On Thu, Dec 16, 2021 at 08:06:43PM -0500, Jason Merrill wrote:
On 12/16/21 19:52, Marek Polacek wrote:
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wno-attributes-6.c
@@ -0,0 +1,14 @@
+/* PR c/103649 */
+/* { dg-do compile { target { c || c++11 } } } */
+/* { dg-additional-options "-Wno-attributes=foo::bar" } */
+/* { dg-additional-options "-Wno-attributes=baz::" } */
+/* { dg-additional-options "-Wno-attributes=womp::womp" } */
+/* { dg-additional-options "-Wno-attributes=qux::foo" } */
+
+[[foo::bar(1, 2)]]; /* { dg-warning "attribute ignored" } */
+[[baz::bar(1, 2)]]; /* { dg-warning "attribute ignored" } */
+[[foo::bar(1, 2)]] void f1();
+[[baz::bar(1, 2)]] void f2();
+[[qux::foo({t})]] void f3();
+[[womp::womp (another::directive (threadprivate (t)))]] void f4();
+[[womp::womp (another::directive (threadprivate (t)))]]; /* { dg-warning "attribute
ignored" } */
If we're ignoring these attributes, we should ignore them everywhere;
perhaps using them for an attribute-declaration is meaningful in another
compiler.
Sounds good. Reminds me of P177, Portable assumptions...
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
My patch to implement -Wno-attribute=A::b caused a bogus error when
parsing
[[foo::bar(1, 2)]];
when -Wno-attributes=foo::bar was specified on the command line, because
when we create a fake foo::bar attribute and insert it into our attribute
table, it is created with max_length == 0 which doesn't allow any args.
That is wrong -- we know nothing about the attribute, so we shouldn't
require any specific number of arguments. And since unknown attributes
can be rather complex (see for example omp::{directive,sequence}), we
must skip parsing their arguments. To that end, I'm using max_length
with value -2.
Also let's not warn about things like
[[vendor::assume(true)]];
because they may have some meaning (this is reminiscent of C++ Portable
Assumptions).
PR c/103649
gcc/ChangeLog:
* attribs.c (handle_ignored_attributes_option): Create the fake
attribute with max_length == -2.
(attribute_ignored_p): New function.
* attribs.h (attribute_ignored_p): Declare.
* tree-core.h (struct attribute_spec): Document that max_length
can be -2.
gcc/c/ChangeLog:
* c-decl.c (c_warn_unused_attributes): Don't warn for
attribute_ignored_p.
* c-parser.c (c_parser_std_attribute): Skip parsing of the attribute
arguments when max_length == -2.
gcc/cp/ChangeLog:
* parser.c (cp_parser_declaration): Don't warn for attribute_ignored_p.
(cp_parser_std_attribute): Skip parsing of the attribute
arguments when max_length == -2.
gcc/testsuite/ChangeLog:
* c-c++-common/Wno-attributes-6.c: New test.
---
gcc/attribs.c | 20 ++++++++++++++++++-
gcc/attribs.h | 1 +
gcc/c/c-decl.c | 2 +-
gcc/c/c-parser.c | 4 +++-
gcc/cp/parser.c | 6 ++++--
gcc/testsuite/c-c++-common/Wno-attributes-6.c | 16 +++++++++++++++
gcc/tree-core.h | 4 +++-
7 files changed, 47 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/Wno-attributes-6.c
diff --git a/gcc/attribs.c b/gcc/attribs.c
index 29703e75fba..82527869093 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -304,7 +304,7 @@ handle_ignored_attributes_option (vec<char *> *v)
We can't free it here, so squirrel away the pointers. */
attribute_spec *table = new attribute_spec[2];
ignored_attributes_table.safe_push (table);
- table[0] = { attr, 0, 0, false, false, false, false, nullptr, nullptr };
+ table[0] = { attr, 0, -2, false, false, false, false, nullptr, nullptr };
table[1] = { nullptr, 0, 0, false, false, false, false, nullptr,
nullptr };
register_scoped_attributes (table, IDENTIFIER_POINTER (vendor_id),
!attr);
@@ -569,6 +569,24 @@ attr_namespace_ignored_p (tree ns)
return r && r->ignored_p;
}
+/* Return true if the attribute ATTR should not be warned about. */
+
+bool
+attribute_ignored_p (tree attr)
+{
+ if (!cxx11_attribute_p (attr))
+ return false;
+ if (tree ns = get_attribute_namespace (attr))
+ {
+ if (attr_namespace_ignored_p (ns))
+ return true;
+ const attribute_spec *as = lookup_attribute_spec (TREE_PURPOSE (attr));
+ if (as && as->max_length == -2)
+ return true;
+ }
+ return false;
+}
+
/* Process the attributes listed in ATTRIBUTES and install them in *NODE,
which is either a DECL (including a TYPE_DECL) or a TYPE. If a DECL,
it should be modified in place; if a TYPE, a copy should be created
diff --git a/gcc/attribs.h b/gcc/attribs.h
index f5899d83c0b..d3449d5bd1d 100644
--- a/gcc/attribs.h
+++ b/gcc/attribs.h
@@ -39,6 +39,7 @@ extern tree get_attribute_name (const_tree);
extern tree get_attribute_namespace (const_tree);
extern void apply_tm_attr (tree, tree);
extern tree make_attribute (const char *, const char *, tree);
+extern bool attribute_ignored_p (tree);
extern struct scoped_attributes* register_scoped_attributes (const struct attribute_spec *,
const char *,
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 4b5481ce8f4..516e3c26e21 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4643,7 +4643,7 @@ c_warn_unused_attributes (tree attrs)
constraint violation. */
pedwarn (input_location, OPT_Wattributes, "%qE attribute ignored",
get_attribute_name (t));
- else
+ else if (!attribute_ignored_p (t))
warning (OPT_Wattributes, "%qE attribute ignored",
get_attribute_name (t));
}
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index d7e5f051ac0..c9068bdbb8a 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -4943,7 +4943,9 @@ c_parser_std_attribute (c_parser *parser, bool for_tm)
parens.skip_until_found_close (parser);
return error_mark_node;
}
- if (as)
+ /* When MAX_LENGTH is -2, this is a fake attribute created to
+ handle -Wno-attributes, and we must skip parsing the arguments. */
+ if (as && as->max_length != -2)
{
bool takes_identifier
= (ns != NULL_TREE
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 44eed7ea638..a843c953da8 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -14776,7 +14776,7 @@ cp_parser_declaration (cp_parser* parser, tree
prefix_attrs)
}
}
- if (std_attrs != NULL_TREE)
+ if (std_attrs != NULL_TREE && !attribute_ignored_p (std_attrs))
warning_at (make_location (attrs_loc, attrs_loc, parser->lexer),
OPT_Wattributes, "attribute ignored");
if (cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON))
@@ -28979,7 +28979,9 @@ cp_parser_std_attribute (cp_parser *parser, tree
attr_ns)
/* A GNU attribute that takes an identifier in parameter. */
attr_flag = id_attr;
- if (as == NULL)
+ /* When MAX_LENGTH is -2, this is a fake attribute created to
+ handle -Wno-attributes, and we must skip parsing the arguments. */
+ if (as == NULL || as->max_length == -2)