From ac0bc21bd634a334ba8f323c39a11f01dfdc2aae Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Tue, 1 Jun 2021 12:23:49 -0400 Subject: [PATCH] c++: value-init vs zero-init in expand_aggr_init_1 [PR65816] In the case of value-initializing an object of class type T, [dcl.init.general]/8 says: - if T has either no default constructor ([class.default.ctor]) or a default constructor that is user-provided or deleted, then the object is default-initialized; - otherwise, the object is zero-initialized and ... if T has a non-trivial default constructor, the object is default-initialized; But when determining whether to first zero-initialize the object, expand_aggr_init_1 incorrectly considers the user-providedness of _all_ constructors rather than only that of the _default_ constructors. This causes us to skip the zero-initialization step when the class type has a defaulted default constructor alongside a user-defined constructor. It seems the predicate type_has_non_user_provided_default_constructor accurately captures the above rule for when to first perform a zero-initialization during value-initialization, so this patch adjusts expand_aggr_init_1 to use this predicate instead. PR c++/65816 gcc/cp/ChangeLog: * init.c (expand_aggr_init_1): Check type_has_non_user_provided_default_constructor instead of type_has_user_provided_constructor. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-delegating3.C: New test. * g++.dg/cpp0x/dc10.C: New test. * g++.dg/cpp0x/initlist-base4.C: New test. * g++.dg/cpp2a/constexpr-init22.C: New test. libstdc++-v3/ChangeLog: * testsuite/23_containers/deque/allocator/default_init.cc, testsuite/23_containers/forward_list/allocator/default_init.cc, testsuite/23_containers/list/allocator/default_init.cc, testsuite/23_containers/map/allocator/default_init.cc, testsuite/23_containers/set/allocator/default_init.cc, testsuite/23_containers/vector/allocator/default_init.cc, testsuite/23_containers/vector/bool/allocator/default_init.cc: Remove xfail. --- gcc/cp/init.c | 4 +-- .../g++.dg/cpp0x/constexpr-delegating3.C | 10 +++++++ gcc/testsuite/g++.dg/cpp0x/dc10.C | 19 ++++++++++++++ gcc/testsuite/g++.dg/cpp0x/initlist-base4.C | 26 +++++++++++++++++++ gcc/testsuite/g++.dg/cpp2a/constexpr-init22.C | 14 ++++++++++ .../deque/allocator/default_init.cc | 1 - .../forward_list/allocator/default_init.cc | 1 - .../list/allocator/default_init.cc | 1 - .../map/allocator/default_init.cc | 1 - .../set/allocator/default_init.cc | 1 - .../vector/allocator/default_init.cc | 1 - .../vector/bool/allocator/default_init.cc | 1 - 12 files changed, 71 insertions(+), 9 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-delegating3.C create mode 100644 gcc/testsuite/g++.dg/cpp0x/dc10.C create mode 100644 gcc/testsuite/g++.dg/cpp0x/initlist-base4.C create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-init22.C diff --git a/gcc/cp/init.c b/gcc/cp/init.c index 04d495807ef..b1123287300 100644 --- a/gcc/cp/init.c +++ b/gcc/cp/init.c @@ -2078,9 +2078,9 @@ expand_aggr_init_1 (tree binfo, tree true_exp, tree exp, tree init, int flags, that's value-initialization. */ if (init == void_type_node) { - /* If the type has data but no user-provided ctor, we need to zero + /* If the type has data but no user-provided default ctor, we need to zero out the object. */ - if (!type_has_user_provided_constructor (type) + if (type_has_non_user_provided_default_constructor (type) && !is_really_empty_class (type, /*ignore_vptr*/true)) { tree field_size = NULL_TREE; diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-delegating3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-delegating3.C new file mode 100644 index 00000000000..2263ec89488 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-delegating3.C @@ -0,0 +1,10 @@ +// PR c++/65816 +// { dg-do compile { target c++11 } } + +struct test { + int m; + test() = default; + constexpr test(int) : test() {} +}; + +static_assert(test(0).m == 0, ""); diff --git a/gcc/testsuite/g++.dg/cpp0x/dc10.C b/gcc/testsuite/g++.dg/cpp0x/dc10.C new file mode 100644 index 00000000000..c008a1703e8 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/dc10.C @@ -0,0 +1,19 @@ +// PR c++/65816 +// { dg-do run { target c++11 } } + +void* operator new(decltype(sizeof(int)), void* ptr) { return ptr; } + +struct test { + int i; + test() = default; + test(int) : test() {} +}; + +int main() { + alignas(test) unsigned char space[sizeof(test)]; + for (auto& c : space) c = 0xff; + + auto ptr = ::new(&space) test(42); + int& i = static_cast(*ptr).i; + if (i != 0) __builtin_abort(); +} diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-base4.C b/gcc/testsuite/g++.dg/cpp0x/initlist-base4.C new file mode 100644 index 00000000000..4a02af92799 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/initlist-base4.C @@ -0,0 +1,26 @@ +// PR c++/65816 +// { dg-do run { target c++11 } } + +void* operator new(decltype(sizeof(int)), void* ptr) { return ptr; } + +struct item { int i; }; + +struct collector : item { + int j; + collector() = default; + collector(int) {} +}; + +struct tuple : collector { + tuple() : collector() {} +}; + +int main() { + alignas(tuple) unsigned char space[sizeof(tuple)]; + for (auto& c : space) c = 0xff; + + auto ptr = ::new(&space) tuple; + int& i = static_cast(*ptr).i; + int& j = static_cast(*ptr).j; + if (i != 0 || j != 0) __builtin_abort(); +} diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-init22.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-init22.C new file mode 100644 index 00000000000..50e4a95dbda --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-init22.C @@ -0,0 +1,14 @@ +// PR c++/65816 +// { dg-do compile { target c++20 } } + +struct X { + int i; + X() = default; + constexpr X(int) { } +}; + +struct Y : X { + constexpr Y() : X() { } +}; + +static_assert(Y().i == 0); diff --git a/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc index f51cc5b49b9..9428206f2ef 100644 --- a/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc index a60192641d4..4298fa5ffa5 100644 --- a/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/list/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/list/allocator/default_init.cc index 62bfd78df18..03d8cfc89e8 100644 --- a/libstdc++-v3/testsuite/23_containers/list/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/list/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/map/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/map/allocator/default_init.cc index bc9027703fc..6e3f36d60a4 100644 --- a/libstdc++-v3/testsuite/23_containers/map/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/map/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/set/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/set/allocator/default_init.cc index 8a99b491c25..b031cb81504 100644 --- a/libstdc++-v3/testsuite/23_containers/set/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/set/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/vector/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/vector/allocator/default_init.cc index c16d3b046e4..4673db71b6c 100644 --- a/libstdc++-v3/testsuite/23_containers/vector/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/vector/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/default_init.cc index 4111e3ac3eb..61cc7859d74 100644 --- a/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/default_init.cc +++ b/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/default_init.cc @@ -17,7 +17,6 @@ // { dg-do run { target c++11 } } // { dg-options "-O0" } -// { dg-xfail-run-if "PR c++/65816" { *-*-* } } #include #include