From 7b521fbd43b3cbaf4313c7719bed72d4de3b49a9 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Wed, 13 Nov 2019 15:59:53 +0000 Subject: [PATCH] PR c++/89070 - bogus [[nodiscard]] warning in SFINAE. This is a complaint that we issue a [[nodiscard]] warning even in SFINAE contexts. Here 'complain' is tf_decltype, but not tf_warning so I guess we can fix it as below. * cvt.c (convert_to_void): Guard maybe_warn_nodiscard calls with tf_warning. * g++.dg/cpp1z/nodiscard7.C: New test. From-SVN: r278147 --- gcc/cp/ChangeLog | 6 ++++++ gcc/cp/cvt.c | 9 ++++++--- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/g++.dg/cpp1z/nodiscard7.C | 18 ++++++++++++++++++ 4 files changed, 35 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1z/nodiscard7.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 5dcf13bbc89..5c9c9f1a7bf 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,9 @@ +2019-11-13 Marek Polacek + + PR c++/89070 - bogus [[nodiscard]] warning in SFINAE. + * cvt.c (convert_to_void): Guard maybe_warn_nodiscard calls with + tf_warning. + 2019-11-13 Richard Sandiford PR c++/92206 diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c index d41aeb8f1fc..23facb77634 100644 --- a/gcc/cp/cvt.c +++ b/gcc/cp/cvt.c @@ -1201,7 +1201,8 @@ convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain) if (DECL_DESTRUCTOR_P (fn)) return expr; - maybe_warn_nodiscard (expr, implicit); + if (complain & tf_warning) + maybe_warn_nodiscard (expr, implicit); break; case INDIRECT_REF: @@ -1357,7 +1358,8 @@ convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain) && !is_reference) warning_at (loc, OPT_Wunused_value, "value computed is not used"); expr = TREE_OPERAND (expr, 0); - if (TREE_CODE (expr) == CALL_EXPR) + if (TREE_CODE (expr) == CALL_EXPR + && (complain & tf_warning)) maybe_warn_nodiscard (expr, implicit); } @@ -1435,7 +1437,8 @@ convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain) AGGR_INIT_EXPR_ARGP (init)); } } - maybe_warn_nodiscard (expr, implicit); + if (complain & tf_warning) + maybe_warn_nodiscard (expr, implicit); break; default:; diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 9e062e799d3..8907e582219 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-11-13 Marek Polacek + + PR c++/89070 - bogus [[nodiscard]] warning in SFINAE. + * g++.dg/cpp1z/nodiscard7.C: New test. + 2019-11-13 Joseph Myers * gcc.dg/c11-float-3.c, gcc.dg/c2x-float-1.c: New tests. diff --git a/gcc/testsuite/g++.dg/cpp1z/nodiscard7.C b/gcc/testsuite/g++.dg/cpp1z/nodiscard7.C new file mode 100644 index 00000000000..80dac63e41e --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/nodiscard7.C @@ -0,0 +1,18 @@ +// PR c++/89070 - bogus [[nodiscard]] warning in SFINAE. +// { dg-do compile { target c++11 } } + +struct A +{ + [[nodiscard]] static int match() { return 42; } +}; + +template +auto g() -> decltype( T::match(), bool() ) +{ + return T::match(); +} + +int main() +{ + g(); +} -- 2.30.2