328 lines
12 KiB
Diff
328 lines
12 KiB
Diff
From 3714cfb47fafef884aa2ff330935fb44b7966909 Mon Sep 17 00:00:00 2001
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From: Richard Sandiford <richard.sandiford@arm.com>
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Date: Thu, 24 Aug 2023 11:49:58 +0100
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Subject: [PATCH 133/157] [Backport][SME] c: Add support for [[__extension__
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...]]
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Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=207a5daa9dcf31e367152163ad2a2ab4a0858967
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[[]] attributes are a recent addition to C, but as a GNU extension,
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GCC allows them to be used in C11 and earlier. Normally this use
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would trigger a pedwarn (for -pedantic, -Wc11-c2x-compat, etc.).
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This patch allows the pedwarn to be suppressed by starting the
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attribute-list with __extension__.
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Also, :: is not a single lexing token prior to C2X, so it wasn't
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possible to use scoped attributes in C11, even as a GNU extension.
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The patch allows two colons to be used in place of :: when
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__extension__ is used. No attempt is made to check whether the
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two colons are immediately adjacent.
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gcc/
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* doc/extend.texi: Document the C [[__extension__ ...]] construct.
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gcc/c/
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* c-parser.cc (c_parser_std_attribute): Conditionally allow
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two colons to be used in place of ::.
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(c_parser_std_attribute_list): New function, split out from...
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(c_parser_std_attribute_specifier): ...here. Allow the attribute-list
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to start with __extension__. When it does, also allow two colons
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to be used in place of ::.
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gcc/testsuite/
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* gcc.dg/c2x-attr-syntax-6.c: New test.
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* gcc.dg/c2x-attr-syntax-7.c: Likewise.
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---
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gcc/c/c-parser.cc | 64 ++++++++++++++++++------
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gcc/doc/extend.texi | 27 ++++++++--
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gcc/testsuite/gcc.dg/c2x-attr-syntax-6.c | 62 +++++++++++++++++++++++
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gcc/testsuite/gcc.dg/c2x-attr-syntax-7.c | 60 ++++++++++++++++++++++
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4 files changed, 193 insertions(+), 20 deletions(-)
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create mode 100644 gcc/testsuite/gcc.dg/c2x-attr-syntax-6.c
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create mode 100644 gcc/testsuite/gcc.dg/c2x-attr-syntax-7.c
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diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
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index 78a313fe3..486f46e1c 100644
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--- a/gcc/c/c-parser.cc
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+++ b/gcc/c/c-parser.cc
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@@ -4894,10 +4894,18 @@ c_parser_balanced_token_sequence (c_parser *parser)
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( balanced-token-sequence[opt] )
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Keywords are accepted as identifiers for this purpose.
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-*/
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+
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+ As an extension, we permit an attribute-specifier to be:
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+
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+ [ [ __extension__ attribute-list ] ]
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+
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+ Two colons are then accepted as a synonym for ::. No attempt is made
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+ to check whether the colons are immediately adjacent. LOOSE_SCOPE_P
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+ indicates whether this relaxation is in effect. */
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static tree
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-c_parser_std_attribute (c_parser *parser, bool for_tm)
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+c_parser_std_attribute (c_parser *parser, bool for_tm,
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+ bool loose_scope_p = false)
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{
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c_token *token = c_parser_peek_token (parser);
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tree ns, name, attribute;
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@@ -4910,9 +4918,14 @@ c_parser_std_attribute (c_parser *parser, bool for_tm)
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}
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name = canonicalize_attr_name (token->value);
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c_parser_consume_token (parser);
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- if (c_parser_next_token_is (parser, CPP_SCOPE))
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+ if (c_parser_next_token_is (parser, CPP_SCOPE)
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+ || (loose_scope_p
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+ && c_parser_next_token_is (parser, CPP_COLON)
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+ && c_parser_peek_2nd_token (parser)->type == CPP_COLON))
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{
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ns = name;
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+ if (c_parser_next_token_is (parser, CPP_COLON))
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+ c_parser_consume_token (parser);
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c_parser_consume_token (parser);
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token = c_parser_peek_token (parser);
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if (token->type != CPP_NAME && token->type != CPP_KEYWORD)
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@@ -4981,19 +4994,9 @@ c_parser_std_attribute (c_parser *parser, bool for_tm)
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}
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static tree
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-c_parser_std_attribute_specifier (c_parser *parser, bool for_tm)
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+c_parser_std_attribute_list (c_parser *parser, bool for_tm,
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+ bool loose_scope_p = false)
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{
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- location_t loc = c_parser_peek_token (parser)->location;
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- if (!c_parser_require (parser, CPP_OPEN_SQUARE, "expected %<[%>"))
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- return NULL_TREE;
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- if (!c_parser_require (parser, CPP_OPEN_SQUARE, "expected %<[%>"))
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- {
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- c_parser_skip_until_found (parser, CPP_CLOSE_SQUARE, "expected %<]%>");
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- return NULL_TREE;
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- }
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- if (!for_tm)
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- pedwarn_c11 (loc, OPT_Wpedantic,
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- "ISO C does not support %<[[]]%> attributes before C2X");
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tree attributes = NULL_TREE;
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while (true)
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{
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@@ -5005,7 +5008,7 @@ c_parser_std_attribute_specifier (c_parser *parser, bool for_tm)
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c_parser_consume_token (parser);
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continue;
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}
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- tree attribute = c_parser_std_attribute (parser, for_tm);
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+ tree attribute = c_parser_std_attribute (parser, for_tm, loose_scope_p);
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if (attribute != error_mark_node)
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{
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TREE_CHAIN (attribute) = attributes;
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@@ -5014,6 +5017,35 @@ c_parser_std_attribute_specifier (c_parser *parser, bool for_tm)
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if (c_parser_next_token_is_not (parser, CPP_COMMA))
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break;
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}
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+ return attributes;
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+}
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+
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+static tree
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+c_parser_std_attribute_specifier (c_parser *parser, bool for_tm)
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+{
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+ location_t loc = c_parser_peek_token (parser)->location;
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+ if (!c_parser_require (parser, CPP_OPEN_SQUARE, "expected %<[%>"))
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+ return NULL_TREE;
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+ if (!c_parser_require (parser, CPP_OPEN_SQUARE, "expected %<[%>"))
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+ {
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+ c_parser_skip_until_found (parser, CPP_CLOSE_SQUARE, "expected %<]%>");
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+ return NULL_TREE;
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+ }
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+ tree attributes;
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+ if (c_parser_next_token_is_keyword (parser, RID_EXTENSION))
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+ {
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+ auto ext = disable_extension_diagnostics ();
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+ c_parser_consume_token (parser);
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+ attributes = c_parser_std_attribute_list (parser, for_tm, true);
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+ restore_extension_diagnostics (ext);
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+ }
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+ else
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+ {
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+ if (!for_tm)
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+ pedwarn_c11 (loc, OPT_Wpedantic,
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+ "ISO C does not support %<[[]]%> attributes before C2X");
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+ attributes = c_parser_std_attribute_list (parser, for_tm);
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+ }
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c_parser_skip_until_found (parser, CPP_CLOSE_SQUARE, "expected %<]%>");
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c_parser_skip_until_found (parser, CPP_CLOSE_SQUARE, "expected %<]%>");
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return nreverse (attributes);
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diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
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index 674db2f1a..3cfecee53 100644
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--- a/gcc/doc/extend.texi
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+++ b/gcc/doc/extend.texi
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@@ -11726,10 +11726,29 @@ macros to replace them with the customary keywords. It looks like this:
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@findex __extension__
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@opindex pedantic
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@option{-pedantic} and other options cause warnings for many GNU C extensions.
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-You can
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-prevent such warnings within one expression by writing
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-@code{__extension__} before the expression. @code{__extension__} has no
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-effect aside from this.
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+You can suppress such warnings using the keyword @code{__extension__}.
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+Specifically:
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+
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+@itemize @bullet
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+@item
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+Writing @code{__extension__} before an expression prevents warnings
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+about extensions within that expression.
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+
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+@item
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+In C, writing:
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+
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+@smallexample
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+[[__extension__ @dots{}]]
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+@end smallexample
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+
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+suppresses warnings about using @samp{[[]]} attributes in C versions
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+that predate C2X@. Since the scope token @samp{::} is not a single
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+lexing token in earlier versions of C, this construct also allows two colons
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+to be used in place of @code{::}. GCC does not check whether the two
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+colons are immediately adjacent.
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+@end itemize
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+
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+@code{__extension__} has no effect aside from this.
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@node Incomplete Enums
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@section Incomplete @code{enum} Types
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diff --git a/gcc/testsuite/gcc.dg/c2x-attr-syntax-6.c b/gcc/testsuite/gcc.dg/c2x-attr-syntax-6.c
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new file mode 100644
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index 000000000..9e5f65ce4
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--- /dev/null
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+++ b/gcc/testsuite/gcc.dg/c2x-attr-syntax-6.c
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@@ -0,0 +1,62 @@
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+/* Test C2x attribute syntax: use of __extension__ in C11 mode. */
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+/* { dg-do compile } */
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+/* { dg-options "-std=c11 -pedantic-errors" } */
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+
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+#define FOO ::
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+#define BAR :
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+#define JOIN(A, B) A/**/B
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+#define JOIN2(A, B) A##B
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+
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+typedef int [[__extension__ gnu::vector_size (4)]] g1;
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+typedef int [[__extension__ gnu :: vector_size (4)]] g2;
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+typedef int [[__extension__ gnu : : vector_size (4)]] g3;
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+typedef int [[__extension__ gnu: :vector_size (4)]] g4;
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+typedef int [[__extension__ gnu FOO vector_size (4)]] g5;
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+typedef int [[__extension__ gnu BAR BAR vector_size (4)]] g6;
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+typedef int [[__extension__ gnu :/**/: vector_size (4)]] g7;
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+typedef int [[__extension__ gnu JOIN(:,:) vector_size (4)]] g8;
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+typedef int [[__extension__ gnu :: vector_size (sizeof (void (*)(...)))]] g10;
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+typedef int [[__extension__]] g11;
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+typedef int [[__extension__,]] g12;
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+typedef int [[__extension__, ,,,, ,, ,]] g13;
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+[[__extension__ deprecated]] int g14 ();
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+[[__extension__ nodiscard]] int g15 ();
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+[[__extension__ noreturn]] void g16 ();
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+
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+int
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+cases (int x)
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+{
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+ switch (x)
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+ {
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+ case 1:
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+ case 2:
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+ case 4:
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+ x += 1;
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+ [[__extension__ fallthrough]];
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+ case 19:
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+ case 33:
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+ x *= 2;
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+ [[fallthrough]]; /* { dg-error {attributes before C2X} } */
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+ case 99:
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+ return x;
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+
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+ default:
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+ return 0;
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+ }
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+}
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+
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+typedef int [[__extension__ vector_size (4)]] b1; /* { dg-error {'vector_size' attribute ignored} } */
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+typedef int [[__extension__ __extension__]] b2; /* { dg-error {'extension' attribute ignored} } */
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+typedef int [[__extension__ unknown_attribute]] b3; /* { dg-error {'unknown_attribute' attribute ignored} } */
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+typedef int [[__extension__ gnu:vector_size(4)]] b4; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+typedef int [[__extension__ gnu JOIN2(:,:) vector_size (4)]] b5; /* { dg-error {pasting ":" and ":" does not give a valid preprocessing token} } */
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+typedef int [[gnu::vector_size(4)]] b6; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+/* { dg-error {attributes before C2X} "" { target *-*-* } .-2 } */
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+typedef int [[gnu : : vector_size(4)]] b7; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+/* { dg-error {attributes before C2X} "" { target *-*-* } .-2 } */
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+typedef int [[gnu : vector_size(4)]] b8; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+/* { dg-error {attributes before C2X} "" { target *-*-* } .-2 } */
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diff --git a/gcc/testsuite/gcc.dg/c2x-attr-syntax-7.c b/gcc/testsuite/gcc.dg/c2x-attr-syntax-7.c
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new file mode 100644
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index 000000000..702f733b1
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--- /dev/null
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+++ b/gcc/testsuite/gcc.dg/c2x-attr-syntax-7.c
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@@ -0,0 +1,60 @@
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+/* Test C2x attribute syntax: use of __extension__ in C11 mode. */
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+/* { dg-do compile } */
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+/* { dg-options "-std=c2x -pedantic-errors -Wc11-c2x-compat" } */
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+
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+#define FOO ::
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+#define BAR :
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+#define JOIN(A, B) A/**/B
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+#define JOIN2(A, B) A##B
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+
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+typedef int [[__extension__ gnu::vector_size (4)]] g1;
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+typedef int [[__extension__ gnu :: vector_size (4)]] g2;
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+typedef int [[__extension__ gnu : : vector_size (4)]] g3;
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+typedef int [[__extension__ gnu: :vector_size (4)]] g4;
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+typedef int [[__extension__ gnu FOO vector_size (4)]] g5;
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+typedef int [[__extension__ gnu BAR BAR vector_size (4)]] g6;
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+typedef int [[__extension__ gnu :/**/: vector_size (4)]] g7;
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+typedef int [[__extension__ gnu JOIN(:,:) vector_size (4)]] g8;
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+typedef int [[__extension__ gnu :: vector_size (sizeof (void (*)(...)))]] g10;
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+typedef int [[__extension__]] g11;
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+typedef int [[__extension__,]] g12;
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+typedef int [[__extension__, ,,,, ,, ,]] g13;
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+[[__extension__ deprecated]] int g14 ();
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+[[__extension__ nodiscard]] int g15 ();
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+[[__extension__ noreturn]] void g16 ();
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+
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+int
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+cases (int x)
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+{
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+ switch (x)
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+ {
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+ case 1:
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+ case 2:
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+ case 4:
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+ x += 1;
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+ [[__extension__ fallthrough]];
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+ case 19:
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+ case 33:
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+ x *= 2;
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+ [[fallthrough]]; /* { dg-warning {attributes before C2X} } */
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+ case 99:
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+ return x;
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+
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+ default:
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+ return 0;
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+ }
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+}
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+
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+typedef int [[__extension__ vector_size (4)]] b1; /* { dg-error {'vector_size' attribute ignored} } */
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+typedef int [[__extension__ __extension__]] b2; /* { dg-error {'extension' attribute ignored} } */
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+typedef int [[__extension__ unknown_attribute]] b3; /* { dg-error {'unknown_attribute' attribute ignored} } */
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+typedef int [[__extension__ gnu:vector_size(4)]] b4; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+typedef int [[__extension__ gnu JOIN2(:,:) vector_size (4)]] b5;
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+typedef int [[gnu::vector_size(4)]] b6; /* { dg-warning {attributes before C2X} } */
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+typedef int [[gnu : : vector_size(4)]] b7; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+/* { dg-warning {attributes before C2X} "" { target *-*-* } .-2 } */
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+typedef int [[gnu : vector_size(4)]] b8; /* { dg-error {expected '\]' before ':'} } */
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+/* { dg-error {'gnu' attribute ignored} "" { target *-*-* } .-1 } */
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+/* { dg-warning {attributes before C2X} "" { target *-*-* } .-2 } */
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--
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2.33.0
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