From ceae6a13366d9646e172fc943fe8e221b70f0920 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Fri, 8 May 2020 11:04:29 -0400 Subject: [PATCH] c++: Parenthesized-init of aggregates accepts invalid code [PR94885] Here we have (conceptually *) something like struct B { }; struct D : B { }; D(0); // invalid and in C++20 the ()-initialization has created a { 0 } constructor that it tries to initialize an object of type D with. We should reject initializing an object of type B from 0, but we wrongly accept it because process_init_constructor_record skips initializers for empty bases/fields: if (DECL_SIZE (field) && integer_zerop (DECL_SIZE (field)) && !TREE_SIDE_EFFECTS (next)) /* Don't add trivial initialization of an empty base/field to the constructor, as they might not be ordered the way the back-end expects. */ continue; but here 'next' was error_mark_node, returned by massage_elt_init, so we wound up with { } which would validly value-initialize the object. [*] Usually digest_init in build_new_method_call_1 would detect this, but in this case the instance is is_dummy_object and we don't call digest just yet. PR c++/94885 * typeck2.c (process_init_constructor_record): Return PICFLAG_ERRONEOUS if an initializer element was erroneous. * g++.dg/cpp2a/paren-init26.C: New test. --- gcc/cp/ChangeLog | 9 +++++++++ gcc/cp/typeck2.c | 6 +++++- gcc/testsuite/g++.dg/cpp2a/paren-init26.C | 14 ++++++++++++++ 3 files changed, 28 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/paren-init26.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 4d0a69c1586c..9a6d647cabbd 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,12 @@ +2020-05-08 Marek Polacek + + Backported from mainline + 2020-05-01 Marek Polacek + + PR c++/94885 + * typeck2.c (process_init_constructor_record): Return PICFLAG_ERRONEOUS + if an initializer element was erroneous. + 2020-05-07 Marek Polacek Backported from mainline diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c index 56fd9bafa7e5..9e5d145a6cd6 100644 --- a/gcc/cp/typeck2.c +++ b/gcc/cp/typeck2.c @@ -1661,7 +1661,11 @@ process_init_constructor_record (tree type, tree init, int nested, int flags, ++idx; } } - if (next) + if (next == error_mark_node) + /* We skip initializers for empty bases/fields, so skipping an invalid + one could make us accept invalid code. */ + return PICFLAG_ERRONEOUS; + else if (next) /* Already handled above. */; else if (DECL_INITIAL (field)) { diff --git a/gcc/testsuite/g++.dg/cpp2a/paren-init26.C b/gcc/testsuite/g++.dg/cpp2a/paren-init26.C new file mode 100644 index 000000000000..0b98ebf43bb6 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/paren-init26.C @@ -0,0 +1,14 @@ +// PR c++/94885 - paren-init of aggregates accepts invalid code. +// { dg-do compile { target c++2a } } + +template // { dg-error "could not convert" } +void foo(); + +struct base {}; +struct derived : base {}; + +void +bar() +{ + foo(); // { dg-error "no matching function" } +} -- 2.47.2