On Wed, Jan 06, 2016 at 01:35:17PM -0500, Lance Richardson wrote:
> This patch introduces support for _Static_assert() in global,
> function, and struct/union declaration contexts (as currently supported
> by gcc).
>
> Tested via:
> - kernel build with C=1 CF=-D__CHECK_ENDIAN__
> - build/check large code base making heavy use of _Static_assert()
> - "make check" with added test case for static assert support
Nice, it was something that was indeed missing.
I have a few remarks, mostly nitpicking, here under.
Luc
> @@ -437,6 +443,10 @@ static struct init_keyword {
> { "__restrict", NS_TYPEDEF, .op = &restrict_op},
> { "__restrict__", NS_TYPEDEF, .op = &restrict_op},
>
> +
> + /* Static assertion */
> + { "_Static_assert", NS_TYPEDEF, .op = &static_assert_op },
> +
It seems a bit strange to me to use NS_TYPEDEF, as this is unrelated types.
OTOH, the other namespaces deosn't seems better suited,
and yes C11 define this as sort of declaration, so ...
> @@ -2004,6 +2014,27 @@ static struct token *parse_asm_declarator(struct token *token, struct decl_state
> return token;
> }
>
> +
> +static struct token *static_assert_specifier(struct token *token, struct decl_state *ctx)
> +{
> + struct expression *expr = NULL;
> + int val;
> +
> + token = constant_expression(token->next, &expr);
> + if (!expr)
> + sparse_error(token->pos, "Expected constant expression");
> + val = get_expression_value(expr);
> + token = expect(token, ',', "after first argument of _Static_assert");
> + token = parse_expression(token, &expr);
> + token = expect(token, ')', "after second argument of _Static_assert");
> +
> + if (!val)
> + sparse_error(token->pos, "static assertion failed: %s",
> + show_string(expr->string));
By using token->pos here, the error message will indicate that the problem is
situated at the very end of the assertion; more exactly, at the ending ";".
This is a little annoying I find.
It would be better to use the some position as the expression
(expr->pos, or the same as for "Expected constant expression").
I find also a bit strange to have this sort of semantic check inside the parser.
> diff --git a/validation/static_assert.c b/validation/static_assert.c
> new file mode 100644
> index 0000000..baab346
> --- /dev/null
> +++ b/validation/static_assert.c
> @@ -0,0 +1,20 @@
> +_Static_assert(1, "global ok");
> +
> +struct foo {
> + _Static_assert(1, "struct ok");
> +};
> +
> +void bar(void)
> +{
> + _Static_assert(1, " func ok");
> +}
> +
> +_Static_assert(0, "expected failure");
> +/*
> + * check-name: static assertion
> + *
> + * check-error-start
> +static_assert.c:12:38: error: static assertion failed: "expected failure"
> + * check-error-end
> + */
It would be nice to add a few more test cases,
I'm thinbking to things like:
static int f;
_Static_assert(f, "non-constant expression");
static int *p;
_Static_assert(p, "non-integer expression");
_Static_assert(0.1, "float expression");
_Static_assert(!0 == 1, "non-trivial expression");
static int array[4];
_Static_assert(sizeof(array), "sizeof expression");
static const char non_literal_string[] = "non literal string";
_Static_assert(0, non_literal_string);
Also, what should happen with:
_Static_assert(1 / 0, "invalid expression: should not show up?");
(The C11 standard is not clear to me, GCC outputs an "invalid expression"
message and ignore the assertion).
Finally, the standard also allow to place the assertion
inside a struct or union declaration; like:
struct s {
char c;
_Static_assert(1, "inside struct");
};
which is working fine.
And also, I think:
struct s2 {
char c;
_Static_assert(sizeof(struct s) == 1, "own struct sizeof");
};
which doesn't.
Yours,
Luc
--
To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
