As discussed in PR116016:https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116016#c48
We should explicitly document this limitation and issue error messages for C++.
The "counted_by" attribute currently is only supported in C, mention this
explicitly in documentation and also issue error when see "counted_by"
attribute in C++.
The patch has been bootstrappped and regression tested on both aarch64 and X86,
no issue.
Okay for committing?
thanks.
Qing
gcc/c-family/ChangeLog:
* c-attribs.cc (handle_counted_by_attribute): Issue error for C++.
gcc/ChangeLog:
* doc/extend.texi: Explicitly mentions counted_by is available
only for C.
gcc/testsuite/ChangeLog:
* g++.dg/flex-array-counted-by.C: New test.
---
gcc/c-family/c-attribs.cc | 9 ++++++++-
gcc/doc/extend.texi | 1 +
gcc/testsuite/g++.dg/flex-array-counted-by.C | 11 +++++++++++
3 files changed, 20 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/flex-array-counted-by.C
diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index 685f212683f..f936058800b 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -2859,8 +2859,15 @@ 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 ())
+ {
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qE attribute is not supported for C++", 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..f31f3bdb53d 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -7848,6 +7848,7 @@ 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 for C.
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/flex-array-counted-by.C
b/gcc/testsuite/g++.dg/flex-array-counted-by.C
new file mode 100644
index 00000000000..7f1a345615e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/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 "-O2" } */
+
+int size;
+int x __attribute ((counted_by (size))); /* { dg-error "attribute is not
supported for C\\+\\+" } */
+
+struct trailing {
+ int count;
+ int field[] __attribute ((counted_by (count))); /* { dg-error "attribute is
not supported for C\\+\\+" } */
+};
--
2.31.1
