From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1888) id 57A5A3858D33; Thu, 2 Mar 2023 19:05:06 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 57A5A3858D33 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1677783906; bh=gdArifG6+4Y2c3Q2sd+oSZ3S97GDFqS3JvjnlMM01AA=; h=From:To:Subject:Date:From; b=eF3OJis9z6TALA6IjapxO8lKMIR2w1sMozsleW8awETPZPoAwUJqU5OmKpWtI+Iki 9CgCD9GF5iS/rkAYCKiAUMT+oguHwTXsXsHVdcMkMJEq+iw9uq5u4eNiwoMs7SoZYS ndk01ZPwgKtPV+aQVgFS8DDSQwugzI3R1YX17SFw= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Patrick Palka To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-6421] c++: constant non-copy-init is manifestly constant [PR108243] X-Act-Checkin: gcc X-Git-Author: Patrick Palka X-Git-Refname: refs/heads/master X-Git-Oldrev: 20bd258d0fa09837b3a93478ef92d8789cbcd442 X-Git-Newrev: cbaa1d9c218d9c0b5e34e510a462ff4e299a0f3f Message-Id: <20230302190506.57A5A3858D33@sourceware.org> Date: Thu, 2 Mar 2023 19:05:06 +0000 (GMT) List-Id: https://gcc.gnu.org/g:cbaa1d9c218d9c0b5e34e510a462ff4e299a0f3f commit r13-6421-gcbaa1d9c218d9c0b5e34e510a462ff4e299a0f3f Author: Patrick Palka Date: Thu Mar 2 14:03:21 2023 -0500 c++: constant non-copy-init is manifestly constant [PR108243] According to [basic.start.static]/2 and [expr.const]/2, a variable with static storage duration initialized with a constant initializer has constant initialization, and such an initializer is manifestly constant-evaluated. For copy initialization, we're already getting this right because in that case check_initializer would consistently call store_init_value, which for TREE_STATIC variables calls fold_non_dependent_init with m_c_e=true. But for direct (or default) initialization, check_initializer doesn't always call store_init_value. We instead however always call maybe_constant_init from expand_default_init[1], albeit with m_c_e=false which means we don't get the "manifestly constant-evaluated" part right for non-copy-init. This patch fixes this by setting m_c_e=true in maybe_constant_init for static storage duration variables, mainly for benefit of the call to maybe_constant_init from expand_default_init. [1]: this maybe_constant_init call isn't reached in the copy-init case because there init is a CONSTRUCTOR rather than a TREE_LIST, and so we exit early from expand_default_init, returning an INIT_EXPR. This INIT_EXPR is ultimately what causes us to consistently hit the store_init_value code path from check_initializer in the copy-init case. PR c++/108243 gcc/cp/ChangeLog: * constexpr.cc (maybe_constant_init_1): Override manifestly_const_eval to true if is_static. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/is-constant-evaluated14.C: New test. Diff: --- gcc/cp/constexpr.cc | 2 + .../g++.dg/cpp2a/is-constant-evaluated14.C | 140 +++++++++++++++++++++ 2 files changed, 142 insertions(+) diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 0770cdcd768..acf9847a4d1 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -8770,6 +8770,8 @@ maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant, shouldn't bend the rules the same way for automatic variables. */ bool is_static = (decl && DECL_P (decl) && (TREE_STATIC (decl) || DECL_EXTERNAL (decl))); + if (is_static) + manifestly_const_eval = true; t = cxx_eval_outermost_constant_expr (t, allow_non_constant, !is_static, mce_value (manifestly_const_eval), false, decl); diff --git a/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated14.C b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated14.C new file mode 100644 index 00000000000..a41461f3604 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated14.C @@ -0,0 +1,140 @@ +// PR c++/108243 +// Verify a variable with static storage duration initialized with a +// constant initializer has constant initialization, and the initializer +// is manifestly constant-evaluated. +// { dg-do run { target c++11 } } +// { dg-additional-options "-fdump-tree-original" } + +// { dg-final { scan-tree-dump-not "static initializers for" "original" } } +// { dg-final { scan-tree-dump-not "cxa_guard_acquire" "original" } } + +#include + +struct A { + constexpr A(int n) : n(n), m(__builtin_is_constant_evaluated()) { } + constexpr A() : A(42) { } + void verify_mce() const { + if (m != 1) __builtin_abort(); + } + int n; + int m; +}; + +A a1 = {42}; +A a2{42}; +A a3(42); +A a4; +A a5{}; + +void f() { + static A a1 = {42}; + static A a2{42}; + static A a3(42); + static A a4; + static A a5{}; + for (auto& a : {a1, a2, a3, a4, a5}) + a.verify_mce(); +} + +template +void g() { + static A a1 = {42}; + static A a2{42}; + static A a3(42); + static A a4; + static A a5{}; + static A a6 = {N...}; + static A a7{N...}; + static A a8(N...); + for (auto& a : {a1, a2, a3, a4, a5, a6, a7, a8}) + a.verify_mce(); +} + +struct B { + static A a1; + static A a2; + static A a3; + static A a4; + static A a5; + static void verify_mce() { + for (auto& a : {a1, a2, a3, a4, a5}) + a.verify_mce(); + } +}; + +A B::a1 = {42}; +A B::a2{42}; +A B::a3(42); +A B::a4; +A B::a5{}; + +template +struct BT { + static A a1; + static A a2; + static A a3; + static A a4; + static A a5; + static A a6; + static A a7; + static A a8; + static void verify_mce() { + for (auto& a : {a1, a2, a3, a4, a5}) + a.verify_mce(); + } +}; + +template A BT::a1 = {42}; +template A BT::a2{42}; +template A BT::a3(42); +template A BT::a4; +template A BT::a5{}; +template A BT::a6 = {N...}; +template A BT::a7{N...}; +template A BT::a8(N...); + +#if __cpp_inline_variables +struct BI { + static inline A a1 = {42}; + static inline A a2{42}; + static inline A a3; + static inline A a4{}; + static void verify_mce() { + for (auto& a : {a1, a2, a3, a4}) + a.verify_mce(); + } +}; + +template +struct BIT { + static inline A a1 = {42}; + static inline A a2{42}; + static inline A a3; + static inline A a4{}; + static inline A a5 = {N...}; + static inline A a6{N...}; + static void verify_mce() { + for (auto& a : {a1, a2, a3, a4, a5, a6}) + a.verify_mce(); + } +}; +#endif + +int main() { + for (auto& a : {a1, a2, a3, a4, a5}) + a.verify_mce(); + + f(); + g<42>(); + g<>(); + + B::verify_mce(); + BT<42>::verify_mce(); + BT<>::verify_mce(); + +#if __cpp_inline_variables + BI::verify_mce(); + BIT<42>::verify_mce(); + BIT<>::verify_mce(); +#endif +}