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