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author | Marek Polacek <polacek@redhat.com> | 2022-10-18 12:20:14 -0400 |
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committer | Marek Polacek <polacek@redhat.com> | 2022-10-19 15:27:56 -0400 |
commit | b3c98d6a59a6dcd5b0b52bd5676b586ef4fe785f (patch) | |
tree | 8f9a87dcd0a886370934e88cff686d89d84c7d23 /gcc/cp | |
parent | 79d38dd46e6b07e5a90ab25df1438eb0918eb475 (diff) | |
download | gcc-b3c98d6a59a6dcd5b0b52bd5676b586ef4fe785f.zip gcc-b3c98d6a59a6dcd5b0b52bd5676b586ef4fe785f.tar.gz gcc-b3c98d6a59a6dcd5b0b52bd5676b586ef4fe785f.tar.bz2 |
c++: Mitigate -Wuseless-cast with classes [PR85043]
-Wuseless-cast (not part of -Wall/-Wextra) warns here:
struct S { };
void g (S&&);
void f (S&& arg)
{
g (S(arg)); // warning: useless cast to type 'struct S'
}
which is wrong: the code will not compile without the cast because
"arg" is an lvalue which cannot bind to S&&.
This patch disables the warning when an object that isn't a prvalue
is cast to a non-reference type. Therefore we still warn about the
useless cast in "X(X{})".
PR c++/85043
gcc/cp/ChangeLog:
* typeck.cc (maybe_warn_about_useless_cast): Don't warn when
a glvalue is cast to a non-reference type.
gcc/ChangeLog:
* doc/invoke.texi: Update documentation of -Wuseless-cast.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wuseless-cast.C: Remove dg-warning.
* g++.dg/warn/Wuseless-cast3.C: New test.
Diffstat (limited to 'gcc/cp')
-rw-r--r-- | gcc/cp/typeck.cc | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc index da0e142..16e7d85 100644 --- a/gcc/cp/typeck.cc +++ b/gcc/cp/typeck.cc @@ -8104,11 +8104,13 @@ maybe_warn_about_useless_cast (location_t loc, tree type, tree expr, if (warn_useless_cast && complain & tf_warning) { - if ((TYPE_REF_P (type) - && (TYPE_REF_IS_RVALUE (type) - ? xvalue_p (expr) : lvalue_p (expr)) - && same_type_p (TREE_TYPE (expr), TREE_TYPE (type))) - || same_type_p (TREE_TYPE (expr), type)) + if (TYPE_REF_P (type) + ? ((TYPE_REF_IS_RVALUE (type) + ? xvalue_p (expr) : lvalue_p (expr)) + && same_type_p (TREE_TYPE (expr), TREE_TYPE (type))) + /* Don't warn when converting a class object to a non-reference type, + because that's a common way to create a temporary. */ + : (!glvalue_p (expr) && same_type_p (TREE_TYPE (expr), type))) warning_at (loc, OPT_Wuseless_cast, "useless cast to type %q#T", type); } |