From c7f7c313c0da09232ced316ebb9806bd0f70405c Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Tue, 26 Feb 2019 15:37:39 +0100 Subject: [PATCH] re PR c++/89481 (constexpr function allows writing one active union member and reading another) PR c++/89481 * constexpr.c (cxx_eval_store_expression): When changing active union member, set no_zero_init. * g++.dg/cpp1y/constexpr-89481.C: New test. From-SVN: r269213 --- gcc/cp/ChangeLog | 6 +++++ gcc/cp/constexpr.c | 1 + gcc/testsuite/ChangeLog | 5 ++++ gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C | 24 ++++++++++++++++++++ 4 files changed, 36 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 2da2e3d60dc..6344e4e5feb 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,9 @@ +2019-02-26 Jakub Jelinek + + PR c++/89481 + * constexpr.c (cxx_eval_store_expression): When changing active union + member, set no_zero_init. + 2019-02-23 Marek Polacek PR c++/88294 - ICE with non-constant noexcept-specifier. diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index 40080271c11..5bc5efe4b2c 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -3860,6 +3860,7 @@ cxx_eval_store_expression (const constexpr_ctx *ctx, tree t, } /* Changing active member. */ vec_safe_truncate (CONSTRUCTOR_ELTS (*valp), 0); + no_zero_init = true; } for (idx = 0; diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 3f76c452764..4317ad895ef 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-02-26 Jakub Jelinek + + PR c++/89481 + * g++.dg/cpp1y/constexpr-89481.C: New test. + 2019-02-26 Richard Biener PR tree-optimization/89505 diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C new file mode 100644 index 00000000000..8ac4ef0fd36 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C @@ -0,0 +1,24 @@ +// PR c++/89481 +// { dg-do compile { target c++14 } } + +constexpr int +foo () +{ + union U { long long a; int b[2]; } u { 5LL }; + u.b[1] = 4; // { dg-error "change of the active member of a union from" "" { target c++17_down } } + return u.b[0]; +} + +constexpr int +bar () +{ + union U { long long a; int b[2]; } u { 5LL }; + u.b[1] = 4; // { dg-error "change of the active member of a union from" "" { target c++17_down } } + return u.b[1]; +} + +static_assert (foo () == 0, ""); // { dg-error "non-constant condition for static assertion" } + // { dg-message "in 'constexpr' expansion of" "" { target *-*-* } .-1 } + // { dg-error "accessing uninitialized array element" "" { target c++2a } .-2 } +static_assert (bar () == 4, ""); // { dg-error "non-constant condition for static assertion" "" { target c++17_down } } + // { dg-message "in 'constexpr' expansion of" "" { target c++17_down } .-1 } -- 2.30.2