From 1e2fa738e1c67c1ff7242de87a197403b35e8736 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Tue, 29 Oct 2019 21:06:21 +0000 Subject: [PATCH] PR c++/90998 - ICE with copy elision in init by ctor and -Wconversion. After r269667 which introduced joust_maybe_elide_copy, in C++17 we can elide a constructor if it uses a conversion function that returns a prvalue, and use the conversion function in its stead. This eliding means that if we have a candidate that previously didn't have ->second_conv, it can have it after the elision. This confused the -Wconversion warning because it was assuming that if cand1->second_conv is non-null, so is cand2->second_conv. Here cand1->second_conv was non-null but cand2->second_conv remained null, so it crashed in compare_ics. I checked with clang that both compilers call A::operator B() in C++17 and B::B(A const &) otherwise. * call.c (joust): Don't attempt to warn if ->second_conv is null. * g++.dg/cpp0x/overload-conv-4.C: New test. From-SVN: r277593 --- gcc/cp/ChangeLog | 5 +++++ gcc/cp/call.c | 4 +++- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/g++.dg/cpp0x/overload-conv-4.C | 23 ++++++++++++++++++++ 4 files changed, 36 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/overload-conv-4.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index fda743b6872..6b1937557ff 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,8 @@ +2019-10-29 Marek Polacek + + PR c++/90998 - ICE with copy elision in init by ctor and -Wconversion. + * call.c (joust): Don't attempt to warn if ->second_conv is null. + 2019-10-29 Jakub Jelinek PR c++/92201 diff --git a/gcc/cp/call.c b/gcc/cp/call.c index cbd1fe8a0a4..b0c6370107d 100644 --- a/gcc/cp/call.c +++ b/gcc/cp/call.c @@ -10870,7 +10870,9 @@ joust (struct z_candidate *cand1, struct z_candidate *cand2, bool warn, either between a constructor and a conversion op, or between two conversion ops. */ if ((complain & tf_warning) - && winner && warn_conversion && cand1->second_conv + /* In C++17, the constructor might have been elided, which means that + an originally null ->second_conv could become non-null. */ + && winner && warn_conversion && cand1->second_conv && cand2->second_conv && (!DECL_CONSTRUCTOR_P (cand1->fn) || !DECL_CONSTRUCTOR_P (cand2->fn)) && winner != compare_ics (cand1->second_conv, cand2->second_conv)) { diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 3761a99bab1..db443f71729 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-10-29 Marek Polacek + + PR c++/90998 - ICE with copy elision in init by ctor and -Wconversion. + * g++.dg/cpp0x/overload-conv-4.C: New test. + 2019-10-29 Jakub Jelinek PR c++/92201 diff --git a/gcc/testsuite/g++.dg/cpp0x/overload-conv-4.C b/gcc/testsuite/g++.dg/cpp0x/overload-conv-4.C new file mode 100644 index 00000000000..6fcdbbaa6a4 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/overload-conv-4.C @@ -0,0 +1,23 @@ +// PR c++/90998 - ICE with copy elision in init by ctor and -Wconversion. +// { dg-do compile { target c++11 } } +// { dg-options "-Wconversion" } + +struct B; + +struct A { + operator B(); +}; + +struct B { + B(A const &rs); + B(B const &rs); +}; + +B +f (A x) +{ + // C++14: we call B::B(A const &) + // C++17: we call A::operator B() + return B(x); // { dg-warning "choosing .A::operator B\\(\\). over .B::B\\(const A&\\)" "" { target c++17 } } + // { dg-warning "for conversion from .A. to .B." "" { target c++17 } .-1 } +} -- 2.30.2