From 6b927b1297e66e26e62e722bf15c921dcbbd25b9 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Tue, 2 May 2023 15:48:40 -0400
Subject: [PATCH] c++: Move -Wdangling-reference to -Wextra [PR109642]
Sadly, -Wdangling-reference generates false positives for std::span-like
user classes, and it seems imprudent to attempt to improve the heuristic
in GCC 13. Let's move the warning to -Wextra, that will hopefully
reduce the number of false positives the users have been seeing with 13.
I'm leaving the warning in -Wall in 14 where I think I can write code
to detect std::span-like classes.
PR c++/109642
PR c++/109640
PR c++/109671
gcc/c-family/ChangeLog:
* c.opt (Wdangling-reference): Move from -Wall to -Wextra.
gcc/ChangeLog:
* doc/invoke.texi: Document that -Wdangling-reference is
enabled by -Wextra.
---
gcc/c-family/c.opt | 2 +-
gcc/doc/invoke.texi | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 3333cddeece7..a75038930aef 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -560,7 +560,7 @@ C ObjC C++ ObjC++ Joined RejectNegative UInteger Var(warn_dangling_pointer) Warn
Warn for uses of pointers to auto variables whose lifetime has ended.
Wdangling-reference
-C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wall)
+C++ ObjC++ Var(warn_dangling_reference) Warning LangEnabledBy(C++ ObjC++, Wextra)
Warn when a reference is bound to a temporary whose lifetime has ended.
Wdate-time
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a38547f53e53..36ed15914409 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -3781,7 +3781,7 @@ where @code{std::minmax} returns @code{std::pair<const int&, const int&>}, and
both references dangle after the end of the full expression that contains
the call to @code{std::minmax}.
-This warning is enabled by @option{-Wall}.
+This warning is enabled by @option{-Wextra}.
@opindex Wdelete-non-virtual-dtor
@opindex Wno-delete-non-virtual-dtor
@@ -6126,6 +6126,7 @@ name is still supported, but the newer name is more descriptive.)
@gccoptlist{-Wclobbered
-Wcast-function-type
+-Wdangling-reference @r{(C++ only)}
-Wdeprecated-copy @r{(C++ only)}
-Wempty-body
-Wenum-conversion @r{(C only)}
--
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