From: Marek Polacek <polacek@redhat.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>, Jason Merrill <jason@redhat.com>
Subject: [PATCH] c++: Tweaks for -Wredundant-move [PR107363]
Date: Fri, 28 Oct 2022 16:42:33 -0400 [thread overview]
Message-ID: <20221028204233.409310-1-polacek@redhat.com> (raw)
Two things here:
1) when we're pointing out that std::move on a constant object is
redundant, don't say "in return statement" when we aren't in a
return statement;
2) suppress the warning when the std::move call was dependent, because
removing the std::move may not be correct for a different
instantiation of the original template.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/107363
gcc/cp/ChangeLog:
* semantics.cc (finish_call_expr): Suppress OPT_Wpessimizing_move.
* typeck.cc (maybe_warn_pessimizing_move): Check warn_redundant_move
and warning_suppressed_p. Adjust a message depending on return_p.
(check_return_expr): Don't suppress OPT_Wpessimizing_move here.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/Wredundant-move13.C: New test.
---
gcc/cp/semantics.cc | 4 ++
gcc/cp/typeck.cc | 16 ++---
.../g++.dg/cpp0x/Wredundant-move13.C | 61 +++++++++++++++++++
3 files changed, 73 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/Wredundant-move13.C
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 36aa9c4499f..caaa40fde19 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2738,6 +2738,10 @@ finish_call_expr (tree fn, vec<tree, va_gc> **args, bool disallow_virtual,
result = build_min_nt_call_vec (orig_fn, *args);
SET_EXPR_LOCATION (result, cp_expr_loc_or_input_loc (fn));
KOENIG_LOOKUP_P (result) = koenig_p;
+ /* Disable the std::move warnings since this call was dependent
+ (c++/89780, c++/107363). This also suppresses the
+ -Wredundant-move warning. */
+ suppress_warning (result, OPT_Wpessimizing_move);
if (is_overloaded_fn (fn))
fn = get_fns (fn);
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 2e0fd8fbf17..5f5fb2a212b 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10885,7 +10885,9 @@ maybe_warn_pessimizing_move (tree expr, tree type, bool return_p)
and where the std::move does nothing if T does not have a T(const T&&)
constructor, because the argument is const. It will not use T(T&&)
because that would mean losing the const. */
- else if (TYPE_REF_P (TREE_TYPE (arg))
+ else if (warn_redundant_move
+ && !warning_suppressed_p (expr, OPT_Wredundant_move)
+ && TYPE_REF_P (TREE_TYPE (arg))
&& CP_TYPE_CONST_P (TREE_TYPE (TREE_TYPE (arg))))
{
tree rtype = TREE_TYPE (TREE_TYPE (arg));
@@ -10901,8 +10903,11 @@ maybe_warn_pessimizing_move (tree expr, tree type, bool return_p)
return;
}
auto_diagnostic_group d;
- if (warning_at (loc, OPT_Wredundant_move,
- "redundant move in return statement"))
+ if (return_p
+ ? warning_at (loc, OPT_Wredundant_move,
+ "redundant move in return statement")
+ : warning_at (loc, OPT_Wredundant_move,
+ "redundant move in initialization"))
inform (loc, "remove %<std::move%> call");
}
}
@@ -11126,11 +11131,6 @@ check_return_expr (tree retval, bool *no_warning)
/* We don't know if this is an lvalue or rvalue use, but
either way we can mark it as read. */
mark_exp_read (retval);
- /* Disable our std::move warnings when we're returning
- a dependent expression (c++/89780). */
- if (retval && TREE_CODE (retval) == CALL_EXPR)
- /* This also suppresses -Wredundant-move. */
- suppress_warning (retval, OPT_Wpessimizing_move);
return retval;
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/Wredundant-move13.C b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move13.C
new file mode 100644
index 00000000000..80e7d80cd02
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move13.C
@@ -0,0 +1,61 @@
+// PR c++/107363
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wredundant-move" }
+
+// Define std::move.
+namespace std {
+ template<typename _Tp>
+ struct remove_reference
+ { typedef _Tp type; };
+
+ template<typename _Tp>
+ struct remove_reference<_Tp&>
+ { typedef _Tp type; };
+
+ template<typename _Tp>
+ struct remove_reference<_Tp&&>
+ { typedef _Tp type; };
+
+ template<typename _Tp>
+ constexpr typename std::remove_reference<_Tp>::type&&
+ move(_Tp&& __t) noexcept
+ { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
+}
+
+template <typename T, typename U>
+struct Optional {
+ U &value();
+ T release_value() {
+ T t = std::move (value ());
+ return t;
+ }
+};
+
+struct Foo {};
+void test(Optional<const Foo, const Foo> o) { o.release_value(); }
+
+struct F {
+ F(const F&);
+ F(F&&) = delete;
+};
+
+struct Z {
+ Z(const Z&) = delete;
+ Z(Z&&) = delete;
+ Z(const Z&&);
+};
+
+const F& constfref();
+const Z& constzref();
+
+void
+g ()
+{
+ // Will call F::F(const F&) w/ and w/o std::move. So it's redundant.
+ F f = std::move (constfref()); // { dg-warning "redundant move in initialization" }
+ (void) f;
+ // Will call Z::Z(const Z&&) w/ std::move, and Z::Z(const Z&) w/o.
+ // So it's not redundant.
+ Z z = std::move (constzref());
+ (void) z;
+}
base-commit: e583c86f49b9ef6991b25308a0ad60de9697f24a
--
2.38.1
next reply other threads:[~2022-10-28 20:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-28 20:42 Marek Polacek [this message]
2022-11-07 14:07 ` Marek Polacek
2022-11-07 22:59 ` Jason Merrill
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221028204233.409310-1-polacek@redhat.com \
--to=polacek@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jason@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).