From 0998d2fd59e7a5eb3a3566c57625702bbdc6a05f Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Wed, 23 Oct 2019 16:41:26 -0400 Subject: [PATCH] Implement P1286R2, Contra CWG1778 The C++11 requirement that an explicit exception-specification on a defaulted function match the implicit one was found to be problematic for std::atomic. This paper, adopted in February, simply removes that requirement: if an explicitly defaulted function has a different exception-specification, that now works just like a user-written function: either it isn't noexcept when it could be, or it is noexcept and will call terminate if an exception is thrown. * method.c (defaulted_late_check): Don't check explicit exception-specification on defaulted function. (after_nsdmi_defaulted_late_checks): Remove. * parser.h (struct cp_unparsed_functions_entry): Remove classes. * parser.c (unparsed_classes): Remove. (push_unparsed_function_queues, cp_parser_class_specifier_1): Adjust. From-SVN: r277351 --- gcc/cp/ChangeLog | 11 ++++ gcc/cp/method.c | 69 +++--------------------- gcc/cp/parser.c | 14 +---- gcc/cp/parser.h | 4 -- gcc/testsuite/g++.dg/DRs/dr1778.C | 7 +++ gcc/testsuite/g++.dg/cpp0x/defaulted23.C | 4 +- gcc/testsuite/g++.dg/cpp0x/defaulted43.C | 10 ++-- 7 files changed, 32 insertions(+), 87 deletions(-) create mode 100644 gcc/testsuite/g++.dg/DRs/dr1778.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index d1518123b24..f587f15ddd7 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,14 @@ +2019-10-23 Jason Merrill + + Implement P1286R2, Contra CWG1778 + * method.c (defaulted_late_check): Don't check explicit + exception-specification on defaulted function. + (after_nsdmi_defaulted_late_checks): Remove. + * parser.h (struct cp_unparsed_functions_entry): Remove classes. + * parser.c (unparsed_classes): Remove. + (push_unparsed_function_queues, cp_parser_class_specifier_1): + Adjust. + 2019-10-23 Jakub Jelinek * constexpr.c (cxx_eval_constant_expression) : diff --git a/gcc/cp/method.c b/gcc/cp/method.c index 73a01147ff9..b613e5df871 100644 --- a/gcc/cp/method.c +++ b/gcc/cp/method.c @@ -2204,40 +2204,12 @@ defaulted_late_check (tree fn) return; } - /* 8.4.2/2: An explicitly-defaulted function (...) may have an explicit - exception-specification only if it is compatible (15.4) with the - exception-specification on the implicit declaration. If a function - is explicitly defaulted on its first declaration, (...) it is - implicitly considered to have the same exception-specification as if - it had been implicitly declared. */ - maybe_instantiate_noexcept (fn); - tree fn_spec = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (fn)); - if (!fn_spec) - { - if (DECL_DEFAULTED_IN_CLASS_P (fn)) - TREE_TYPE (fn) = build_exception_variant (TREE_TYPE (fn), eh_spec); - } - else if (UNEVALUATED_NOEXCEPT_SPEC_P (fn_spec)) - /* Equivalent to the implicit spec. */; - else if (DECL_DEFAULTED_IN_CLASS_P (fn) - && !CLASSTYPE_TEMPLATE_INSTANTIATION (ctx)) - /* We can't compare an explicit exception-specification on a - constructor defaulted in the class body to the implicit - exception-specification until after we've parsed any NSDMI; see - after_nsdmi_defaulted_late_checks. */; - else - { - tree eh_spec = get_defaulted_eh_spec (fn); - if (!comp_except_specs (fn_spec, eh_spec, ce_normal)) - { - if (DECL_DEFAULTED_IN_CLASS_P (fn)) - DECL_DELETED_FN (fn) = true; - else - error ("function %q+D defaulted on its redeclaration " - "with an exception-specification that differs from " - "the implicit exception-specification %qX", fn, eh_spec); - } - } + /* If a function is explicitly defaulted on its first declaration without an + exception-specification, it is implicitly considered to have the same + exception-specification as if it had been implicitly declared. */ + if (!TYPE_RAISES_EXCEPTIONS (TREE_TYPE (fn)) + && DECL_DEFAULTED_IN_CLASS_P (fn)) + TREE_TYPE (fn) = build_exception_variant (TREE_TYPE (fn), eh_spec); if (DECL_DEFAULTED_IN_CLASS_P (fn) && DECL_DECLARED_CONSTEXPR_P (implicit_fn)) @@ -2264,35 +2236,6 @@ defaulted_late_check (tree fn) } } -/* OK, we've parsed the NSDMI for class T, now we can check any explicit - exception-specifications on functions defaulted in the class body. */ - -void -after_nsdmi_defaulted_late_checks (tree t) -{ - if (uses_template_parms (t)) - return; - if (t == error_mark_node) - return; - for (tree fn = TYPE_FIELDS (t); fn; fn = DECL_CHAIN (fn)) - if (!DECL_ARTIFICIAL (fn) - && DECL_DECLARES_FUNCTION_P (fn) - && DECL_DEFAULTED_IN_CLASS_P (fn)) - { - tree fn_spec = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (fn)); - if (UNEVALUATED_NOEXCEPT_SPEC_P (fn_spec)) - continue; - - tree eh_spec = get_defaulted_eh_spec (fn); - if (eh_spec == error_mark_node) - continue; - - if (!comp_except_specs (TYPE_RAISES_EXCEPTIONS (TREE_TYPE (fn)), - eh_spec, ce_normal)) - DECL_DELETED_FN (fn) = true; - } -} - /* Returns true iff FN can be explicitly defaulted, and gives any errors if defaulting FN is ill-formed. */ diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index c597adb38f1..3857fe47d67 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -2005,16 +2005,13 @@ cp_parser_context_new (cp_parser_context* next) parser->unparsed_queues->last ().funs_with_definitions #define unparsed_nsdmis \ parser->unparsed_queues->last ().nsdmis -#define unparsed_classes \ - parser->unparsed_queues->last ().classes #define unparsed_noexcepts \ parser->unparsed_queues->last ().noexcepts static void push_unparsed_function_queues (cp_parser *parser) { - cp_unparsed_functions_entry e = { NULL, make_tree_vector (), NULL, NULL, - NULL }; + cp_unparsed_functions_entry e = { NULL, make_tree_vector (), NULL, NULL }; vec_safe_push (parser->unparsed_queues, e); } @@ -23754,7 +23751,6 @@ cp_parser_class_specifier_1 (cp_parser* parser) error recovery (c++/71169, c++/71832). */ vec_safe_truncate (unparsed_funs_with_default_args, 0); vec_safe_truncate (unparsed_nsdmis, 0); - vec_safe_truncate (unparsed_classes, 0); vec_safe_truncate (unparsed_funs_with_definitions, 0); } @@ -23809,12 +23805,6 @@ cp_parser_class_specifier_1 (cp_parser* parser) if (pushed_scope) pop_scope (pushed_scope); - /* Now do some post-NSDMI bookkeeping. */ - FOR_EACH_VEC_SAFE_ELT (unparsed_classes, ix, class_type) - after_nsdmi_defaulted_late_checks (class_type); - vec_safe_truncate (unparsed_classes, 0); - after_nsdmi_defaulted_late_checks (type); - /* If there are noexcept-specifiers that have not yet been processed, take care of them now. */ class_type = NULL_TREE; @@ -23885,8 +23875,6 @@ cp_parser_class_specifier_1 (cp_parser* parser) cp_parser_late_parsing_for_member (parser, decl); vec_safe_truncate (unparsed_funs_with_definitions, 0); } - else - vec_safe_push (unparsed_classes, type); /* Put back any saved access checks. */ pop_deferring_access_checks (); diff --git a/gcc/cp/parser.h b/gcc/cp/parser.h index 91b5916622d..200498281b5 100644 --- a/gcc/cp/parser.h +++ b/gcc/cp/parser.h @@ -163,10 +163,6 @@ struct GTY(()) cp_unparsed_functions_entry { FIELD_DECLs appear in this list in declaration order. */ vec *nsdmis; - /* Nested classes go in this vector, so that we can do some final - processing after parsing any NSDMIs. */ - vec *classes; - /* Functions with noexcept-specifiers that require post-processing. */ vec *noexcepts; }; diff --git a/gcc/testsuite/g++.dg/DRs/dr1778.C b/gcc/testsuite/g++.dg/DRs/dr1778.C new file mode 100644 index 00000000000..8db937fc0bf --- /dev/null +++ b/gcc/testsuite/g++.dg/DRs/dr1778.C @@ -0,0 +1,7 @@ +// P1286R2: Contra CWG1778 +// { dg-do compile { target c++11 } } + +struct T { T(); T(T &&) noexcept(false); }; +struct U { T t; U(); U(U &&) noexcept = default; }; +U u1; +U u2 = static_cast(u1); // OK, calls std::terminate if T::T(T&&) throws diff --git a/gcc/testsuite/g++.dg/cpp0x/defaulted23.C b/gcc/testsuite/g++.dg/cpp0x/defaulted23.C index dfbdd2f2ed1..23848633c3c 100644 --- a/gcc/testsuite/g++.dg/cpp0x/defaulted23.C +++ b/gcc/testsuite/g++.dg/cpp0x/defaulted23.C @@ -10,10 +10,10 @@ A a; struct B { - B() throw (int) = default; // { dg-message "exception-specification" "" { target { ! c++17 } } } + B() throw (int) = default; }; // { dg-error "dynamic exception specification" "" { target c++17 } .-1 } // { dg-warning "deprecated" "" { target { ! c++17 } } .-2 } -B b; // { dg-error "deleted" "" { target { ! c++17 } } } +B b; struct C { diff --git a/gcc/testsuite/g++.dg/cpp0x/defaulted43.C b/gcc/testsuite/g++.dg/cpp0x/defaulted43.C index f2846fe390c..1fe7818ec67 100644 --- a/gcc/testsuite/g++.dg/cpp0x/defaulted43.C +++ b/gcc/testsuite/g++.dg/cpp0x/defaulted43.C @@ -17,8 +17,8 @@ struct A T t; }; -A::A() noexcept = default; // { dg-error "defaulted" } -A::~A() noexcept = default; // { dg-error "defaulted" } +A::A() noexcept = default; +A::~A() noexcept = default; struct U { @@ -51,10 +51,10 @@ V v; struct C { - C() noexcept = default; // { dg-message "exception-specification" } - ~C() noexcept = default; // { dg-message "exception-specification" } + C() noexcept = default; + ~C() noexcept = default; V v; }; -C c; // { dg-error "deleted" } +C c; -- 2.30.2