The C++17 standard (and C2x) says that [[maybe_unused]] may be applied to a
non-static data member, so we shouldn't warn about it. And I don't see a
reason not to handle a FIELD_DECL the same as any other decl, by setting
TREE_USED on it. It doesn't look like anything yet cares about that flag on a
FIELD_DECL, but setting it shouldn't hurt.
Tested x86_64-pc-linux-gnu, applying to trunk.
gcc/c-family/ChangeLog:
* c-attribs.c (handle_unused_attribute): Handle FIELD_DECL.
gcc/testsuite/ChangeLog:
* g++.dg/ext/attrib62.C: No longer warn.
* g++.dg/diagnostic/maybe_unused1.C: New test.
---
gcc/doc/extend.texi | 6 +++---
gcc/c-family/c-attribs.c | 1 +
gcc/testsuite/g++.dg/diagnostic/maybe_unused1.C | 17 +++++++++++++++++
gcc/testsuite/g++.dg/ext/attrib62.C | 2 +-
4 files changed, 22 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/diagnostic/maybe_unused1.C
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 408979b78af..8fc66d626d8 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -7516,9 +7516,9 @@ Not all targets support this attribute.
@item unused
@cindex @code{unused} variable attribute
-This attribute, attached to a variable, means that the variable is meant
-to be possibly unused. GCC does not produce a warning for this
-variable.
+This attribute, attached to a variable or structure field, means that
+the variable or field is meant to be possibly unused. GCC does not
+produce a warning for this variable or field.
@item used
@cindex @code{used} variable attribute
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 42026a811dd..6bf492afcc0 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -1568,6 +1568,7 @@ handle_unused_attribute (tree *node, tree name, tree
ARG_UNUSED (args),
|| VAR_OR_FUNCTION_DECL_P (decl)
|| TREE_CODE (decl) == LABEL_DECL
|| TREE_CODE (decl) == CONST_DECL
+ || TREE_CODE (decl) == FIELD_DECL
|| TREE_CODE (decl) == TYPE_DECL)
{
TREE_USED (decl) = 1;
diff --git a/gcc/testsuite/g++.dg/diagnostic/maybe_unused1.C
b/gcc/testsuite/g++.dg/diagnostic/maybe_unused1.C
new file mode 100644
index 00000000000..70a8ec937dd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/maybe_unused1.C
@@ -0,0 +1,17 @@
+/* [dcl.attr.unused] The attribute may be applied to the declaration of a
+ class, a typedef-name, a variable (including a structured binding
+ declaration), a non-static data member, a function, an enumeration, or an
+ enumerator. */
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-Wunused -Wextra" }
+
+class [[maybe_unused]] Test {
+ [[maybe_unused]] int a_;
+ void b() {};
+};
+
+[[maybe_unused]] typedef Test Test2;
+
+[[maybe_unused]] int i;
+[[maybe_unused]] void f();
+enum [[maybe_unused]] E { e [[maybe_unused]] = 42 };
diff --git a/gcc/testsuite/g++.dg/ext/attrib62.C
b/gcc/testsuite/g++.dg/ext/attrib62.C
index 116ee829a2d..d34cd2549de 100644
--- a/gcc/testsuite/g++.dg/ext/attrib62.C
+++ b/gcc/testsuite/g++.dg/ext/attrib62.C
@@ -3,5 +3,5 @@
template<typename T> struct A
{
- T a, __attribute((unused)) b; // { dg-warning "attribute ignored" }
+ T a, __attribute((unused)) b;
};
base-commit: 08e1ff9d6e5a419d5b4a60c077df549e81601d9b
--
2.27.0
