On Fri, Dec 17, 2021 at 02:33:01PM -0500, Jason Merrill wrote:
> On 12/17/21 13:14, Marek Polacek wrote:
> > @@ -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)
>
> Rather than require multiple places to know about the magic -2, could we
> have an overload of attribute_ignored_p that takes an attribute_spec*? OK
> with that change.
Sure, here's what I'm pushing:
Tested x86_64-pc-linux-gnu, applying to 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 overloads.
* attribs.h (attribute_ignored_p): Declare them.
* 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 the attribute is ignored.
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 the attribute is ignored.
gcc/testsuite/ChangeLog:
* c-c++-common/Wno-attributes-6.c: New test.
---
gcc/attribs.c | 28 ++++++++++++++++++-
gcc/attribs.h | 2 ++
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, 56 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..9e7b7c1abd2 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 +569,32 @@ 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;
+}
+
+/* Like above, but takes an attribute_spec AS, which must be nonnull. */
+
+bool
+attribute_ignored_p (const attribute_spec *const as)
+{
+ return as->max_length == -2;
+}
+
/* 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..4928b126f59 100644
--- a/gcc/attribs.h
+++ b/gcc/attribs.h
@@ -39,6 +39,8 @@ 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 bool attribute_ignored_p (const attribute_spec *const);
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..b09ad307acd 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)
+ /* If this is a fake attribute created to handle -Wno-attributes,
+ we must skip parsing the arguments. */
+ if (as && !attribute_ignored_p (as))
{
bool takes_identifier
= (ns != NULL_TREE
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 44eed7ea638..33fb40a5b59 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)
+ /* If this is a fake attribute created to handle -Wno-attributes,
+ we must skip parsing the arguments. */
+ if (as == NULL || attribute_ignored_p (as))
{
if ((flag_openmp || flag_openmp_simd) && attr_ns == omp_identifier)
{
diff --git a/gcc/testsuite/c-c++-common/Wno-attributes-6.c
b/gcc/testsuite/c-c++-common/Wno-attributes-6.c
new file mode 100644
index 00000000000..ca3c7bebb99
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wno-attributes-6.c
@@ -0,0 +1,16 @@
+/* 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" } */
+/* { dg-additional-options "-Wno-attributes=vendor::assume" } */
+
+[[vendor::assume(1 + 1 == 2)]];
+[[foo::bar(1, 2)]];
+[[baz::bar(1, 2)]];
+[[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)))]];
diff --git a/gcc/tree-core.h b/gcc/tree-core.h
index 91ae5237d7e..9b37a065d18 100644
--- a/gcc/tree-core.h
+++ b/gcc/tree-core.h
@@ -2077,7 +2077,9 @@ struct attribute_spec {
/* The minimum length of the list of arguments of the attribute. */
int min_length;
/* The maximum length of the list of arguments of the attribute
- (-1 for no maximum). */
+ (-1 for no maximum). It can also be -2 for fake attributes
+ created for the sake of -Wno-attributes; in that case, we
+ should skip the balanced token sequence when parsing the attribute. */
int max_length;
/* Whether this attribute requires a DECL. If it does, it will be passed
from types of DECLs, function return types and array element types to
base-commit: d7ca2a79b82c6500ead6ab983d14c609e2124eee
--
2.33.1
