On Fri, Jan 21, 2022 at 09:27:17AM -0500, Jason Merrill wrote:
> On 1/20/22 20:03, Marek Polacek wrote:
> > @@ -2815,12 +2816,23 @@ fixup_deferred_exception_variants (tree type, tree
> > raises)
> > cp_cv_quals var_quals = TYPE_QUALS (variant);
> > cp_ref_qualifier rqual = type_memfn_rqual (variant);
> > + /* If VARIANT would become a dup (cp_check_qualified_type-wise)
> > + of an existing variant in the variant list of TYPE after its
> > + exception specification has been parsed, elide it. Otherwise,
> > + build_cp_fntype_variant could use it, leading to "canonical
> > + types differ for identical types." */
> > tree v = TYPE_MAIN_VARIANT (type);
> > for (; v; v = TYPE_NEXT_VARIANT (v))
> > if (TYPE_CANONICAL (v) == v
>
> I think we want to drop the TYPE_CANONICAL check here, and below change
>
> TYPE_CANONICAL (variant) = v;
>
> to
>
> TYPE_CANONICAL (variant) = TYPE_CANONICAL (v);
OK. I couldn't really find a way to test it; clang++ rejected
my attempts with "error: exception specifications are not allowed in
typedefs" so I'm not sure if I want to add such tests even though we
happen to accept it currently.
> so that this also works for e.g. signatures involving typedefs.
>
> > + && v != variant
>
> I think we don't need this check since we haven't changed
> TYPE_RAISES_EXCEPTIONS yet.
And variant will never be the main variant, because of the
if (TYPE_RAISES_EXCEPTIONS (variant) == original)
check. Ok, so the following should be enough:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
This is a "canonical types differ for identical types" ICE, which started
with r11-4682. It's a bit tricky to explain. Consider:
template <typename T> struct S {
S<T> bar() noexcept(T::value); // #1
S<T> foo() noexcept(T::value); // #2
};
template <typename T> S<T> S<T>::foo() noexcept(T::value) {} // #3
We ICE because #3 and #2 have the same type, but their canonical types
differ: TYPE_CANONICAL (#3) == #2 but TYPE_CANONICAL (#2) == #1.
The member functions #1 and #2 have the same type. However, since their
noexcept-specifier is deferred, when parsing them, we create a variant for
both of them, because DEFERRED_PARSE cannot be compared. In other words,
build_cp_fntype_variant's
tree v = TYPE_MAIN_VARIANT (type);
for (; v; v = TYPE_NEXT_VARIANT (v))
if (cp_check_qualified_type (v, type, type_quals, rqual, raises, late))
return v;
will *not* find an existing variant when creating a method_type for #2, so we
have to create a new one.
But then we perform delayed parsing and call fixup_deferred_exception_variants
for #1 and #2. f_d_e_v will replace TYPE_RAISES_EXCEPTIONS with the newly
parsed noexcept-specifier. It also sets TYPE_CANONICAL (#2) to #1. Both
noexcepts turned out to be the same, so now we have two equivalent variants in
the list! I.e.,
+-----------------+ +-----------------+ +-----------------+
| main | | #2 | | #1 |
| S S::<T379>(S*) |----->| S S::<T37c>(S*) |----->| S S::<T37a>(S*) |----->NULL
| - | | noex(T::value) | | noex(T::value) |
+-----------------+ +-----------------+ +-----------------+
Then we get to #3. As for #1 and #2, grokdeclarator calls build_memfn_type,
which ends up calling build_cp_fntype_variant, which will use the loop
above to look for an existing variant. The first one that matches
cp_check_qualified_type will be used, so we use #2 rather than #1, and the
TYPE_CANONICAL mismatch follows. Hopefully that makes sense.
As for the fix, I didn't think I could rewrite the method_type #2 with #1
because the type may have escaped via decltype. So my approach is to
elide #2 from the list, so when looking for a matching variant, we always
find #1 (#2 remains live though, which admittedly sounds sort of dodgy).
PR c++/101715
gcc/cp/ChangeLog:
* tree.c (fixup_deferred_exception_variants): Remove duplicate
variants after parsing the exception specifications.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept72.C: New test.
* g++.dg/cpp0x/noexcept73.C: New test.
---
gcc/cp/tree.cc | 22 ++++++++++++++++------
gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
3 files changed, 50 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept72.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept73.C
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index bcd44e73921..f88006aec4f 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -2804,8 +2804,9 @@ fixup_deferred_exception_variants (tree type, tree raises)
/* Though sucky, this walk will process the canonical variants
first. */
+ tree prev = NULL_TREE;
for (tree variant = TYPE_MAIN_VARIANT (type);
- variant; variant = TYPE_NEXT_VARIANT (variant))
+ variant; prev = variant, variant = TYPE_NEXT_VARIANT (variant))
if (TYPE_RAISES_EXCEPTIONS (variant) == original)
{
gcc_checking_assert (variant != TYPE_MAIN_VARIANT (type));
@@ -2815,18 +2816,27 @@ fixup_deferred_exception_variants (tree type, tree
raises)
cp_cv_quals var_quals = TYPE_QUALS (variant);
cp_ref_qualifier rqual = type_memfn_rqual (variant);
+ /* If VARIANT would become a dup (cp_check_qualified_type-wise)
+ of an existing variant in the variant list of TYPE after its
+ exception specification has been parsed, elide it. Otherwise,
+ build_cp_fntype_variant could use it, leading to "canonical
+ types differ for identical types." */
tree v = TYPE_MAIN_VARIANT (type);
for (; v; v = TYPE_NEXT_VARIANT (v))
- if (TYPE_CANONICAL (v) == v
- && cp_check_qualified_type (v, variant, var_quals,
- rqual, cr, false))
- break;
+ if (cp_check_qualified_type (v, variant, var_quals,
+ rqual, cr, false))
+ {
+ /* The main variant will not match V, so PREV will never
+ be null. */
+ TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
+ break;
+ }
TYPE_RAISES_EXCEPTIONS (variant) = raises;
if (!v)
v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
rqual, cr, false);
- TYPE_CANONICAL (variant) = v;
+ TYPE_CANONICAL (variant) = TYPE_CANONICAL (v);
}
else
TYPE_RAISES_EXCEPTIONS (variant) = raises;
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept72.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept72.C
new file mode 100644
index 00000000000..f1455b3b46b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept72.C
@@ -0,0 +1,21 @@
+// PR c++/101715
+// { dg-do compile { target c++11 } }
+
+template <typename T> struct S {
+ S<T> bar() noexcept(T::value); // #1
+ S<T> foo() noexcept(T::value); // #2
+};
+
+template <typename T> S<T> S<T>::foo() noexcept(T::value) {} // #3
+
+template <typename T> struct S2 {
+ S2<T> bar1() noexcept(T::value);
+ S2<T> bar2() noexcept(T::value);
+ S2<T> bar3() noexcept(T::value);
+ S2<T> bar4() noexcept(T::value);
+ S2<T> bar5() noexcept(T::value);
+ S2<T> baz() noexcept(T::value2);
+ S2<T> foo() noexcept(T::value);
+};
+
+template <typename T> S2<T> S2<T>::foo() noexcept(T::value) {}
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept73.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept73.C
new file mode 100644
index 00000000000..24524f3592a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept73.C
@@ -0,0 +1,13 @@
+// PR c++/101715
+// { dg-do compile { target c++11 } }
+
+template <typename T> struct S { };
+
+template<typename T>
+struct A
+{
+ A& foo(A&&) noexcept((S<T>::value));
+ A& assign(A&&) noexcept((S<T>::value));
+};
+template<typename T>
+A<T>& A<T>::foo(A&&) noexcept((S<T>::value)) {}
base-commit: 45cae5b6392496028f35c5948f7fae0af81d135b
--
2.34.1
