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Re: [C++ PATCH] Avoid bogus -Wunused-but-set* with structured binding (PR c++/85952)
On Tue, May 29, 2018 at 10:49:03AM -0400, Jason Merrill wrote:
> >> auto & [x,y] = a;
> >>
> >> but that should be added to the testcase.
> >
> > It is already there (in baz).
>
> Well, yes, but in baz a is an S, not an array; I see value and
> reference cases for S, but only value for int array.
Oops, yes, you're right. Added qux then that tests array initializer
and & qualifier.
Ok with that change?
2018-05-29 Jakub Jelinek <jakub@redhat.com>
PR c++/85952
* init.c (build_aggr_init): For structured binding initialized from
array call mark_rvalue_use on the initializer.
* g++.dg/warn/Wunused-var-33.C: New test.
--- gcc/cp/init.c.jj 2018-05-25 14:34:41.000000000 +0200
+++ gcc/cp/init.c 2018-05-28 19:04:10.504063972 +0200
@@ -1678,6 +1678,7 @@ build_aggr_init (tree exp, tree init, in
if (VAR_P (exp) && DECL_DECOMPOSITION_P (exp))
{
from_array = 1;
+ init = mark_rvalue_use (init);
if (init && DECL_P (init)
&& !(flags & LOOKUP_ONLYCONVERTING))
{
--- gcc/testsuite/g++.dg/warn/Wunused-var-33.C.jj 2018-05-28 19:32:00.236440573 +0200
+++ gcc/testsuite/g++.dg/warn/Wunused-var-33.C 2018-05-29 16:52:21.322700629 +0200
@@ -0,0 +1,37 @@
+// PR c++/85952
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-but-set-variable" }
+
+int
+foo ()
+{
+ int a[2] = {1, 2}; // { dg-bogus "set but not used" } */
+ auto [x, y] = a; // { dg-warning "structured bindings only available with" "" { target c++14_down } }
+ return x + y;
+}
+
+struct S { int d, e; };
+
+int
+bar ()
+{
+ S a = {1, 2};
+ auto [x, y] = a; // { dg-warning "structured bindings only available with" "" { target c++14_down } }
+ return x + y;
+}
+
+int
+baz ()
+{
+ S a = {1, 2};
+ auto & [x, y] = a; // { dg-warning "structured bindings only available with" "" { target c++14_down } }
+ return x + y;
+}
+
+int
+qux ()
+{
+ int a[2] = {1, 2};
+ auto & [x, y] = a; // { dg-warning "structured bindings only available with" "" { target c++14_down } }
+ return x + y;
+}
Jakub