Hi!
Jason's recent change removed a mark_rvalue_use call from constant_value_1,
which unfortunately regressed quite a few cases where
-Wunused-but-set-variable now has false positives.
The easiest fix seems to be just deal with the -Wunused-but-set-variable
issue at that point.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-01-05 Jakub Jelinek <ja...@redhat.com>
PR c++/82728
PR c++/82799
PR c++/83690
* init.c (constant_value_1): Call mark_exp_read on decl.
* g++.dg/warn/Wunused-var-27.C: New test.
* g++.dg/warn/Wunused-var-28.C: New test.
* g++.dg/warn/Wunused-var-29.C: New test.
--- gcc/cp/init.c.jj 2018-01-03 10:20:17.296537499 +0100
+++ gcc/cp/init.c 2018-01-05 16:48:27.914911810 +0100
@@ -2211,6 +2211,7 @@ constant_value_1 (tree decl, bool strict
initializer for the static data member is not processed
until needed; we need it now. */
mark_used (decl, tf_none);
+ mark_exp_read (decl);
init = DECL_INITIAL (decl);
if (init == error_mark_node)
{
--- gcc/testsuite/g++.dg/warn/Wunused-var-27.C.jj 2018-01-05
16:44:15.647814313 +0100
+++ gcc/testsuite/g++.dg/warn/Wunused-var-27.C 2018-01-05 16:44:05.774810218
+0100
@@ -0,0 +1,14 @@
+// PR c++/82728
+// { dg-do compile }
+// { dg-options "-Wunused-but-set-variable" }
+
+void
+foo ()
+{
+ const int i = 1; // { dg-bogus "set but not used" }
+ switch (0)
+ {
+ case i:
+ break;
+ }
+}
--- gcc/testsuite/g++.dg/warn/Wunused-var-28.C.jj 2018-01-05
16:44:27.158819090 +0100
+++ gcc/testsuite/g++.dg/warn/Wunused-var-28.C 2018-01-05 16:42:18.766765787
+0100
@@ -0,0 +1,15 @@
+// PR c++/82799
+// { dg-do compile }
+// { dg-options "-Wunused-but-set-variable" }
+
+enum E { b };
+struct C {
+ template <E>
+ int foo ()
+ {
+ const bool i = 0; // { dg-bogus "set but not used" }
+ const int r = i ? 7 : 9;
+ return r;
+ }
+ void bar () { foo <b> (); }
+};
--- gcc/testsuite/g++.dg/warn/Wunused-var-29.C.jj 2018-01-05
16:45:59.576857460 +0100
+++ gcc/testsuite/g++.dg/warn/Wunused-var-29.C 2018-01-05 16:45:42.956850557
+0100
@@ -0,0 +1,10 @@
+// PR c++/83690
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-but-set-variable" }
+
+void
+foo ()
+{
+ constexpr bool foo = true; // { dg-bogus "set but not used" }
+ static_assert (foo, "foo");
+}
Jakub
