* [PATCH] c++: ICE with noexcept and canonical types [PR101715]
@ 2022-01-15 0:22 Marek Polacek
2022-01-15 14:24 ` Patrick Palka
2022-01-17 18:48 ` Jason Merrill
0 siblings, 2 replies; 10+ messages in thread
From: Marek Polacek @ 2022-01-15 0:22 UTC (permalink / raw)
To: Jason Merrill, Nathan Sidwell, GCC Patches
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).
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
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.c | 16 +++++++++++++++-
gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
3 files changed, 49 insertions(+), 1 deletion(-)
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.c b/gcc/cp/tree.c
index 7f7de86b4e8..2efad49e7c1 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -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));
@@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
rqual, cr, false);
TYPE_CANONICAL (variant) = v;
+
+ /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
+ of an existing variant in the variant list of TYPE after we
+ have parsed its exception specification, elide it. Otherwise,
+ build_cp_fntype_variant would use it, leading to "canonical
+ types differ for identical types." */
+ for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
+ if (v != variant
+ /* The main variant will not have TYPE_RAISES_EXCEPTIONS
+ so PREV should never be null. */
+ && cp_check_qualified_type (v, variant, var_quals,
+ rqual, cr, false))
+ TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
}
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: 952b7dbb418198f86d7829aaf9d7f9fc7714a8b3
--
2.34.1
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715]
2022-01-15 0:22 [PATCH] c++: ICE with noexcept and canonical types [PR101715] Marek Polacek
@ 2022-01-15 14:24 ` Patrick Palka
2022-01-18 16:08 ` Marek Polacek
2022-01-17 18:48 ` Jason Merrill
1 sibling, 1 reply; 10+ messages in thread
From: Patrick Palka @ 2022-01-15 14:24 UTC (permalink / raw)
To: Marek Polacek; +Cc: Jason Merrill, Nathan Sidwell, GCC Patches
On Fri, 14 Jan 2022, Marek Polacek via Gcc-patches wrote:
> 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).
I wonder about instead making build_cp_fntype_variant set the TYPE_CANONICAL for
#3 to TYPE_CANONICAL(#2) (i.e. #1) instead of to #2? Something like:
-- >8 --
gcc/cp/tree.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 7f7de86b4e8..b89135fa121 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -2779,8 +2779,9 @@ build_cp_fntype_variant (tree type, cp_ref_qualifier rqual,
else if (TYPE_CANONICAL (type) != type || cr != raises || late)
/* Build the underlying canonical type, since it is different
from TYPE. */
- TYPE_CANONICAL (v) = build_cp_fntype_variant (TYPE_CANONICAL (type),
- rqual, cr, false);
+ TYPE_CANONICAL (v)
+ = TYPE_CANONICAL (build_cp_fntype_variant (TYPE_CANONICAL (type),
+ rqual, cr, false));
else
/* T is its own canonical type. */
TYPE_CANONICAL (v) = v;
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715]
2022-01-15 0:22 [PATCH] c++: ICE with noexcept and canonical types [PR101715] Marek Polacek
2022-01-15 14:24 ` Patrick Palka
@ 2022-01-17 18:48 ` Jason Merrill
2022-01-18 16:05 ` Marek Polacek
1 sibling, 1 reply; 10+ messages in thread
From: Jason Merrill @ 2022-01-17 18:48 UTC (permalink / raw)
To: Marek Polacek, Nathan Sidwell, GCC Patches
On 1/14/22 19:22, Marek Polacek wrote:
> 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.
Why doesn't the TYPE_CANONICAL (v) == v check prevent this?
> 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).
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
>
> 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.c | 16 +++++++++++++++-
> gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
> gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
> 3 files changed, 49 insertions(+), 1 deletion(-)
> 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.c b/gcc/cp/tree.c
> index 7f7de86b4e8..2efad49e7c1 100644
> --- a/gcc/cp/tree.c
> +++ b/gcc/cp/tree.c
> @@ -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));
> @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
> v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
> rqual, cr, false);
> TYPE_CANONICAL (variant) = v;
> +
> + /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
> + of an existing variant in the variant list of TYPE after we
> + have parsed its exception specification, elide it. Otherwise,
> + build_cp_fntype_variant would use it, leading to "canonical
> + types differ for identical types." */
> + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
> + if (v != variant
> + /* The main variant will not have TYPE_RAISES_EXCEPTIONS
> + so PREV should never be null. */
> + && cp_check_qualified_type (v, variant, var_quals,
> + rqual, cr, false))
> + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
> }
> 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: 952b7dbb418198f86d7829aaf9d7f9fc7714a8b3
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715]
2022-01-17 18:48 ` Jason Merrill
@ 2022-01-18 16:05 ` Marek Polacek
2022-01-20 20:23 ` Jason Merrill
0 siblings, 1 reply; 10+ messages in thread
From: Marek Polacek @ 2022-01-18 16:05 UTC (permalink / raw)
To: Jason Merrill; +Cc: Nathan Sidwell, GCC Patches
On Mon, Jan 17, 2022 at 01:48:48PM -0500, Jason Merrill wrote:
> On 1/14/22 19:22, Marek Polacek wrote:
> > 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.
>
> Why doesn't the TYPE_CANONICAL (v) == v check prevent this?
In other words, I think you're asking: why did fixup_deferred_exception_variants
set TYPE_CANONICAL (#2) to #1 (which then differs from TYPE_CANONICAL (#3),
which is #2)?
The method_type for #1 (I'll mark is as #1 here) is built with it being its own
canonical type.
The first call to fixup_deferred_exception_variants does not change it: in
there, VARIANT is #1, the loop with 'TYPE_CANONICAL (v) == v' cannot find
an existing variant that would match, so when we do
v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
rqual, cr, false);
we get #1 so
TYPE_CANONICAL (variant) = v;
is just
TYPE_CANONICAL (#1) = #1;
so no change.
The second call to fixup_deferred_exception_variants: here we're working with
VARIANT #2. Now we again scan the list of variants {main, #2, #1} where we
find a match for #2: #1. #1's TYPE_CANONICAL is #1 as per above, so we set
TYPE_CANONICAL (#2) = #1;
which I think is correct.
I think TYPE_CANONICAL (#3) should also be #1, not #2, which my patch attempts
to do.
Hope this explanation makes some sense, please ask away if it doesn't!
> > 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).
> >
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
> >
> > 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.c | 16 +++++++++++++++-
> > gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
> > gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
> > 3 files changed, 49 insertions(+), 1 deletion(-)
> > 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.c b/gcc/cp/tree.c
> > index 7f7de86b4e8..2efad49e7c1 100644
> > --- a/gcc/cp/tree.c
> > +++ b/gcc/cp/tree.c
> > @@ -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));
> > @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
> > v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
> > rqual, cr, false);
> > TYPE_CANONICAL (variant) = v;
> > +
> > + /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
> > + of an existing variant in the variant list of TYPE after we
> > + have parsed its exception specification, elide it. Otherwise,
> > + build_cp_fntype_variant would use it, leading to "canonical
> > + types differ for identical types." */
> > + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
> > + if (v != variant
> > + /* The main variant will not have TYPE_RAISES_EXCEPTIONS
> > + so PREV should never be null. */
> > + && cp_check_qualified_type (v, variant, var_quals,
> > + rqual, cr, false))
> > + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
> > }
> > 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: 952b7dbb418198f86d7829aaf9d7f9fc7714a8b3
>
Marek
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715]
2022-01-15 14:24 ` Patrick Palka
@ 2022-01-18 16:08 ` Marek Polacek
0 siblings, 0 replies; 10+ messages in thread
From: Marek Polacek @ 2022-01-18 16:08 UTC (permalink / raw)
To: Patrick Palka; +Cc: Jason Merrill, Nathan Sidwell, GCC Patches
On Sat, Jan 15, 2022 at 09:24:05AM -0500, Patrick Palka wrote:
> On Fri, 14 Jan 2022, Marek Polacek via Gcc-patches wrote:
>
> > 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).
>
> I wonder about instead making build_cp_fntype_variant set the TYPE_CANONICAL for
> #3 to TYPE_CANONICAL(#2) (i.e. #1) instead of to #2? Something like:
>
> -- >8 --
>
> gcc/cp/tree.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
> index 7f7de86b4e8..b89135fa121 100644
> --- a/gcc/cp/tree.c
> +++ b/gcc/cp/tree.c
> @@ -2779,8 +2779,9 @@ build_cp_fntype_variant (tree type, cp_ref_qualifier rqual,
> else if (TYPE_CANONICAL (type) != type || cr != raises || late)
> /* Build the underlying canonical type, since it is different
> from TYPE. */
> - TYPE_CANONICAL (v) = build_cp_fntype_variant (TYPE_CANONICAL (type),
> - rqual, cr, false);
> + TYPE_CANONICAL (v)
> + = TYPE_CANONICAL (build_cp_fntype_variant (TYPE_CANONICAL (type),
> + rqual, cr, false));
> else
> /* T is its own canonical type. */
> TYPE_CANONICAL (v) = v;
Thanks for looking. I can dig that (and verified it works), but it strikes
me more as a workaround for the duplicity problem. I also don't see
TYPE_CANONICAL (...) = TYPE_CANONICAL (build_cp_fntype_variant (...))
anywhere in the codebase, if that means anything.
Marek
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715]
2022-01-18 16:05 ` Marek Polacek
@ 2022-01-20 20:23 ` Jason Merrill
2022-01-21 1:03 ` [PATCH v2] " Marek Polacek
0 siblings, 1 reply; 10+ messages in thread
From: Jason Merrill @ 2022-01-20 20:23 UTC (permalink / raw)
To: Marek Polacek; +Cc: Nathan Sidwell, GCC Patches
On 1/18/22 11:05, Marek Polacek wrote:
> On Mon, Jan 17, 2022 at 01:48:48PM -0500, Jason Merrill wrote:
>> On 1/14/22 19:22, Marek Polacek wrote:
>>> 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.
>>
>> Why doesn't the TYPE_CANONICAL (v) == v check prevent this?
>
> In other words, I think you're asking: why did fixup_deferred_exception_variants
> set TYPE_CANONICAL (#2) to #1 (which then differs from TYPE_CANONICAL (#3),
> which is #2)?
I meant to ask why TYPE_CANONICAL (#3) got set to #2 instead of #1?
And to answer my own question, it's because the check I mention is in
fixup_deferred_exception_variants, and #3 doesn't go through there at
all; the loop in build_cp_fntype_variant assumes no duplicate variants,
which your patch fixes.
> The method_type for #1 (I'll mark is as #1 here) is built with it being its own
> canonical type.
>
> The first call to fixup_deferred_exception_variants does not change it: in
> there, VARIANT is #1, the loop with 'TYPE_CANONICAL (v) == v' cannot find
> an existing variant that would match, so when we do
>
> v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
> rqual, cr, false);
> we get #1 so
> TYPE_CANONICAL (variant) = v;
> is just
> TYPE_CANONICAL (#1) = #1;
> so no change.
>
> The second call to fixup_deferred_exception_variants: here we're working with
> VARIANT #2. Now we again scan the list of variants {main, #2, #1} where we
> find a match for #2: #1. #1's TYPE_CANONICAL is #1 as per above, so we set
> TYPE_CANONICAL (#2) = #1;
> which I think is correct.
>
>
> I think TYPE_CANONICAL (#3) should also be #1, not #2, which my patch attempts
> to do.
>
>
> Hope this explanation makes some sense, please ask away if it doesn't!
>
>>> 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).
>>>
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
>>>
>>> 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.c | 16 +++++++++++++++-
>>> gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
>>> gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
>>> 3 files changed, 49 insertions(+), 1 deletion(-)
>>> 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.c b/gcc/cp/tree.c
>>> index 7f7de86b4e8..2efad49e7c1 100644
>>> --- a/gcc/cp/tree.c
>>> +++ b/gcc/cp/tree.c
>>> @@ -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));
>>> @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
>>> v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
>>> rqual, cr, false);
>>> TYPE_CANONICAL (variant) = v;
>>> +
>>> + /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
>>> + of an existing variant in the variant list of TYPE after we
>>> + have parsed its exception specification, elide it. Otherwise,
>>> + build_cp_fntype_variant would use it, leading to "canonical
>>> + types differ for identical types." */
>>> + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
>>> + if (v != variant
>>> + /* The main variant will not have TYPE_RAISES_EXCEPTIONS
>>> + so PREV should never be null. */
>>> + && cp_check_qualified_type (v, variant, var_quals,
>>> + rqual, cr, false))
>>> + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
I think we don't two loops through the variants. It ought to work to
replace the existing loop with yours; if we find v, we prune and use its
TYPE_CANONICAL.
Jason
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v2] c++: ICE with noexcept and canonical types [PR101715]
2022-01-20 20:23 ` Jason Merrill
@ 2022-01-21 1:03 ` Marek Polacek
2022-01-21 14:27 ` Jason Merrill
0 siblings, 1 reply; 10+ messages in thread
From: Marek Polacek @ 2022-01-21 1:03 UTC (permalink / raw)
To: Jason Merrill; +Cc: Nathan Sidwell, GCC Patches
On Thu, Jan 20, 2022 at 03:23:24PM -0500, Jason Merrill wrote:
> On 1/18/22 11:05, Marek Polacek wrote:
> > On Mon, Jan 17, 2022 at 01:48:48PM -0500, Jason Merrill wrote:
> > > On 1/14/22 19:22, Marek Polacek wrote:
> > > > 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.
> > >
> > > Why doesn't the TYPE_CANONICAL (v) == v check prevent this?
> >
> > In other words, I think you're asking: why did fixup_deferred_exception_variants
> > set TYPE_CANONICAL (#2) to #1 (which then differs from TYPE_CANONICAL (#3),
> > which is #2)?
>
> I meant to ask why TYPE_CANONICAL (#3) got set to #2 instead of #1?
>
> And to answer my own question, it's because the check I mention is in
> fixup_deferred_exception_variants, and #3 doesn't go through there at all;
> the loop in build_cp_fntype_variant assumes no duplicate variants, which
> your patch fixes.
Right, fixup_deferred_exception_variants is only called for fn decls in
unparsed_noexcepts.
> > The method_type for #1 (I'll mark is as #1 here) is built with it being its own
> > canonical type.
> >
> > The first call to fixup_deferred_exception_variants does not change it: in
> > there, VARIANT is #1, the loop with 'TYPE_CANONICAL (v) == v' cannot find
> > an existing variant that would match, so when we do
> >
> > v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
> > rqual, cr, false);
> > we get #1 so
> > TYPE_CANONICAL (variant) = v;
> > is just
> > TYPE_CANONICAL (#1) = #1;
> > so no change.
> >
> > The second call to fixup_deferred_exception_variants: here we're working with
> > VARIANT #2. Now we again scan the list of variants {main, #2, #1} where we
> > find a match for #2: #1. #1's TYPE_CANONICAL is #1 as per above, so we set
> > TYPE_CANONICAL (#2) = #1;
> > which I think is correct.
> >
> >
> > I think TYPE_CANONICAL (#3) should also be #1, not #2, which my patch attempts
> > to do.
> >
> >
> > Hope this explanation makes some sense, please ask away if it doesn't!
> >
> > > > 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).
> > > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
> > > >
> > > > 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.c | 16 +++++++++++++++-
> > > > gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
> > > > gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
> > > > 3 files changed, 49 insertions(+), 1 deletion(-)
> > > > 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.c b/gcc/cp/tree.c
> > > > index 7f7de86b4e8..2efad49e7c1 100644
> > > > --- a/gcc/cp/tree.c
> > > > +++ b/gcc/cp/tree.c
> > > > @@ -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));
> > > > @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
> > > > v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
> > > > rqual, cr, false);
> > > > TYPE_CANONICAL (variant) = v;
> > > > +
> > > > + /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
> > > > + of an existing variant in the variant list of TYPE after we
> > > > + have parsed its exception specification, elide it. Otherwise,
> > > > + build_cp_fntype_variant would use it, leading to "canonical
> > > > + types differ for identical types." */
> > > > + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
> > > > + if (v != variant
> > > > + /* The main variant will not have TYPE_RAISES_EXCEPTIONS
> > > > + so PREV should never be null. */
> > > > + && cp_check_qualified_type (v, variant, var_quals,
> > > > + rqual, cr, false))
> > > > + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
>
> I think we don't two loops through the variants. It ought to work to
> replace the existing loop with yours; if we find v, we prune and use its
> TYPE_CANONICAL.
Ah yes, good idea; I don't actually need to wait till TYPE_RAISES_EXCEPTIONS
is set on variant! The following seems to work just as well.
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 | 16 ++++++++++++++--
gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
3 files changed, 48 insertions(+), 2 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..17436f0512d 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));
@@ -2815,12 +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
+ && v != variant
&& cp_check_qualified_type (v, variant, var_quals,
rqual, cr, false))
- break;
+ {
+ /* 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)
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: d2ad748eeef0dd260f3993b8dcbffbded3240a0a
--
2.34.1
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] c++: ICE with noexcept and canonical types [PR101715]
2022-01-21 1:03 ` [PATCH v2] " Marek Polacek
@ 2022-01-21 14:27 ` Jason Merrill
2022-01-21 17:42 ` [PATCH v3] " Marek Polacek
0 siblings, 1 reply; 10+ messages in thread
From: Jason Merrill @ 2022-01-21 14:27 UTC (permalink / raw)
To: Marek Polacek; +Cc: Nathan Sidwell, GCC Patches
On 1/20/22 20:03, Marek Polacek wrote:
> On Thu, Jan 20, 2022 at 03:23:24PM -0500, Jason Merrill wrote:
>> On 1/18/22 11:05, Marek Polacek wrote:
>>> On Mon, Jan 17, 2022 at 01:48:48PM -0500, Jason Merrill wrote:
>>>> On 1/14/22 19:22, Marek Polacek wrote:
>>>>> 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.
>>>>
>>>> Why doesn't the TYPE_CANONICAL (v) == v check prevent this?
>>>
>>> In other words, I think you're asking: why did fixup_deferred_exception_variants
>>> set TYPE_CANONICAL (#2) to #1 (which then differs from TYPE_CANONICAL (#3),
>>> which is #2)?
>>
>> I meant to ask why TYPE_CANONICAL (#3) got set to #2 instead of #1?
>>
>> And to answer my own question, it's because the check I mention is in
>> fixup_deferred_exception_variants, and #3 doesn't go through there at all;
>> the loop in build_cp_fntype_variant assumes no duplicate variants, which
>> your patch fixes.
>
> Right, fixup_deferred_exception_variants is only called for fn decls in
> unparsed_noexcepts.
>
>>> The method_type for #1 (I'll mark is as #1 here) is built with it being its own
>>> canonical type.
>>>
>>> The first call to fixup_deferred_exception_variants does not change it: in
>>> there, VARIANT is #1, the loop with 'TYPE_CANONICAL (v) == v' cannot find
>>> an existing variant that would match, so when we do
>>>
>>> v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
>>> rqual, cr, false);
>>> we get #1 so
>>> TYPE_CANONICAL (variant) = v;
>>> is just
>>> TYPE_CANONICAL (#1) = #1;
>>> so no change.
>>>
>>> The second call to fixup_deferred_exception_variants: here we're working with
>>> VARIANT #2. Now we again scan the list of variants {main, #2, #1} where we
>>> find a match for #2: #1. #1's TYPE_CANONICAL is #1 as per above, so we set
>>> TYPE_CANONICAL (#2) = #1;
>>> which I think is correct.
>>>
>>>
>>> I think TYPE_CANONICAL (#3) should also be #1, not #2, which my patch attempts
>>> to do.
>>>
>>>
>>> Hope this explanation makes some sense, please ask away if it doesn't!
>>>
>>>>> 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).
>>>>>
>>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11?
>>>>>
>>>>> 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.c | 16 +++++++++++++++-
>>>>> gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
>>>>> gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
>>>>> 3 files changed, 49 insertions(+), 1 deletion(-)
>>>>> 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.c b/gcc/cp/tree.c
>>>>> index 7f7de86b4e8..2efad49e7c1 100644
>>>>> --- a/gcc/cp/tree.c
>>>>> +++ b/gcc/cp/tree.c
>>>>> @@ -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));
>>>>> @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises)
>>>>> v = build_cp_fntype_variant (TYPE_CANONICAL (variant),
>>>>> rqual, cr, false);
>>>>> TYPE_CANONICAL (variant) = v;
>>>>> +
>>>>> + /* If VARIANT became a duplicate (cp_check_qualified_type-wise)
>>>>> + of an existing variant in the variant list of TYPE after we
>>>>> + have parsed its exception specification, elide it. Otherwise,
>>>>> + build_cp_fntype_variant would use it, leading to "canonical
>>>>> + types differ for identical types." */
>>>>> + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v))
>>>>> + if (v != variant
>>>>> + /* The main variant will not have TYPE_RAISES_EXCEPTIONS
>>>>> + so PREV should never be null. */
>>>>> + && cp_check_qualified_type (v, variant, var_quals,
>>>>> + rqual, cr, false))
>>>>> + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant);
>>
>> I think we don't two loops through the variants. It ought to work to
>> replace the existing loop with yours; if we find v, we prune and use its
>> TYPE_CANONICAL.
>
> Ah yes, good idea; I don't actually need to wait till TYPE_RAISES_EXCEPTIONS
> is set on variant! The following seems to work just as well.
>
> 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 | 16 ++++++++++++++--
> gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++
> gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++
> 3 files changed, 48 insertions(+), 2 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..17436f0512d 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));
> @@ -2815,12 +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);
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.
> && cp_check_qualified_type (v, variant, var_quals,
> rqual, cr, false))
> - break;
> + {
> + /* 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)
> 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: d2ad748eeef0dd260f3993b8dcbffbded3240a0a
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v3] c++: ICE with noexcept and canonical types [PR101715]
2022-01-21 14:27 ` Jason Merrill
@ 2022-01-21 17:42 ` Marek Polacek
2022-01-21 18:08 ` Jason Merrill
0 siblings, 1 reply; 10+ messages in thread
From: Marek Polacek @ 2022-01-21 17:42 UTC (permalink / raw)
To: Jason Merrill; +Cc: Nathan Sidwell, GCC Patches
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
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3] c++: ICE with noexcept and canonical types [PR101715]
2022-01-21 17:42 ` [PATCH v3] " Marek Polacek
@ 2022-01-21 18:08 ` Jason Merrill
0 siblings, 0 replies; 10+ messages in thread
From: Jason Merrill @ 2022-01-21 18:08 UTC (permalink / raw)
To: Marek Polacek; +Cc: Nathan Sidwell, GCC Patches
On 1/21/22 12:42, Marek Polacek wrote:
> 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?
OK, thanks.
> -- >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
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2022-01-21 18:08 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-15 0:22 [PATCH] c++: ICE with noexcept and canonical types [PR101715] Marek Polacek
2022-01-15 14:24 ` Patrick Palka
2022-01-18 16:08 ` Marek Polacek
2022-01-17 18:48 ` Jason Merrill
2022-01-18 16:05 ` Marek Polacek
2022-01-20 20:23 ` Jason Merrill
2022-01-21 1:03 ` [PATCH v2] " Marek Polacek
2022-01-21 14:27 ` Jason Merrill
2022-01-21 17:42 ` [PATCH v3] " Marek Polacek
2022-01-21 18:08 ` Jason Merrill
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