From 321983033d621e3f75e11d380c4463956a3f6e1e Mon Sep 17 00:00:00 2001 From: David Malcolm Date: Thu, 2 Jan 2025 15:10:15 -0500 Subject: c: special-case some "bool" errors with C23 (v2) [PR117629] Changed in v2: - distinguish between "bool" and "_Bool" when determining standard version This patch attempts to provide better error messages for code compiled with C23 that hasn't been updated for "bool", "true", and "false" becoming keywords. Specifically: (1) with "typedef int bool;" previously we emitted: t1.c:7:13: error: two or more data types in declaration specifiers 7 | typedef int bool; | ^~~~ t1.c:7:1: warning: useless type name in empty declaration 7 | typedef int bool; | ^~~~~~~ whereas with this patch we emit: t1.c:7:13: error: 'bool' cannot be defined via 'typedef' 7 | typedef int bool; | ^~~~ t1.c:7:13: note: 'bool' is a keyword with '-std=c23' onwards t1.c:7:1: warning: useless type name in empty declaration 7 | typedef int bool; | ^~~~~~~ (2) with "int bool;" previously we emitted: t2.c:7:5: error: two or more data types in declaration specifiers 7 | int bool; | ^~~~ t2.c:7:1: warning: useless type name in empty declaration 7 | int bool; | ^~~ whereas with this patch we emit: t2.c:7:5: error: 'bool' cannot be used here 7 | int bool; | ^~~~ t2.c:7:5: note: 'bool' is a keyword with '-std=c23' onwards t2.c:7:1: warning: useless type name in empty declaration 7 | int bool; | ^~~ (3) with "typedef enum { false = 0, true = 1 } _Bool;" previously we emitted: t3.c:7:16: error: expected identifier before 'false' 7 | typedef enum { false = 0, true = 1 } _Bool; | ^~~~~ t3.c:7:38: error: expected ';', identifier or '(' before '_Bool' 7 | typedef enum { false = 0, true = 1 } _Bool; | ^~~~~ t3.c:7:38: warning: useless type name in empty declaration whereas with this patch we emit: t3.c:7:16: error: cannot use keyword 'false' as enumeration constant 7 | typedef enum { false = 0, true = 1 } _Bool; | ^~~~~ t3.c:7:16: note: 'false' is a keyword with '-std=c23' onwards t3.c:7:38: error: expected ';', identifier or '(' before '_Bool' 7 | typedef enum { false = 0, true = 1 } _Bool; | ^~~~~ t3.c:7:38: warning: useless type name in empty declaration gcc/c/ChangeLog: PR c/117629 * c-decl.cc (declspecs_add_type): Special-case attempts to use bool as a typedef name or declaration name. * c-errors.cc (get_std_for_keyword): New. (add_note_about_new_keyword): New. * c-parser.cc (report_bad_enum_name): New, split out from... (c_parser_enum_specifier): ...here, adding handling for RID_FALSE and RID_TRUE. * c-tree.h (add_note_about_new_keyword): New decl. gcc/testsuite/ChangeLog: PR c/117629 * gcc.dg/auto-type-2.c: Update expected output with _Bool. * gcc.dg/c23-bool-errors-1.c: New test. * gcc.dg/c23-bool-errors-2.c: New test. * gcc.dg/c23-bool-errors-3.c: New test. Signed-off-by: David Malcolm --- gcc/c/c-parser.cc | 52 ++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 42 insertions(+), 10 deletions(-) (limited to 'gcc/c/c-parser.cc') diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc index d289af6..f72b0f0 100644 --- a/gcc/c/c-parser.cc +++ b/gcc/c/c-parser.cc @@ -3785,6 +3785,47 @@ c_parser_declspecs (c_parser *parser, struct c_declspecs *specs, specs->postfix_attrs = c_parser_std_attribute_specifier_sequence (parser); } +/* Complain about a non-CPP_NAME within an enumerator list. */ + +static void +report_bad_enum_name (c_parser *parser) +{ + if (!parser->error) + { + c_token *token = c_parser_peek_token (parser); + switch (token->type) + { + default: + break; + case CPP_CLOSE_BRACE: + /* Give a nicer error for "enum {}". */ + error_at (token->location, + "empty enum is invalid"); + parser->error = true; + return; + case CPP_KEYWORD: + /* Give a nicer error for attempts to use "true" and "false" + in enums with C23 onwards. */ + if (token->keyword == RID_FALSE + || token->keyword == RID_TRUE) + { + auto_diagnostic_group d; + error_at (token->location, + "cannot use keyword %qs as enumeration constant", + IDENTIFIER_POINTER (token->value)); + add_note_about_new_keyword (token->location, + token->value); + parser->error = true; + return; + } + break; + } + } + + /* Otherwise, a more generic error message. */ + c_parser_error (parser, "expected identifier"); +} + /* Parse an enum specifier (C90 6.5.2.2, C99 6.7.2.2, C11 6.7.2.2). enum-specifier: @@ -3952,16 +3993,7 @@ c_parser_enum_specifier (c_parser *parser) location_t decl_loc, value_loc; if (c_parser_next_token_is_not (parser, CPP_NAME)) { - /* Give a nicer error for "enum {}". */ - if (c_parser_next_token_is (parser, CPP_CLOSE_BRACE) - && !parser->error) - { - error_at (c_parser_peek_token (parser)->location, - "empty enum is invalid"); - parser->error = true; - } - else - c_parser_error (parser, "expected identifier"); + report_bad_enum_name (parser); c_parser_skip_until_found (parser, CPP_CLOSE_BRACE, NULL); values = error_mark_node; break; -- cgit v1.1