From 3bfa96895b3219afd93a7038850baef4b63c1f82 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Thu, 18 Feb 2021 16:21:52 +0100 Subject: [PATCH] c++: Fix -std=c++20 ICE on virtual method call [PR99132] On the following testcase we ICE in C++20 mode during cp_get_callee_fndecl -> constexpr evaluation. It is only in C++20 mode on this testcase because virtual methods can't be constexpr in C++17 and earlier and so potential_constant_expression_1 rejects it earlier. And the ICE is caused by genericization changing the h PARM_DECL from having B type to B & DECL_BY_REFERENCE and the constexpr evaluation not being able to deal with that. I think this just shows that we shouldn't do the constexpr evaluation during genericization and later, and other spots e.g. during gimplification also don't call cp_get_callee_fndecl but cp_get_callee_fndecl_nofold. After all, cp_fold has already been run and it did the folding if there was any opportunity to do so. And furthermore, what that cp_genericize_r spot does is check for any left-over immediate function calls (which can be ATM just std::source_location::current() call) and immediate functions outside of immediate functions can't have addresses leaked into the IL, so it will be always a direct call anyway. And immediate functions themselves don't make it into genericization/gimplification. 2021-02-18 Jakub Jelinek PR c++/99132 * cp-gimplify.c (cp_genericize_r) : Use cp_get_callee_fndecl_nofold instead of cp_get_callee_fndecl to check for immediate function calls. * g++.dg/cpp2a/constexpr-virtual18.C: New test. --- gcc/cp/cp-gimplify.c | 2 +- gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C | 13 +++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c index 1c5e15b957f..abb8a6ef078 100644 --- a/gcc/cp/cp-gimplify.c +++ b/gcc/cp/cp-gimplify.c @@ -1386,7 +1386,7 @@ cp_genericize_r (tree *stmt_p, int *walk_subtrees, void *data) break; } - if (tree fndecl = cp_get_callee_fndecl (stmt)) + if (tree fndecl = cp_get_callee_fndecl_nofold (stmt)) if (DECL_IMMEDIATE_FUNCTION_P (fndecl)) { gcc_assert (source_location_current_p (fndecl)); diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C new file mode 100644 index 00000000000..2fbf0b22da3 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-virtual18.C @@ -0,0 +1,13 @@ +// PR c++/99132 +// { dg-do compile { target c++11 } } + +template struct A { T c; }; +template struct B { + A d; + constexpr T operator-> () { return d.c; } + B (B &&); +}; +struct C { + virtual void foo (); + void bar (B h) { h->foo (); } +}; -- 2.30.2