| Message ID | YeoGcf5zjUzbk9L9@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] c++: ICE with noexcept and canonical types [PR101715] | expand |
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
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)) {}