re PR c++/89796 (Incorrect warning generated with OpenMP atomic capture)

	PR c++/89796
	* semantics.c (finish_omp_atomic): Add warning_sentinel for
	-Wunused-value around finish_expr_stmt call.

	* g++.dg/gomp/pr89796.C: New test.
	* gcc.dg/gomp/pr89796.c: New test.

From-SVN: r269933

5 files changed, 93 insertions, 0 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 703c0f1..80d4ae3 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/89796
+	* semantics.c (finish_omp_atomic): Add warning_sentinel for
+	-Wunused-value around finish_expr_stmt call.
+
 2019-03-25  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/84661
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 15b766d..d7e97e0 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -8997,6 +8997,11 @@ finish_omp_atomic (location_t loc, enum tree_code code, enum tree_code opcode,
       OMP_ATOMIC_MEMORY_ORDER (stmt) = mo;
       SET_EXPR_LOCATION (stmt, loc);
     }
+
+  /* Avoid -Wunused-value warnings here, the whole construct has side-effects
+     and even if it might be wrapped from fold-const.c or c-omp.c wrapped
+     in some tree that appears to be unused, the value is not unused.  */
+  warning_sentinel w (warn_unused_value);
   finish_expr_stmt (stmt);
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ddd5f50..f5d92b6 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/89796
+	* g++.dg/gomp/pr89796.C: New test.
+	* gcc.dg/gomp/pr89796.c: New test.
+
 2019-03-25  David Malcolm  <dmalcolm@redhat.com>
 
 	PR rtl-optimization/88347
diff --git a/gcc/testsuite/g++.dg/gomp/pr89796.C b/gcc/testsuite/g++.dg/gomp/pr89796.C
new file mode 100644
index 0000000..6bbc34e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gomp/pr89796.C
@@ -0,0 +1,53 @@
+// PR c++/89796
+// { dg-do compile }
+// { dg-additional-options "-Wunused-value" }
+
+int
+f1 (int &c)
+{
+  int r;
+  #pragma omp atomic capture	// { dg-bogus "value computed is not used" }
+  { r = c; c++; }
+  return r;
+}
+
+template <int N>
+int
+f2 (int &c)
+{
+  int r;
+  #pragma omp atomic capture	// { dg-bogus "value computed is not used" }
+  { r = c; c++; }
+  return r;
+}
+
+int
+f3 (int &c)
+{
+  return f2 <0> (c);
+}
+
+int
+f4 (int *p)
+{
+  int r;
+  #pragma omp atomic capture	// { dg-bogus "value computed is not used" }
+  { r = *p; (*p)++; }
+  return r;
+}
+
+template <int N>
+int
+f5 (int *p)
+{
+  int r;
+  #pragma omp atomic capture	// { dg-bogus "value computed is not used" }
+  { r = *p; (*p)++; }
+  return r;
+}
+
+int
+f6 (int *p)
+{
+  return f5 <0> (p);
+}
diff --git a/gcc/testsuite/gcc.dg/gomp/pr89796.c b/gcc/testsuite/gcc.dg/gomp/pr89796.c
new file mode 100644
index 0000000..14f5093
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/gomp/pr89796.c
@@ -0,0 +1,23 @@
+/* PR c++/89796 */
+/* { dg-do compile } */
+/* { dg-additional-options "-Wunused-value" } */
+
+int
+f1 (int *p)
+{
+  int r;
+  #pragma omp atomic capture		/* { dg-bogus "value computed is not used" } */
+  { r = *p; (*p)++; }
+  return r;
+}
+
+int
+f2 (int *p)
+{
+  int s
+    = ({ int r;
+	 #pragma omp atomic capture	/* { dg-bogus "value computed is not used" } */
+	 { r = *p; (*p)++; }
+	 r; });
+  return s;
+}