From 71afd0628419c5d670701cb35bc9860380c7d9fb Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Wed, 1 Mar 2023 14:28:46 -0500
Subject: [PATCH] c++: ICE with -Wmismatched-tags and member template
[PR106259]
-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.
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 3d6b8f252a35..b00a6cd5b8b3 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 000000000000..6c4e571726aa
--- /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" }
+}
--
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