From 6afb8a68a9113897ccf39e40983e042ed90d7aed Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Thu, 16 Dec 2021 16:29:41 -0500 Subject: [PATCH] attribs: Fix wrong error with -Wno-attribute=A::b [PR103649] 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 *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 -- 2.11.4.GIT