[committed] Avoid -Wunused-value warnings on #pragma omp atomic capture (PR c++/89796)
Jakub Jelinek
jakub@redhat.com
Tue Mar 26 08:13:00 GMT 2019
Hi!
c-omp.c calls omit_one_operand which in several cases can wrap a MODIFY_EXPR
into NON_LVALUE_EXPR and similar. An atomic is always a whole
statement that has its side-effect(s), so -Wunused-value for that is not
really useful.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
committed to trunk, queued for backports.
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.
* g++.dg/gomp/pr89796.C: New test.
* gcc.dg/gomp/pr89796.c: New test.
--- gcc/cp/semantics.c.jj 2019-03-22 15:42:02.469993735 +0100
+++ gcc/cp/semantics.c 2019-03-25 16:51:27.411936064 +0100
@@ -8997,6 +8997,11 @@ finish_omp_atomic (location_t loc, enum
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);
}
--- gcc/testsuite/g++.dg/gomp/pr89796.C.jj 2019-03-25 17:06:08.144778018 +0100
+++ gcc/testsuite/g++.dg/gomp/pr89796.C 2019-03-25 17:04:51.054018606 +0100
@@ -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);
+}
--- gcc/testsuite/gcc.dg/gomp/pr89796.c.jj 2019-03-25 17:06:28.446451316 +0100
+++ gcc/testsuite/gcc.dg/gomp/pr89796.c 2019-03-25 17:05:16.944601962 +0100
@@ -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;
+}
Jakub
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