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* [gcc r10-9846] c++: -Wunused, constant, and generic lambda [PR96311]
@ 2021-05-20 21:35 Jason Merrill
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From: Jason Merrill @ 2021-05-20 21:35 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:8909ed58700694f5ba66499739edfea90a0fc813
commit r10-9846-g8909ed58700694f5ba66499739edfea90a0fc813
Author: Jason Merrill <jason@redhat.com>
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);
+}
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