From a28edad3da5c59f09565d3d42e20be1a924986c4 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Thu, 16 Apr 2020 10:28:23 -0400 Subject: [PATCH] c++: Non-type-dependent variadic lambda init-capture [PR94483] In this PR, we're ICEing on a use of an 'int... a' template parameter pack as part of the variadic lambda init-capture [...z=a]. The unexpected thing about this variadic init-capture is that it is not type-dependent, and so the call to do_auto_deduction from lambda_capture_field_type actually resolves its type to 'int' instead of exiting early like it does for a type-dependent variadic initializer. This later confuses add_capture which, according to one of its comments, assumes that 'type' is always 'auto' for a variadic init-capture. The simplest fix (and the approach that this patch takes) seems to be to avoid doing auto deduction in lambda_capture_field_type when the initializer uses parameter packs, so that we always return 'auto' even in the non-type-dependent case. gcc/cp/ChangeLog: PR c++/94483 * lambda.c (lambda_capture_field_type): Avoid doing auto deduction if the explicit initializer has parameter packs. gcc/testsuite/ChangeLog: PR c++/94483 * g++.dg/cpp2a/lambda-pack-init5.C: New test. --- gcc/cp/ChangeLog | 4 ++++ gcc/cp/lambda.c | 5 ++++- gcc/testsuite/ChangeLog | 3 +++ gcc/testsuite/g++.dg/cpp2a/lambda-pack-init5.C | 18 ++++++++++++++++++ 4 files changed, 29 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-pack-init5.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 465f29090f4..b89b6d88fd3 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,5 +1,9 @@ 2020-04-17 Patrick Palka + PR c++/94483 + * lambda.c (lambda_capture_field_type): Avoid doing auto deduction if + the explicit initializer has parameter packs. + PR c++/88754 * parser.c (cp_parser_check_template_parameters): Before issuing a hard error, first try simulating an error instead. diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c index 4f39f99756b..b55c2f85d27 100644 --- a/gcc/cp/lambda.c +++ b/gcc/cp/lambda.c @@ -223,7 +223,10 @@ lambda_capture_field_type (tree expr, bool explicit_init_p, /* Add the reference now, so deduction doesn't lose outermost CV qualifiers of EXPR. */ type = build_reference_type (type); - type = do_auto_deduction (type, expr, auto_node); + if (uses_parameter_packs (expr)) + /* Stick with 'auto' even if the type could be deduced. */; + else + type = do_auto_deduction (type, expr, auto_node); } else if (!is_this && type_dependent_expression_p (expr)) { diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index b80e7da1c82..030550f1661 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,5 +1,8 @@ 2020-04-17 Patrick Palka + PR c++/94483 + * g++.dg/cpp2a/lambda-pack-init5.C: New test. + PR c++/88754 * g++.dg/parse/ambig10.C: New test. diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init5.C b/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init5.C new file mode 100644 index 00000000000..492fc479e94 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-pack-init5.C @@ -0,0 +1,18 @@ +// PR c++/94483 +// { dg-do compile { target c++2a } } + +template constexpr auto x1 + = [...z = -a] (auto F) { return F(z...); }; + +template constexpr auto x2 + = [&...z = a] (auto F) { return F(z...); }; + +template constexpr auto x3 + = [z = -a] (auto F) { return F(z); }; // { dg-error "packs not expanded" } + + +constexpr auto sum = [] (auto... xs) { return (xs + ... + 0); }; +const int y1 = 1, y2 = 2, y3 = 3; + +static_assert(x1<1,2,3>(sum) == -6); +static_assert(x2(sum) == 6); -- 2.30.2