From: Jason Merrill <jason@redhat.com>
Date: Tue, 19 Apr 2016 19:30:22 +0000 (-0400)
Subject: PR c++/66543 - -Wunused-but-set* false positives
X-Git-Tag: basepoints/gcc-8~7585
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=76f3944041f68df765cef48819936be04227d696;p=thirdparty%2Fgcc.git

PR c++/66543 - -Wunused-but-set* false positives

	* expr.c (mark_exp_read): Handle NON_DEPENDENT_EXPR.
	* pt.c (make_pack_expansion): Call mark_exp_read.
	* semantics.c (finish_id_expression): Call mark_type_use in
	unevaluated context.

From-SVN: r235221
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7ff3dc573254..73b1cfa21a0e 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,11 @@
 2016-04-19  Jason Merrill  <jason@redhat.com>
 
+	PR c++/66543
+	* expr.c (mark_exp_read): Handle NON_DEPENDENT_EXPR.
+	* pt.c (make_pack_expansion): Call mark_exp_read.
+	* semantics.c (finish_id_expression): Call mark_type_use in
+	unevaluated context.
+
 	DR 2137
 	* call.c (implicit_conversion): If we choose a copy constructor
 	for list-initialization from the same type, the conversion is an
diff --git a/gcc/cp/expr.c b/gcc/cp/expr.c
index 702b717d7abe..61b395300e60 100644
--- a/gcc/cp/expr.c
+++ b/gcc/cp/expr.c
@@ -145,6 +145,7 @@ mark_exp_read (tree exp)
     case ADDR_EXPR:
     case INDIRECT_REF:
     case FLOAT_EXPR:
+    case NON_DEPENDENT_EXPR:
       mark_exp_read (TREE_OPERAND (exp, 0));
       break;
     case COMPOUND_EXPR:
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f9a9d990a46c..e18422f37ecc 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -3696,6 +3696,8 @@ make_pack_expansion (tree arg)
       /* Propagate type and const-expression information.  */
       TREE_TYPE (result) = TREE_TYPE (arg);
       TREE_CONSTANT (result) = TREE_CONSTANT (arg);
+      /* Mark this read now, since the expansion might be length 0.  */
+      mark_exp_read (arg);
     }
   else
     /* Just use structural equality for these TYPE_PACK_EXPANSIONS;
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 56864b4395c5..85ef9934e96f 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3487,6 +3487,12 @@ finish_id_expression (tree id_expression,
       if (!scope && decl != error_mark_node && identifier_p (id_expression))
 	maybe_note_name_used_in_class (id_expression, decl);
 
+      /* A use in unevaluated operand might not be instantiated appropriately
+	 if tsubst_copy builds a dummy parm, or if we never instantiate a
+	 generic lambda, so mark it now.  */
+      if (processing_template_decl && cp_unevaluated_operand)
+	mark_type_use (decl);
+
       /* Disallow uses of local variables from containing functions, except
 	 within lambda-expressions.  */
       if (outer_automatic_var_p (decl))
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-parm-7.C b/gcc/testsuite/g++.dg/warn/Wunused-parm-7.C
new file mode 100644
index 000000000000..ff1dda537d62
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-parm-7.C
@@ -0,0 +1,17 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-but-set-parameter" }
+
+template <typename... Ts> void sink(Ts...);
+
+struct A { int i; };
+
+template <int... I>
+void f(A a)
+{
+  return sink((a.i + I)...);
+}
+
+int main()
+{
+  f<>(A());
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-parm-8.C b/gcc/testsuite/g++.dg/warn/Wunused-parm-8.C
new file mode 100644
index 000000000000..867ad6a2904c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-parm-8.C
@@ -0,0 +1,9 @@
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wunused-but-set-parameter" }
+
+auto l = [](auto t) -> decltype(true ? t : 0) { return {}; };
+
+int main()
+{
+  l(42);
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-24.C b/gcc/testsuite/g++.dg/warn/Wunused-var-24.C
new file mode 100644
index 000000000000..924b2dbc68e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-24.C
@@ -0,0 +1,10 @@
+// PR c++/66543
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wunused-but-set-variable" }
+
+int main() {
+  auto f = []() { };
+  [=](auto) {
+    using Foo = decltype(f());
+  };
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-25.C b/gcc/testsuite/g++.dg/warn/Wunused-var-25.C
new file mode 100644
index 000000000000..959e79cc4164
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-25.C
@@ -0,0 +1,15 @@
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wunused-but-set-variable" }
+
+template <int... I> struct A { };
+template <int... I>
+auto f()
+{
+  constexpr int ar[sizeof...(I)+1] = {I...};
+  return A<ar[I]...>();
+}
+
+int main()
+{
+  f<>();
+}