From 5c64df80df274c753bfc8415bd902e1180e76f6a Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Mon, 10 Aug 2020 17:53:46 +0200 Subject: [PATCH] c++: Fix constexpr evaluation of SPACESHIP_EXPR [PR96497] The following valid testcase is rejected, because cxx_eval_binary_expression is called on the SPACESHIP_EXPR with lval = true, as the address of the spaceship needs to be passed to a method call. After recursing on the operands and calling genericize_spaceship which turns it into a TARGET_EXPR with initialization, we call cxx_eval_constant_expression on it which succeeds, but then we fall through into code that will VERIFY_CONSTANT (r) which FAILs because it is an address of a variable. Rather than avoiding that for lval = true and SPACESHIP_EXPR, the patch just tail calls cxx_eval_constant_expression - I believe that call should perform all the needed verifications. 2020-08-10 Jakub Jelinek PR c++/96497 * constexpr.c (cxx_eval_binary_expression): For SPACESHIP_EXPR, tail call cxx_eval_constant_expression after genericize_spaceship to avoid undesirable further VERIFY_CONSTANT. * g++.dg/cpp2a/spaceship-constexpr3.C: New test. --- gcc/cp/constexpr.c | 4 ++-- gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C | 7 +++++++ 2 files changed, 9 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index ab747a58fa0..8ee0f2abe1a 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -3085,8 +3085,8 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t, else if (code == SPACESHIP_EXPR) { r = genericize_spaceship (type, lhs, rhs); - r = cxx_eval_constant_expression (ctx, r, lval, non_constant_p, - overflow_p); + return cxx_eval_constant_expression (ctx, r, lval, non_constant_p, + overflow_p); } if (r == NULL_TREE) diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C b/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C new file mode 100644 index 00000000000..95f03e6e231 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C @@ -0,0 +1,7 @@ +// PR c++/96497 +// { dg-do compile { target c++20 } } + +#include + +static_assert(std::partial_ordering(std::strong_ordering::less) < 0); +static_assert(std::partial_ordering(1 <=> 2) < 0); -- 2.30.2