From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolai Stange Subject: [PATCH v2 09/13] expression: examine constness of __builtin_offsetof at evaluation only Date: Mon, 25 Jan 2016 16:00:48 +0100 Message-ID: <87r3h5eman.fsf@gmail.com> References: <87twm1g1go.fsf@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:36332 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751092AbcAYPAv (ORCPT ); Mon, 25 Jan 2016 10:00:51 -0500 Received: by mail-wm0-f66.google.com with SMTP id l65so11783216wmf.3 for ; Mon, 25 Jan 2016 07:00:50 -0800 (PST) In-Reply-To: <87twm1g1go.fsf@gmail.com> (Nicolai Stange's message of "Mon, 25 Jan 2016 15:47:51 +0100") Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: linux-sparse@vger.kernel.org Cc: Nicolai Stange , Christopher Li , Josh Triplett , Luc Van Oostenryck Currently, the determination of a __builtin_offsetof() expressions' constness flags is done in two steps: - Several flags are speculatively set at expression parsing time - and possibly cleared again at evaluation if the member expression includes a non-const array index like in __builtin_offsetof(struct A, a.b[non_const_foo]) For consistency with other expression types' evaluation, defer the determination of a __builtin_offsetof() expression's constness to evaluation time, too. Furthermore, carry an array index expression's constness flags through the implicit cast to size_t type. Signed-off-by: Nicolai Stange --- evaluate.c | 13 ++++++++----- expression.c | 3 --- validation/constexpr-offsetof.c | 21 +++++++++++++++++++++ 3 files changed, 29 insertions(+), 8 deletions(-) create mode 100644 validation/constexpr-offsetof.c diff --git a/evaluate.c b/evaluate.c index e3b08e4..d32f5a4 100644 --- a/evaluate.c +++ b/evaluate.c @@ -3001,7 +3001,6 @@ static struct symbol *evaluate_offsetof(struct expression *expr) } ctype = field; expr->type = EXPR_VALUE; - expr->flags = EXPR_FLAG_NONE; expr_set_flag(&expr->flags, EXPR_FLAG_INT_CONST_EXPR); expr->value = offset; expr->taint = 0; @@ -3020,7 +3019,6 @@ static struct symbol *evaluate_offsetof(struct expression *expr) ctype = ctype->ctype.base_type; if (!expr->index) { expr->type = EXPR_VALUE; - expr->flags = EXPR_FLAG_NONE; expr_set_flag(&expr->flags, EXPR_FLAG_INT_CONST_EXPR); expr->value = 0; expr->taint = 0; @@ -3028,13 +3026,18 @@ static struct symbol *evaluate_offsetof(struct expression *expr) } else { struct expression *idx = expr->index, *m; struct symbol *i_type = evaluate_expression(idx); + unsigned old_idx_flags; int i_class = classify_type(i_type, &i_type); + if (!is_int(i_class)) { expression_error(expr, "non-integer index"); return NULL; } unrestrict(idx, i_class, &i_type); + old_idx_flags = idx->flags; idx = cast_to(idx, size_t_ctype); + idx->flags |= old_idx_flags; + expr_flags_decay_consts(&idx->flags); m = alloc_const_expression(expr->pos, bits_to_bytes(ctype->bit_size)); m->ctype = size_t_ctype; @@ -3045,19 +3048,19 @@ static struct symbol *evaluate_offsetof(struct expression *expr) expr->op = '*'; expr->ctype = size_t_ctype; expr->flags = m->flags & idx->flags; + expr_flags_decay_consts(&expr->flags); } } if (e) { struct expression *copy = __alloc_expression(0); - unsigned char flags_mask = EXPR_FLAG_NONE; *copy = *expr; if (e->type == EXPR_OFFSETOF) e->in = ctype; if (!evaluate_expression(e)) return NULL; expr->type = EXPR_BINOP; - expr_set_flag(&flags_mask, EXPR_FLAG_INT_CONST_EXPR); - expr->flags = e->flags & copy->flags & flags_mask; + expr->flags = e->flags & copy->flags; + expr_flags_decay_consts(&expr->flags); expr->op = '+'; expr->ctype = size_t_ctype; expr->left = copy; diff --git a/expression.c b/expression.c index b82a036..4ecc865 100644 --- a/expression.c +++ b/expression.c @@ -199,7 +199,6 @@ static struct token *builtin_offsetof_expr(struct token *token, return expect(token, ')', "at end of __builtin_offset"); case SPECIAL_DEREFERENCE: e = alloc_expression(token->pos, EXPR_OFFSETOF); - expr_set_flag(&e->flags, EXPR_FLAG_INT_CONST_EXPR); e->op = '['; *p = e; p = &e->down; @@ -207,7 +206,6 @@ static struct token *builtin_offsetof_expr(struct token *token, case '.': token = token->next; e = alloc_expression(token->pos, EXPR_OFFSETOF); - expr_set_flag(&e->flags, EXPR_FLAG_INT_CONST_EXPR); e->op = '.'; if (token_type(token) != TOKEN_IDENT) { sparse_error(token->pos, "Expected member name"); @@ -219,7 +217,6 @@ static struct token *builtin_offsetof_expr(struct token *token, case '[': token = token->next; e = alloc_expression(token->pos, EXPR_OFFSETOF); - expr_set_flag(&e->flags, EXPR_FLAG_INT_CONST_EXPR); e->op = '['; token = parse_expression(token, &e->index); token = expect(token, ']', diff --git a/validation/constexpr-offsetof.c b/validation/constexpr-offsetof.c new file mode 100644 index 0000000..d1697b0 --- /dev/null +++ b/validation/constexpr-offsetof.c @@ -0,0 +1,21 @@ +struct A { + int a[1]; + int b; +}; + +extern int c; + +static int o[] = { + [__builtin_offsetof(struct A, b)] = 0, // OK + [__builtin_offsetof(struct A, a[0])] = 0, // OK + [__builtin_offsetof(struct A, a[0*0])] = 0, // OK + [__builtin_offsetof(struct A, a[c])] = 0 // KO +}; + +/* + * check-name: __builtin_offsetof() constness verification. + * + * check-error-start +constexpr-offsetof.c:12:39: error: bad constant expression + * check-error-end + */ -- 2.7.0