PR c++/85963 - -Wunused-but-set with ?: in template.

	* pt.c (tsubst_copy_and_build) [COND_EXPR]: Call mark_rvalue_use.

From-SVN: r261458

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9458b4150a83e48ad9d60ced6c496398995f162e..2424a3f6479cf7f462d65d67a5dec4e5ad00f232 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-11  Jason Merrill  <jason@redhat.com>
+
+       PR c++/85963 - -Wunused-but-set with ?: in template.
+       * pt.c (tsubst_copy_and_build) [COND_EXPR]: Call mark_rvalue_use.
+
 2018-06-11  Paolo Carlini  <paolo.carlini@oracle.com>
 
        * decl.c (grok_op_properties): Consistently use the location

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d8880eb138d9ea1e673707e38c1155af654ea77e..ba78d2e34a5668e8f2a19f39f9fdab1fdbacbe85 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -18511,6 +18511,7 @@ tsubst_copy_and_build (tree t,
     case COND_EXPR:
       {
        tree cond = RECUR (TREE_OPERAND (t, 0));
+       cond = mark_rvalue_use (cond);
        tree folded_cond = fold_non_dependent_expr (cond);
        tree exp1, exp2;
 

diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-34.C b/gcc/testsuite/g++.dg/warn/Wunused-var-34.C
new file mode 100644 (file)
index 0000000..52c7151
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-34.C
@@ -0,0 +1,27 @@
+// PR c++/85963
+// { dg-additional-options -Wall }
+
+template<typename T>
+struct foo {
+  T val, alpha;
+  foo() : val(0), alpha(0) {}
+};
+
+template<typename T>
+inline void bar(const foo<T>& A, const foo<T>& B, foo<T>& C) {
+  const bool use_alpha = true;
+  const T        alpha = use_alpha ? (A.alpha * B.alpha) : T(0);
+  
+  C.val   = A.val * B.val;
+  C.alpha = alpha;
+}
+
+
+int main() {
+  foo<double> A,B,C;
+  
+  bar(A,B,C);
+  
+  return 0;
+}
+