From patchwork Tue Aug 6 12:22:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alejandro Colomar X-Patchwork-Id: 1969461 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=TtXIPNyN; dkim-atps=neutral Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=server2.sourceware.org; envelope-from=gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org; receiver=patchwork.ozlabs.org) Received: from server2.sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4WdXYQ4y6wz1ydt for ; Tue, 6 Aug 2024 22:24:26 +1000 (AEST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 8652E3858414 for ; Tue, 6 Aug 2024 12:24:24 +0000 (GMT) X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by sourceware.org (Postfix) with ESMTPS id AE12B385840F for ; Tue, 6 Aug 2024 12:22:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org AE12B385840F Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=kernel.org ARC-Filter: OpenARC Filter v1.0.0 sourceware.org AE12B385840F Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=145.40.73.55 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1722946981; cv=none; b=oF8a2e9sbplnBjoZ2mFPYIB+ShAfbp36pDJFYM/Pk0A6RzqkrYHO//j0Ww/YSEAk5aFlAeGIlImR6ZG2Mg1q10Jn14ILDxE8xZVaBsSecaKXnj7AE6udnFlE4oSF0W4MsrqC8Xb6y3Bnzy4Bb1IcUV1S58w9udb+vEAwiWTJBVM= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1722946981; c=relaxed/simple; bh=+9eb4I62KYGhyc/Kv2xmP0/ygrnLfnOdqjfBZlSThPs=; h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version; b=r1hrVm92o8FZaLrdQx0NbnJL3BW0me+3CGo948/4jpdzPF7esMKcQNjE0vyLdHsAhFrSSnw5UDuP2PVis0VsQOup09qdKfo30kN9tHbrMkFbQyZOOWVSpYOXQ+MprtJK3Y1yrgsD9WkHH50/6653VCDbKCnGZcDqm74L02jUiD8= ARC-Authentication-Results: i=1; server2.sourceware.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id DE31ECE0E64; Tue, 6 Aug 2024 12:22:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34446C32786; Tue, 6 Aug 2024 12:22:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722946973; bh=+9eb4I62KYGhyc/Kv2xmP0/ygrnLfnOdqjfBZlSThPs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TtXIPNyNKfFUsf0h+A06vcT1LJ8gRGL7dL6H4vg2pv2OMQEyPOIJSlkPmcHoI/qHD NUOJtv0NVB2Q9biZG7Sk/fnDNCxf2lwpip3Q8vkYA2G9n9Ix2Oa3Hsdy7aNX9I1sSj hjCWLoGYc8+HWNlqdrZuRaN+hRmOe6d9s3dqDa57O22LW10lCoykuigfDfEjwXX2Fd hTaRhTpaet1Nq/gSkJc1kV3wnx11Ca+u/X4E4sN7Dc0nstURgpFPZqYJBLCVXateKk 8hD4nlEOKu4ARI5gp8kdsJBIqNIIRHRysU8ty8daC4sZcmcXIZ0/K4Q9BFzdIhn8cA yj62xf434tGAQ== Date: Tue, 6 Aug 2024 14:22:49 +0200 From: Alejandro Colomar To: gcc-patches@gcc.gnu.org Cc: Alejandro Colomar , Xavier Del Campo Romero , Martin Uecker , Gabriel Ravier , Joseph Myers , Jakub Jelinek , Kees Cook , Qing Zhao , Jens Gustedt Subject: [RFC v4 3/4] c: Add __lengthof__() operator (n2529) Message-ID: <20240806122218.3827577-4-alx@kernel.org> X-Mailer: git-send-email 2.45.2 References: <20240728141547.302478-1-alx@kernel.org> <20240806122218.3827577-1-alx@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240806122218.3827577-1-alx@kernel.org> X-Spam-Status: No, score=-9.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org This operator is similar to sizeof() but can only be applied to an array, and returns its length (number of elements). FUTURE DIRECTIONS: We could make it work with array parameters to functions, and somehow magically return the length designator of the array, regardless of it being really a pointer. Link: Link: Suggested-by: Xavier Del Campo Romero Co-developed-by: Martin Uecker Cc: Gabriel Ravier Cc: Joseph Myers Cc: Jakub Jelinek Cc: Kees Cook Cc: Qing Zhao Cc: Jens Gustedt Signed-off-by: Alejandro Colomar --- gcc/c-family/c-common.cc | 26 +++++++++ gcc/c-family/c-common.def | 3 + gcc/c-family/c-common.h | 2 + gcc/c/c-decl.cc | 20 +++++-- gcc/c/c-parser.cc | 61 +++++++++++++++----- gcc/c/c-tree.h | 4 ++ gcc/c/c-typeck.cc | 114 ++++++++++++++++++++++++++++++++++++-- gcc/cp/operators.def | 1 + gcc/doc/extend.texi | 27 +++++++++ gcc/target.h | 3 + 10 files changed, 237 insertions(+), 24 deletions(-) diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc index e7e371fd26f..9f5feb83345 100644 --- a/gcc/c-family/c-common.cc +++ b/gcc/c-family/c-common.cc @@ -465,6 +465,7 @@ const struct c_common_resword c_common_reswords[] = { "__inline", RID_INLINE, 0 }, { "__inline__", RID_INLINE, 0 }, { "__label__", RID_LABEL, 0 }, + { "__lengthof__", RID_LENGTHOF, 0 }, { "__null", RID_NULL, 0 }, { "__real", RID_REALPART, 0 }, { "__real__", RID_REALPART, 0 }, @@ -4070,6 +4071,31 @@ c_alignof_expr (location_t loc, tree expr) return fold_convert_loc (loc, size_type_node, t); } + +/* Implement the lengthof keyword: Return the length of an array, + that is, the number of elements in the array. */ + +tree +c_lengthof_type (location_t loc, tree type) +{ + enum tree_code type_code; + + type_code = TREE_CODE (type); + if (type_code != ARRAY_TYPE) + { + error_at (loc, "invalid application of % to type %qT", type); + return error_mark_node; + } + if (!COMPLETE_TYPE_P (type)) + { + error_at (loc, + "invalid application of % to incomplete type %qT", + type); + return error_mark_node; + } + + return array_type_nelts_top (type); +} /* Handle C and C++ default attributes. */ diff --git a/gcc/c-family/c-common.def b/gcc/c-family/c-common.def index 5de96e5d4a8..6d162f67104 100644 --- a/gcc/c-family/c-common.def +++ b/gcc/c-family/c-common.def @@ -50,6 +50,9 @@ DEFTREECODE (EXCESS_PRECISION_EXPR, "excess_precision_expr", tcc_expression, 1) number. */ DEFTREECODE (USERDEF_LITERAL, "userdef_literal", tcc_exceptional, 3) +/* Represents a 'lengthof' expression. */ +DEFTREECODE (LENGTHOF_EXPR, "lengthof_expr", tcc_expression, 1) + /* Represents a 'sizeof' expression during C++ template expansion, or for the purpose of -Wsizeof-pointer-memaccess warning. */ DEFTREECODE (SIZEOF_EXPR, "sizeof_expr", tcc_expression, 1) diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h index ccaea27c2b9..f815a4cf3bc 100644 --- a/gcc/c-family/c-common.h +++ b/gcc/c-family/c-common.h @@ -105,6 +105,7 @@ enum rid /* C extensions */ RID_ASM, RID_TYPEOF, RID_TYPEOF_UNQUAL, RID_ALIGNOF, RID_ATTRIBUTE, + RID_LENGTHOF, RID_VA_ARG, RID_EXTENSION, RID_IMAGPART, RID_REALPART, RID_LABEL, RID_CHOOSE_EXPR, RID_TYPES_COMPATIBLE_P, RID_BUILTIN_COMPLEX, RID_BUILTIN_SHUFFLE, @@ -885,6 +886,7 @@ extern tree c_common_truthvalue_conversion (location_t, tree); extern void c_apply_type_quals_to_decl (int, tree); extern tree c_sizeof_or_alignof_type (location_t, tree, bool, bool, int); extern tree c_alignof_expr (location_t, tree); +extern tree c_lengthof_type (location_t, tree); /* Print an error message for invalid operands to arith operation CODE. NOP_EXPR is used as a special case (see truthvalue_conversion). */ extern void binary_op_error (rich_location *, enum tree_code, tree, tree); diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc index 4dced430d1f..790c58b2558 100644 --- a/gcc/c/c-decl.cc +++ b/gcc/c/c-decl.cc @@ -8937,12 +8937,16 @@ start_struct (location_t loc, enum tree_code code, tree name, within a statement expr used within sizeof, et. al. This is not terribly serious as C++ doesn't permit statement exprs within sizeof anyhow. */ - if (warn_cxx_compat && (in_sizeof || in_typeof || in_alignof)) + if (warn_cxx_compat && (in_sizeof || in_typeof || in_alignof || in_lengthof)) warning_at (loc, OPT_Wc___compat, "defining type in %qs expression is invalid in C++", (in_sizeof ? "sizeof" - : (in_typeof ? "typeof" : "alignof"))); + : (in_typeof + ? "typeof" + : (in_alignof + ? "alignof" + : "lengthof")))); if (in_underspecified_init) error_at (loc, "%qT defined in underspecified object initializer", ref); @@ -9897,7 +9901,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, struct_types. */ if (warn_cxx_compat && struct_parse_info != NULL - && !in_sizeof && !in_typeof && !in_alignof) + && !in_sizeof && !in_typeof && !in_alignof && !in_lengthof) struct_parse_info->struct_types.safe_push (t); } @@ -10071,12 +10075,16 @@ start_enum (location_t loc, struct c_enum_contents *the_enum, tree name, /* FIXME: This will issue a warning for a use of a type defined within sizeof in a statement expr. This is not terribly serious as C++ doesn't permit statement exprs within sizeof anyhow. */ - if (warn_cxx_compat && (in_sizeof || in_typeof || in_alignof)) + if (warn_cxx_compat && (in_sizeof || in_typeof || in_alignof || in_lengthof)) warning_at (loc, OPT_Wc___compat, "defining type in %qs expression is invalid in C++", (in_sizeof ? "sizeof" - : (in_typeof ? "typeof" : "alignof"))); + : (in_typeof + ? "typeof" + : (in_alignof + ? "alignof" + : "lengthof")))); if (in_underspecified_init) error_at (loc, "%qT defined in underspecified object initializer", @@ -10270,7 +10278,7 @@ finish_enum (tree enumtype, tree values, tree attributes) struct_types. */ if (warn_cxx_compat && struct_parse_info != NULL - && !in_sizeof && !in_typeof && !in_alignof) + && !in_sizeof && !in_typeof && !in_alignof && !in_lengthof) struct_parse_info->struct_types.safe_push (enumtype); /* Check for consistency with previous definition */ diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc index 12c5ed5d92c..09bb19f9299 100644 --- a/gcc/c/c-parser.cc +++ b/gcc/c/c-parser.cc @@ -74,7 +74,17 @@ along with GCC; see the file COPYING3. If not see #include "bitmap.h" #include "analyzer/analyzer-language.h" #include "toplev.h" + +#define c_parser_sizeof_expression(parser) \ +( \ + c_parser_sizeof_or_lengthof_expression (parser, RID_SIZEOF) \ +) +#define c_parser_lengthof_expression(parser) \ +( \ + c_parser_sizeof_or_lengthof_expression (parser, RID_LENGTHOF) \ +) + /* We need to walk over decls with incomplete struct/union/enum types after parsing the whole translation unit. In finish_decl(), if the decl is static, has incomplete @@ -1687,7 +1697,7 @@ static struct c_expr c_parser_binary_expression (c_parser *, struct c_expr *, tree); static struct c_expr c_parser_cast_expression (c_parser *, struct c_expr *); static struct c_expr c_parser_unary_expression (c_parser *); -static struct c_expr c_parser_sizeof_expression (c_parser *); +static struct c_expr c_parser_sizeof_or_lengthof_expression (c_parser *, enum rid); static struct c_expr c_parser_alignof_expression (c_parser *); static struct c_expr c_parser_postfix_expression (c_parser *); static struct c_expr c_parser_postfix_expression_after_paren_type (c_parser *, @@ -9864,6 +9874,8 @@ c_parser_unary_expression (c_parser *parser) case CPP_KEYWORD: switch (c_parser_peek_token (parser)->keyword) { + case RID_LENGTHOF: + return c_parser_lengthof_expression (parser); case RID_SIZEOF: return c_parser_sizeof_expression (parser); case RID_ALIGNOF: @@ -9903,12 +9915,13 @@ c_parser_unary_expression (c_parser *parser) /* Parse a sizeof expression. */ static struct c_expr -c_parser_sizeof_expression (c_parser *parser) +c_parser_sizeof_or_lengthof_expression (c_parser *parser, enum rid rid) { + const char *op_name = (rid == RID_LENGTHOF) ? "lengthof" : "sizeof"; struct c_expr expr; struct c_expr result; location_t expr_loc; - gcc_assert (c_parser_next_token_is_keyword (parser, RID_SIZEOF)); + gcc_assert (c_parser_next_token_is_keyword (parser, rid)); location_t start; location_t finish = UNKNOWN_LOCATION; @@ -9917,7 +9930,10 @@ c_parser_sizeof_expression (c_parser *parser) c_parser_consume_token (parser); c_inhibit_evaluation_warnings++; - in_sizeof++; + if (rid == RID_LENGTHOF) + in_lengthof++; + else + in_sizeof++; if (c_parser_next_token_is (parser, CPP_OPEN_PAREN) && c_token_starts_compound_literal (c_parser_peek_2nd_token (parser))) { @@ -9936,7 +9952,10 @@ c_parser_sizeof_expression (c_parser *parser) { struct c_expr ret; c_inhibit_evaluation_warnings--; - in_sizeof--; + if (rid == RID_LENGTHOF) + in_lengthof--; + else + in_sizeof--; ret.set_error (); ret.original_code = ERROR_MARK; ret.original_type = NULL; @@ -9948,31 +9967,45 @@ c_parser_sizeof_expression (c_parser *parser) type_name, expr_loc); finish = expr.get_finish (); - goto sizeof_expr; + goto Xof_expr; } /* sizeof ( type-name ). */ if (scspecs) - error_at (expr_loc, "storage class specifier in %"); + error_at (expr_loc, "storage class specifier in %qs", op_name); if (type_name->specs->alignas_p) error_at (type_name->specs->locations[cdw_alignas], - "alignment specified for type name in %"); + "alignment specified for type name in %qs", op_name); c_inhibit_evaluation_warnings--; - in_sizeof--; - result = c_expr_sizeof_type (expr_loc, type_name); + if (rid == RID_LENGTHOF) + { + in_lengthof--; + result = c_expr_lengthof_type (expr_loc, type_name); + } + else + { + in_sizeof--; + result = c_expr_sizeof_type (expr_loc, type_name); + } } else { expr_loc = c_parser_peek_token (parser)->location; expr = c_parser_unary_expression (parser); finish = expr.get_finish (); - sizeof_expr: + Xof_expr: c_inhibit_evaluation_warnings--; - in_sizeof--; + if (rid == RID_LENGTHOF) + in_lengthof--; + else + in_sizeof--; mark_exp_read (expr.value); if (TREE_CODE (expr.value) == COMPONENT_REF && DECL_C_BIT_FIELD (TREE_OPERAND (expr.value, 1))) - error_at (expr_loc, "% applied to a bit-field"); - result = c_expr_sizeof_expr (expr_loc, expr); + error_at (expr_loc, "%qs applied to a bit-field", op_name); + if (rid == RID_LENGTHOF) + result = c_expr_lengthof_expr (expr_loc, expr); + else + result = c_expr_sizeof_expr (expr_loc, expr); } if (finish == UNKNOWN_LOCATION) finish = start; diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h index 15da875a029..102fcfefea6 100644 --- a/gcc/c/c-tree.h +++ b/gcc/c/c-tree.h @@ -736,6 +736,7 @@ extern int c_type_dwarf_attribute (const_tree, int); /* in c-typeck.cc */ extern int in_alignof; extern int in_sizeof; +extern int in_lengthof; extern int in_typeof; extern bool c_in_omp_for; extern bool c_omp_array_section_p; @@ -786,6 +787,9 @@ extern tree build_external_ref (location_t, tree, bool, tree *); extern void pop_maybe_used (bool); extern struct c_expr c_expr_sizeof_expr (location_t, struct c_expr); extern struct c_expr c_expr_sizeof_type (location_t, struct c_type_name *); +extern struct c_expr c_expr_lengthof_expr (location_t, struct c_expr); +extern struct c_expr c_expr_lengthof_type (location_t loc, + struct c_type_name *); extern struct c_expr parser_build_unary_op (location_t, enum tree_code, struct c_expr); extern struct c_expr parser_build_binary_op (location_t, diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc index 7e0f01ed22b..69b9f1171ae 100644 --- a/gcc/c/c-typeck.cc +++ b/gcc/c/c-typeck.cc @@ -71,6 +71,9 @@ int in_alignof; /* The level of nesting inside "sizeof". */ int in_sizeof; +/* The level of nesting inside "sizeof". */ +int in_lengthof; + /* The level of nesting inside "typeof". */ int in_typeof; @@ -3255,7 +3258,7 @@ build_external_ref (location_t loc, tree id, bool fun, tree *type) if (TREE_CODE (ref) == FUNCTION_DECL && !in_alignof) { - if (!in_sizeof && !in_typeof) + if (!in_sizeof && !in_typeof && !in_lengthof) C_DECL_USED (ref) = 1; else if (DECL_INITIAL (ref) == NULL_TREE && DECL_EXTERNAL (ref) @@ -3311,7 +3314,7 @@ struct maybe_used_decl { /* The decl. */ tree decl; - /* The level seen at (in_sizeof + in_typeof). */ + /* The level seen at (in_sizeof + in_typeof + in_lengthof). */ int level; /* The next one at this level or above, or NULL. */ struct maybe_used_decl *next; @@ -3329,7 +3332,7 @@ record_maybe_used_decl (tree decl) { struct maybe_used_decl *t = XOBNEW (&parser_obstack, struct maybe_used_decl); t->decl = decl; - t->level = in_sizeof + in_typeof; + t->level = in_sizeof + in_typeof + in_lengthof; t->next = maybe_used_decls; maybe_used_decls = t; } @@ -3343,7 +3346,7 @@ void pop_maybe_used (bool used) { struct maybe_used_decl *p = maybe_used_decls; - int cur_level = in_sizeof + in_typeof; + int cur_level = in_sizeof + in_typeof + in_lengthof; while (p && p->level > cur_level) { if (used) @@ -3453,6 +3456,109 @@ c_expr_sizeof_type (location_t loc, struct c_type_name *t) return ret; } +static bool +is_top_array_vla (tree type) +{ + bool zero, var; + tree d; + + if (TREE_CODE (type) != ARRAY_TYPE) + return false; + if (!COMPLETE_TYPE_P (type)) + return false; + + d = TYPE_DOMAIN (type); + zero = !TYPE_MAX_VALUE (d); + var = (!zero + && (TREE_CODE (TYPE_MIN_VALUE (d)) != INTEGER_CST + || TREE_CODE (TYPE_MAX_VALUE (d)) != INTEGER_CST)); + var = var || (zero && C_TYPE_VARIABLE_SIZE (type)); + return var; +} + +/* Return the result of lengthof applied to EXPR. */ + +struct c_expr +c_expr_lengthof_expr (location_t loc, struct c_expr expr) +{ + struct c_expr ret; + if (expr.value == error_mark_node) + { + ret.value = error_mark_node; + ret.original_code = ERROR_MARK; + ret.original_type = NULL; + ret.m_decimal = 0; + pop_maybe_used (false); + } + else + { + bool expr_const_operands = true; + + tree folded_expr = c_fully_fold (expr.value, require_constant_value, + &expr_const_operands); + ret.value = c_lengthof_type (loc, TREE_TYPE (folded_expr)); + c_last_sizeof_arg = expr.value; + c_last_sizeof_loc = loc; + ret.original_code = LENGTHOF_EXPR; + ret.original_type = NULL; + ret.m_decimal = 0; + if (is_top_array_vla (TREE_TYPE (folded_expr))) + { + /* lengthof is evaluated when given a vla. */ + ret.value = build2 (C_MAYBE_CONST_EXPR, TREE_TYPE (ret.value), + folded_expr, ret.value); + C_MAYBE_CONST_EXPR_NON_CONST (ret.value) = !expr_const_operands; + SET_EXPR_LOCATION (ret.value, loc); + } + pop_maybe_used (is_top_array_vla (TREE_TYPE (folded_expr))); + } + return ret; +} + +/* Return the result of lengthof applied to T, a structure for the type + name passed to _lengthof (rather than the type itself). LOC is the + location of the original expression. */ + +struct c_expr +c_expr_lengthof_type (location_t loc, struct c_type_name *t) +{ + tree type; + struct c_expr ret; + tree type_expr = NULL_TREE; + bool type_expr_const = true; + type = groktypename (t, &type_expr, &type_expr_const); + ret.value = c_lengthof_type (loc, type); + c_last_sizeof_arg = type; + c_last_sizeof_loc = loc; + ret.original_code = LENGTHOF_EXPR; + ret.original_type = NULL; + ret.m_decimal = 0; + if (type == error_mark_node) + { + ret.value = error_mark_node; + ret.original_code = ERROR_MARK; + } + else + if ((type_expr || TREE_CODE (ret.value) == INTEGER_CST) + && is_top_array_vla (type)) + { + /* If the type is a [*] array, it is a VLA but is represented as + having a size of zero. In such a case we must ensure that + the result of lengthof does not get folded to a constant by + c_fully_fold, because if the length is evaluated the result is + not constant and so constraints on zero or negative size + arrays must not be applied when this lengthof call is inside + another array declarator. */ + if (!type_expr) + type_expr = integer_zero_node; + ret.value = build2 (C_MAYBE_CONST_EXPR, TREE_TYPE (ret.value), + type_expr, ret.value); + C_MAYBE_CONST_EXPR_NON_CONST (ret.value) = !type_expr_const; + } + pop_maybe_used (type != error_mark_node ? is_top_array_vla (type) : false); + return ret; +} + /* Build a function call to function FUNCTION with parameters PARAMS. The function call is at LOC. PARAMS is a list--a chain of TREE_LIST nodes--in which the diff --git a/gcc/cp/operators.def b/gcc/cp/operators.def index d8878923602..d640ed8bd91 100644 --- a/gcc/cp/operators.def +++ b/gcc/cp/operators.def @@ -91,6 +91,7 @@ DEF_OPERATOR ("co_await", CO_AWAIT_EXPR, "aw", OVL_OP_FLAG_UNARY) /* These are extensions. */ DEF_OPERATOR ("alignof", ALIGNOF_EXPR, "az", OVL_OP_FLAG_UNARY) +DEF_OPERATOR ("__lengthof__", LENGTHOF_EXPR, "lz", OVL_OP_FLAG_UNARY) DEF_OPERATOR ("__imag__", IMAGPART_EXPR, "v18__imag__", OVL_OP_FLAG_UNARY) DEF_OPERATOR ("__real__", REALPART_EXPR, "v18__real__", OVL_OP_FLAG_UNARY) diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 0b572afca72..6e1d302150d 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -10391,6 +10391,33 @@ If the operand of the @code{__alignof__} expression is a function, the expression evaluates to the alignment of the function which may be specified by attribute @code{aligned} (@pxref{Common Function Attributes}). +@node Length +@section Determining the Length of Arrays +@cindex lengthof +@cindex length +@cindex array length + +The keyword @code{__lengthof__} determines the length of an array operand, +that is, the number of elements in the array. +Its syntax is just like @code{sizeof}. +The operand must be a complete array type. +The operand is not evaluated +if the top-level length designator is an integer constant expression; +and it is evaluated +if the top-level length designator is not an integer constant expression. + +XXX: Do we want to document the following? I think so. +XXX: It would prevent users from relying on __lengthof__ +XXX: for distinguishing arrays from pointers. +XXX: I don't want users to complain in the future +XXX: if this doesn't report errors on function parameters anymore +XXX: and that breaks their assumptions. +In the future, +it might also accept a function parameter with array notation, +an incomplete array whose length is specified by other means, +such as attributes, +or other similar cases. + @node Inline @section An Inline Function is As Fast As a Macro @cindex inline functions diff --git a/gcc/target.h b/gcc/target.h index c1f99b97b86..79890ae9944 100644 --- a/gcc/target.h +++ b/gcc/target.h @@ -245,6 +245,9 @@ enum type_context_kind { /* Directly measuring the alignment of T. */ TCTX_ALIGNOF, + /* Directly measuring the length of array T. */ + TCTX_LENGTHOF, + /* Creating objects of type T with static storage duration. */ TCTX_STATIC_STORAGE,