR106259] Marek Polacek
2023-03-01 21:30 ` Jason Merrill
2023-03-01 21:40 ` Marek Polacek
2023-03-01 21:44 ` Jason Merrill
2023-03-01 22:33 ` Marek Polacek
2023-03-02 15:43 ` Jason Merrill
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