On 5/25/21 11:10 AM, Jakub Jelinek wrote:
On Tue, May 25, 2021 at 09:40:13AM -0400, Jason Merrill wrote:
Please also test the case of a [[nodiscard]] function returning an empty
class type.
Here it is. I have also extended the decltype(nullptr) nodiscard test.
Retested on x86_64-linux (nothing other than testcases changed), ok for
trunk?
OK.
2021-05-25 Jakub Jelinek <ja...@redhat.com>
PR c++/100666
* call.c (convert_arg_to_ellipsis): For expressions with NULLPTR_TYPE
and side-effects, temporarily disable -Wunused-result warning when
building COMPOUND_EXPR.
* g++.dg/cpp1z/nodiscard8.C: New test.
* g++.dg/cpp1z/nodiscard9.C: New test.
--- gcc/cp/call.c.jj 2021-05-25 10:55:55.105239017 +0200
+++ gcc/cp/call.c 2021-05-25 17:01:47.524719692 +0200
@@ -8178,7 +8178,10 @@ convert_arg_to_ellipsis (tree arg, tsubs
{
arg = mark_rvalue_use (arg);
if (TREE_SIDE_EFFECTS (arg))
- arg = cp_build_compound_expr (arg, null_pointer_node, complain);
+ {
+ warning_sentinel w(warn_unused_result);
+ arg = cp_build_compound_expr (arg, null_pointer_node, complain);
+ }
else
arg = null_pointer_node;
}
--- gcc/testsuite/g++.dg/cpp1z/nodiscard8.C.jj 2021-05-25 17:01:47.524719692
+0200
+++ gcc/testsuite/g++.dg/cpp1z/nodiscard8.C 2021-05-25 17:04:34.668904548
+0200
@@ -0,0 +1,15 @@
+// PR c++/100666
+// { dg-do compile { target c++11 } }
+
+[[nodiscard]] decltype(nullptr) bar ();
+extern void foo (...);
+template <typename T> void qux (T);
+
+void
+baz ()
+{
+ foo (bar ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ bar (); // { dg-warning "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ auto x = bar (); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ qux (bar ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+}
--- gcc/testsuite/g++.dg/cpp1z/nodiscard9.C.jj 2021-05-25 17:05:01.907608730
+0200
+++ gcc/testsuite/g++.dg/cpp1z/nodiscard9.C 2021-05-25 17:06:40.054542742
+0200
@@ -0,0 +1,22 @@
+// PR c++/100666
+// { dg-do compile { target c++11 } }
+
+struct S {};
+[[nodiscard]] S bar ();
+struct U { S s; };
+[[nodiscard]] U corge ();
+extern void foo (...);
+template <typename T> void qux (T);
+
+void
+baz ()
+{
+ foo (bar ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ bar (); // { dg-warning "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ auto x = bar (); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ qux (bar ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ foo (corge ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ corge (); // { dg-warning "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ auto y = corge (); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+ qux (corge ()); // { dg-bogus "ignoring return value of '\[^\n\r]*',
declared with attribute 'nodiscard'" }
+}
Jakub
