Tested x86_64-pc-linux-gnu, applying to trunk. -- 8< --
The change of active member being non-constant (before C++20) results in a CONSTRUCTOR with a null value for the first field, don't crash. gcc/cp/ChangeLog: * constexpr.cc (free_constructor): Handle null ce->value. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/constexpr-union7.C: New test. --- gcc/cp/constexpr.cc | 2 +- gcc/testsuite/g++.dg/cpp2a/constexpr-union7.C | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-union7.C diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index a673a6022f1..2a6601c0cbc 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -1753,7 +1753,7 @@ free_constructor (tree t) { constructor_elt *ce; for (HOST_WIDE_INT i = 0; vec_safe_iterate (elts, i, &ce); ++i) - if (TREE_CODE (ce->value) == CONSTRUCTOR) + if (ce->value && TREE_CODE (ce->value) == CONSTRUCTOR) vec_safe_push (ctors, ce->value); ggc_free (elts); } diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-union7.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-union7.C new file mode 100644 index 00000000000..230fa6e7d06 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-union7.C @@ -0,0 +1,6 @@ +// { dg-do compile { target c++14 } } +// { dg-options "" } + +union U { int i; float f; }; +constexpr auto g (U u) { return (u.i = 42); } // { dg-error "active member" "" { target c++17_down } } +static_assert (g({.f = 3.14}) == 42); // { dg-error "non-constant" "" { target c++17_down } } base-commit: 9c62af101e11e1cce573c2b3d2e18b403412dbc8 -- 2.39.3