Re: [PATCH] evaluate: Allow sizeof(_Bool) to succeed.

[Christopher Li <sparse@chrisli.org>]

On Wed, May 4, 2011 at 4:39 PM, Ben Pfaff <blp@nicira.com> wrote:
> Without this commit, sizeof(_Bool) provokes an error with "cannot size
> expression" because _Bool is a 1-bit type and thus not a multiple of a full
> byte in size.  But sizeof(_Bool) is valid C that should evaluate to 1, so
> this commit fixes the problem and adds a regression test.

Thanks for the patch.

The sizeof _Bool is implementation define. Gcc make sizeof(_Bool) as 1.
I modify your patch to issue an warning. Applied and pushed.

The incremental change follows. Please check that works for you or not.

Chris

diff --git a/evaluate.c b/evaluate.c
index f196dbc..1309001 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -2028,14 +2028,18 @@ static struct symbol *evaluate_sizeof(struct
expression *expr)
 		size = bits_in_char;
 	}

+	if (size == 1 && is_bool_type(type)) {
+		warning(expr->pos, "expression using sizeof bool");
+		size = bits_in_char;
+	}
+
 	if (is_function(type->ctype.base_type)) {
 		warning(expr->pos, "expression using sizeof on a function");
 		size = bits_in_char;
 	}

-	if (is_bool_type(type))
-		size = bits_in_char;
-	else if ((size < 0) || (size & (bits_in_char - 1)))
+
+	if ((size < 0) || (size & (bits_in_char - 1)))
 		expression_error(expr, "cannot size expression");

 	expr->type = EXPR_VALUE;
diff --git a/validation/sizeof-bool.c b/validation/sizeof-bool.c
index dfcb12a..6c68748 100644
--- a/validation/sizeof-bool.c
+++ b/validation/sizeof-bool.c
@@ -6,4 +6,7 @@ static int a(void)
  * check-name: sizeof(_Bool) is valid
  * check-description: sizeof(_Bool) was rejected because _Bool is not an even
  * number of bytes
+ * check-error-start
+sizeof-bool.c:3:16: warning: expression using sizeof bool
+ * check-error-end
  */
--
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