[PATCH 43/73] c23: Add support for bool, true, and false keywords

[Bart Van Assche <bvanassche@acm.org>]

Register bool, true, and false as reserved keywords in C23 mode and
evaluate true and false as integer constant expressions of type bool
with values 1 and 0 in both C expressions and #if conditionals per ISO
C23 6.4.4.5 and 6.10.1.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 expression.c                | 15 ++++++++++++-
 ident-list.h                |  3 +++
 parse.c                     |  3 +++
 pre-process.c               | 10 +++++++++
 validation/c23-bool-error.c | 23 +++++++++++++++++++
 validation/c23-bool.c       | 45 +++++++++++++++++++++++++++++++++++++
 6 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 validation/c23-bool-error.c
 create mode 100644 validation/c23-bool.c

diff --git a/expression.c b/expression.c
index 4545adcf4c02..9b07963c914a 100644
--- a/expression.c
+++ b/expression.c
@@ -466,9 +466,22 @@ struct token *primary_expression(struct token *token, struct expression **tree)
 	}
 
 	case TOKEN_IDENT: {
-		struct symbol *sym = lookup_symbol(token->ident, NS_SYMBOL | NS_TYPEDEF);
+		struct symbol *sym;
 		struct token *next = token->next;
 
+		if (standard >= STANDARD_C23 &&
+		    (token->ident == &true_ident ||
+		     token->ident == &false_ident)) {
+			expr = alloc_expression(token->pos, EXPR_VALUE);
+			expr->flags = CEF_SET_INT;
+			expr->ctype = &bool_ctype;
+			expr->value = (token->ident == &true_ident);
+			token = next;
+			break;
+		}
+
+		sym = lookup_symbol(token->ident, NS_SYMBOL | NS_TYPEDEF);
+
 		if (!sym) {
 			sym = handle_func(token);
 			if (token->ident == &__builtin_types_compatible_p_ident) {
diff --git a/ident-list.h b/ident-list.h
index 83031b265388..31a37bede4ed 100644
--- a/ident-list.h
+++ b/ident-list.h
@@ -46,8 +46,11 @@ IDENT(_Thread_local);
 /* C23 keywords */
 IDENT(alignas);
 IDENT(alignof);
+IDENT(bool);
+IDENT(false);
 IDENT(static_assert);
 IDENT(thread_local);
+IDENT(true);
 
 /* Special case for L'\t' */
 IDENT(L);
diff --git a/parse.c b/parse.c
index d6c23fcdfb5d..4edfed1cdf97 100644
--- a/parse.c
+++ b/parse.c
@@ -520,6 +520,7 @@ static struct init_keyword {
 	N("unsigned",		&unsigned_op),
 	N("__int128",		&int128_op),
 	N("_Bool",		&spec_op,	.type = &bool_ctype),
+	N("bool",		&spec_op,	.type = &bool_ctype, .std = STANDARD_C23),
 
 	/* Predeclared types */
 	N("__builtin_va_list",	&spec_op,	.type = &ptr_ctype),
@@ -655,6 +656,8 @@ void init_parser_finalize(void)
 	if (standard >= STANDARD_C23) {
 		static_assert_ident.reserved = 1;
 		alignof_ident.reserved = 1;
+		true_ident.reserved = 1;
+		false_ident.reserved = 1;
 	}
 }
 
diff --git a/pre-process.c b/pre-process.c
index fbe4ba215532..a733927c4c14 100644
--- a/pre-process.c
+++ b/pre-process.c
@@ -1937,6 +1937,16 @@ static int expression_value(struct token **where)
 				continue;
 			if (token_type(p) != TOKEN_IDENT)
 				break;
+			if (standard >= STANDARD_C23 &&
+			    p->ident == &true_ident) {
+				replace_with_bool(p, 1);
+				break;
+			}
+			if (standard >= STANDARD_C23 &&
+			    p->ident == &false_ident) {
+				replace_with_bool(p, 0);
+				break;
+			}
 			token_type(p) = TOKEN_ZERO_IDENT;
 			break;
 		case 1:
diff --git a/validation/c23-bool-error.c b/validation/c23-bool-error.c
new file mode 100644
index 000000000000..49bfafa5bbd1
--- /dev/null
+++ b/validation/c23-bool-error.c
@@ -0,0 +1,23 @@
+static int (bool);
+static int (true);
+static int (false);
+typedef int bool;
+
+static void bad_lvalue(void)
+{
+	true = false;
+}
+
+/*
+ * check-name: c23-bool-error
+ * check-command: sparse -std=c23 -Wno-decl $file
+ *
+ * check-error-start
+c23-bool-error.c:1:12: error: Trying to use reserved word 'bool' as identifier
+c23-bool-error.c:2:12: error: Trying to use reserved word 'true' as identifier
+c23-bool-error.c:3:12: error: Trying to use reserved word 'false' as identifier
+c23-bool-error.c:4:13: error: two or more data types in declaration specifiers
+c23-bool-error.c:4:13: error: Trying to use reserved word 'bool' as identifier
+c23-bool-error.c:8:14: error: not an lvalue
+ * check-error-end
+ */
diff --git a/validation/c23-bool.c b/validation/c23-bool.c
new file mode 100644
index 000000000000..8b68b2ad9261
--- /dev/null
+++ b/validation/c23-bool.c
@@ -0,0 +1,45 @@
+#if true
+int t = 1;
+#endif
+
+#if !false
+int f = 1;
+#endif
+
+#if true + true != 2
+#error "true + true must equal 2 in preprocessor"
+#endif
+
+bool a = true;
+bool b = false;
+
+struct bool_bf {
+	bool flag : 1;
+};
+
+static_assert(true == 1, "true is 1");
+static_assert(false == 0, "false is 0");
+static_assert(true + true == 2, "integer promotion of true");
+static_assert(sizeof(true) == sizeof(bool), "sizeof true is sizeof bool");
+static_assert(sizeof(false) == sizeof(bool), "sizeof false is sizeof bool");
+static_assert(_Generic(true, bool: 1, int: 0, default: 0) == 1,
+	      "type of true is bool");
+static_assert(_Generic(false, bool: 1, int: 0, default: 0) == 1,
+	      "type of false is bool");
+static_assert(_Generic(+true, int: 1, bool: 0, default: 0) == 1,
+	      "+true promotes to int");
+
+static int test_conversions(void)
+{
+	bool b1 = (bool)0.5;
+	bool b2 = (bool)0.0;
+	bool b3 = (bool)&a;
+	struct bool_bf s = { .flag = true };
+
+	return b1 + !b2 + b3 + s.flag;
+}
+
+/*
+ * check-name: c23-bool
+ * check-command: sparse -std=c23 -pedantic -Wno-decl $file
+ */