From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2122) id E4DB73987C30; Thu, 20 May 2021 21:35:09 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E4DB73987C30 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jason Merrill To: gcc-cvs@gcc.gnu.org Subject: [gcc r10-9846] c++: -Wunused, constant, and generic lambda [PR96311] X-Act-Checkin: gcc X-Git-Author: Jason Merrill X-Git-Refname: refs/heads/releases/gcc-10 X-Git-Oldrev: ff24ef677edee888012aaddeb0ec9bbe366b4f57 X-Git-Newrev: 8909ed58700694f5ba66499739edfea90a0fc813 Message-Id: <20210520213509.E4DB73987C30@sourceware.org> Date: Thu, 20 May 2021 21:35:09 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 May 2021 21:35:10 -0000 https://gcc.gnu.org/g:8909ed58700694f5ba66499739edfea90a0fc813 commit r10-9846-g8909ed58700694f5ba66499739edfea90a0fc813 Author: Jason Merrill Date: Mon Apr 5 16:22:51 2021 -0400 c++: -Wunused, constant, and generic lambda [PR96311] We never called mark_use for a return value in a function with dependent return type. In that situation we don't know if the use is as an rvalue or lvalue, but we can use mark_exp_read instead. gcc/cp/ChangeLog: PR c++/96311 * typeck.c (check_return_expr): Call mark_exp_read in dependent case. gcc/testsuite/ChangeLog: PR c++/96311 * g++.dg/cpp1y/lambda-generic-Wunused.C: New test. Diff: --- gcc/cp/typeck.c | 3 +++ gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c index 6ebf6319efd..a85a75c81ae 100644 --- a/gcc/cp/typeck.c +++ b/gcc/cp/typeck.c @@ -10037,6 +10037,9 @@ check_return_expr (tree retval, bool *no_warning) dependent: /* We should not have changed the return value. */ gcc_assert (retval == saved_retval); + /* We don't know if this is an lvalue or rvalue use, but + either way we can mark it as read. */ + mark_exp_read (retval); return retval; } diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C new file mode 100644 index 00000000000..b43cbe6b675 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C @@ -0,0 +1,18 @@ +// PR c++/96311 +// { dg-do compile { target c++14 } } +// { dg-additional-options -Wunused } + +auto foo() +{ + constexpr int used = 0; + return + [](auto unused) + { + return used; + }; +} + +int main() +{ + foo()(42); +}