Gentle ping on this simple patch.
thanks.
Qing
> On Aug 5, 2024, at 16:17, Qing Zhao <qing.z...@oracle.com> wrote:
>
> Compared to the first version, the major changes are:
>
> 1. Changed the error as a warning with -Wattributes per Jakub and Jason's
> comments.
> 2. Update documentation accordingly.
> 3. Move the testing case to g++.dg/ext
> Add one more new testing case for C++11
> Adjust the testing case according to the new warning.
>
> Bootstrapped and regression tested on both aarch64 and x86.
> Okay for committing?
>
> thanks.
>
> Qing.
>
> =================
>
> The "counted_by" attribute currently is only supported in C, mention this
> explicitly in documentation and also issue warnings when see "counted_by"
> attribute in C++ with -Wattributes.
>
> gcc/c-family/ChangeLog:
>
> * c-attribs.cc (handle_counted_by_attribute): Is ignored and issues
> warning with -Wattributes in C++ for now.
>
> gcc/ChangeLog:
>
> * doc/extend.texi: Explicitly mentions counted_by is available
> only in C for now.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/ext/flex-array-counted-by.C: New test.
> * g++.dg/ext/flex-array-counted-by-2.C: New test.
> ---
> gcc/c-family/c-attribs.cc | 10 +++++++++-
> gcc/doc/extend.texi | 3 +++
> gcc/testsuite/g++.dg/ext/flex-array-counted-by-2.C | 13 +++++++++++++
> gcc/testsuite/g++.dg/ext/flex-array-counted-by.C | 11 +++++++++++
> 4 files changed, 36 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/ext/flex-array-counted-by-2.C
> create mode 100644 gcc/testsuite/g++.dg/ext/flex-array-counted-by.C
>
> diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
> index 685f212683f..4f064457dc4 100644
> --- a/gcc/c-family/c-attribs.cc
> +++ b/gcc/c-family/c-attribs.cc
> @@ -2859,8 +2859,16 @@ handle_counted_by_attribute (tree *node, tree name,
> tree argval = TREE_VALUE (args);
> tree old_counted_by = lookup_attribute ("counted_by", DECL_ATTRIBUTES
> (decl));
>
> + /* This attribute is not supported in C++. */
> + if (c_dialect_cxx ())
> + {
> + warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wattributes,
> + "%qE attribute is not supported for C++ for now, ignored",
> + name);
> + *no_add_attrs = true;
> + }
> /* This attribute only applies to field decls of a structure. */
> - if (TREE_CODE (decl) != FIELD_DECL)
> + else if (TREE_CODE (decl) != FIELD_DECL)
> {
> error_at (DECL_SOURCE_LOCATION (decl),
> "%qE attribute is not allowed for a non-field"
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 48b27ff9f39..827044670e8 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -7848,6 +7848,9 @@ The @code{counted_by} attribute may be attached to the
> C99 flexible array
> member of a structure. It indicates that the number of the elements of the
> array is given by the field "@var{count}" in the same structure as the
> flexible array member.
> +This attribute is available only in C for now.
> +In C++, this attribute is ignored by default, and the compiler issues a
> +warning with @option{-Wattributes}.
> GCC may use this information to improve detection of object size information
> for such structures and provide better results in compile-time diagnostics
> and runtime features like the array bound sanitizer and
> diff --git a/gcc/testsuite/g++.dg/ext/flex-array-counted-by-2.C
> b/gcc/testsuite/g++.dg/ext/flex-array-counted-by-2.C
> new file mode 100644
> index 00000000000..6ac2b509b68
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/flex-array-counted-by-2.C
> @@ -0,0 +1,13 @@
> +/* Testing the fact that the attribute counted_by is not supported in C++.
> */
> +/* { dg-do compile { target c++11 } } */
> +/* { dg-options "-Wattributes" } */
> +
> +struct trailing {
> + int count;
> + int field [[gnu::counted_by (count)]] []; /* { dg-warning "attribute is
> not supported for C\\+\\+ for now, ignored" } */
> +};
> +
> +struct trailing1 {
> + int count1;
> + [[gnu::counted_by (count)]] int field []; /* { dg-warning "attribute is
> not supported for C\\+\\+ for now, ignored" } */
> +};
> diff --git a/gcc/testsuite/g++.dg/ext/flex-array-counted-by.C
> b/gcc/testsuite/g++.dg/ext/flex-array-counted-by.C
> new file mode 100644
> index 00000000000..8bc79d459df
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/flex-array-counted-by.C
> @@ -0,0 +1,11 @@
> +/* Testing the fact that the attribute counted_by is not supported in C++.
> */
> +/* { dg-do compile } */
> +/* { dg-options "-Wattributes" } */
> +
> +int size;
> +int x __attribute ((counted_by (size))); /* { dg-warning "attribute is not
> supported for C\\+\\+ for now, ignored" } */
> +
> +struct trailing {
> + int count;
> + int field[] __attribute ((counted_by (count))); /* { dg-warning "attribute
> is not supported for C\\+\\+ for now, ignored" } */
> +};
> --
> 2.31.1
>
