From 267318a2857a42922c3ca033dac4690172b17683 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Wed, 10 Nov 2021 16:42:04 -0500 Subject: c++: constexpr virtual and vbase thunk C++20 allows virtual functions to be constexpr. I don't think that calling through a pointer to a vbase subobject is supposed to work in a constant expression, since an object with virtual bases can't be constant, but the call shouldn't ICE. gcc/cp/ChangeLog: * constexpr.c (cxx_eval_thunk_call): Error instead of ICE on vbase thunk to constexpr function. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/constexpr-virtual20.C: New test. --- gcc/cp/constexpr.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) (limited to 'gcc/cp/constexpr.c') diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index 453007c..7c27131 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -2246,15 +2246,20 @@ cxx_eval_thunk_call (const constexpr_ctx *ctx, tree t, tree thunk_fndecl, { tree function = THUNK_TARGET (thunk_fndecl); - /* virtual_offset is only set in the presence of virtual bases, which make - the class non-literal, so we don't need to handle it here. */ if (THUNK_VIRTUAL_OFFSET (thunk_fndecl)) { - gcc_assert (!DECL_DECLARED_CONSTEXPR_P (function)); if (!ctx->quiet) { - error ("call to non-% function %qD", function); - explain_invalid_constexpr_fn (function); + if (!DECL_DECLARED_CONSTEXPR_P (function)) + { + error ("call to non-% function %qD", function); + explain_invalid_constexpr_fn (function); + } + else + /* virtual_offset is only set for virtual bases, which make the + class non-literal, so we don't need to handle it here. */ + error ("calling constexpr member function %qD through virtual " + "base subobject", function); } *non_constant_p = true; return t; -- cgit v1.1