From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by sourceware.org (Postfix) with ESMTPS id 748A33856DD2 for ; Tue, 2 Aug 2022 07:03:55 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 748A33856DD2 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id C581134773; Tue, 2 Aug 2022 07:03:53 +0000 (UTC) Received: from wotan.suse.de (wotan.suse.de [10.160.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 649852C141; Tue, 2 Aug 2022 07:03:53 +0000 (UTC) Date: Tue, 2 Aug 2022 07:03:53 +0000 (UTC) From: Richard Biener To: Qing Zhao cc: gcc-patches Paul A Clarke via , jakub Jelinek , martin Sebor , kees Cook , "joseph@codesourcery.com" Subject: Re: [GCC13][Patch][V2][1/2]Add a new option -fstrict-flex-array[=n] and attribute strict_flex_array(n) and use it in PR101836 In-Reply-To: <567D133A-E24A-4107-A843-95D2ED07ACF2@oracle.com> Message-ID: References: <567D133A-E24A-4107-A843-95D2ED07ACF2@oracle.com> User-Agent: Alpine 2.22 (LSU 394 2020-01-19) MIME-Version: 1.0 X-Spam-Status: No, score=-10.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_NUMSUBJECT, KAM_SHORT, 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 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 02 Aug 2022 07:04:01 -0000 On Mon, 1 Aug 2022, Qing Zhao wrote: > > > > On Aug 1, 2022, at 3:38 AM, Richard Biener wrote: > > > > On Fri, 29 Jul 2022, Qing Zhao wrote: > > > >> Hi, Richard, > >> > >> Thanks a lot for your comments and suggestions. (And sorry for my late reply). > >> > >>> On Jul 28, 2022, at 3:26 AM, Richard Biener wrote: > >>> > >>> On Tue, 19 Jul 2022, Qing Zhao wrote: > >>> > >>>> From 3854004802b8e2f132ebf218fc35a632f5e80c6a Mon Sep 17 00:00:00 2001 > >>>> From: Qing Zhao > >>>> Date: Mon, 18 Jul 2022 17:04:12 +0000 > >>>> Subject: [PATCH 1/2] Add a new option -fstrict-flex-array[=n] and new > >>>> attribute strict_flex_array > >>>> > >>>> Add the following new option -fstrict-flex-array[=n] and a corresponding > >>>> attribute strict_flex_array to GCC: > >>>> > >>>> '-fstrict-flex-array' > >>>> Treat the trailing array of a structure as a flexible array member > >>>> in a stricter way. The positive form is equivalent to > >>>> '-fstrict-flex-array=3', which is the strictest. A trailing array > >>>> is treated as a flexible array member only when it is declared as a > >>>> flexible array member per C99 standard onwards. The negative form > >>>> is equivalent to '-fstrict-flex-array=0', which is the least > >>>> strict. All trailing arrays of structures are treated as flexible > >>>> array members. > >>>> > >>>> '-fstrict-flex-array=LEVEL' > >>>> Treat the trailing array of a structure as a flexible array member > >>>> in a stricter way. The value of LEVEL controls the level of > >>>> strictness. > >>>> > >>>> The possible values of LEVEL are the same as for the > >>>> 'strict_flex_array' attribute (*note Variable Attributes::). > >>>> > >>>> You can control this behavior for a specific trailing array field > >>>> of a structure by using the variable attribute 'strict_flex_array' > >>>> attribute (*note Variable Attributes::). > >>>> > >>>> 'strict_flex_array (LEVEL)' > >>>> The 'strict_flex_array' attribute should be attached to the > >>>> trailing array field of a structure. It specifies the level of > >>>> strictness of treating the trailing array field of a structure as a > >>>> flexible array member. LEVEL must be an integer betwen 0 to 3. > >>>> > >>>> LEVEL=0 is the least strict level, all trailing arrays of > >>>> structures are treated as flexible array members. LEVEL=3 is the > >>>> strictest level, only when the trailing array is declared as a > >>>> flexible array member per C99 standard onwards ([]), it is treated > >>>> as a flexible array member. > >>>> > >>>> There are two more levels in between 0 and 3, which are provided to > >>>> support older codes that use GCC zero-length array extension ([0]) > >>>> or one-size array as flexible array member ([1]): When LEVEL is 1, > >>>> the trailing array is treated as a flexible array member when it is > >>>> declared as either [], [0], or [1]; When LEVEL is 2, the trailing > >>>> array is treated as a flexible array member when it is declared as > >>>> either [], or [0]. > >>>> > >>>> This attribute can be used with or without '-fstrict-flex-array'. > >>>> When both the attribute and the option present at the same time, > >>>> the level of the strictness for the specific trailing array field > >>>> is determined by the attribute. > >>>> > >>>> gcc/c-family/ChangeLog: > >>>> > >>>> * c-attribs.cc (handle_strict_flex_array_attribute): New function. > >>>> (c_common_attribute_table): New item for strict_flex_array. > >>>> * c.opt (fstrict-flex-array): New option. > >>>> (fstrict-flex-array=): New option. > >>>> > >>>> gcc/c/ChangeLog: > >>>> > >>>> * c-decl.cc (add_flexible_array_elts_to_size): Call new utility > >>>> routine flexible_array_member_p. > >>>> (is_flexible_array_member_p): New function. > >>>> (finish_struct): Set the new DECL_NOT_FLEXARRAY flag. > >>>> > >>>> gcc/ChangeLog: > >>>> > >>>> * doc/extend.texi: Document strict_flex_array attribute. > >>>> * doc/invoke.texi: Document -fstrict-flex-array[=n] option. > >>>> * tree-core.h (struct tree_decl_common): New bit field > >>>> decl_not_flexarray. > >>>> * tree.cc (component_ref_size): Reorg by using new utility functions. > >>>> (flexible_array_member_p): New function. > >>>> (zero_length_array_p): Likewise. > >>>> (one_element_array_p): Likewise. > >>>> (flexible_array_type_p): Likewise. > >>>> * tree.h (DECL_NOT_FLEXARRAY): New flag. > >>>> (zero_length_array_p): New function prototype. > >>>> (one_element_array_p): Likewise. > >>>> (flexible_array_member_p): Likewise. > >>>> > >>>> gcc/testsuite/ChangeLog: > >>>> > >>>> * gcc.dg/strict-flex-array-1.c: New test. > >>>> --- > >>>> gcc/c-family/c-attribs.cc | 47 ++++++++ > >>>> gcc/c-family/c.opt | 7 ++ > >>>> gcc/c/c-decl.cc | 91 +++++++++++++-- > >>>> gcc/doc/extend.texi | 25 ++++ > >>>> gcc/doc/invoke.texi | 27 ++++- > >>>> gcc/testsuite/gcc.dg/strict-flex-array-1.c | 31 +++++ > >>>> gcc/tree-core.h | 5 +- > >>>> gcc/tree.cc | 130 ++++++++++++++------- > >>>> gcc/tree.h | 16 ++- > >>>> 9 files changed, 322 insertions(+), 57 deletions(-) > >>>> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-1.c > >>>> > >>>> diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc > >>>> index c8d96723f4c..10d16532f0d 100644 > >>>> --- a/gcc/c-family/c-attribs.cc > >>>> +++ b/gcc/c-family/c-attribs.cc > >>>> @@ -101,6 +101,8 @@ static tree handle_special_var_sec_attribute (tree *, tree, tree, int, bool *); > >>>> static tree handle_aligned_attribute (tree *, tree, tree, int, bool *); > >>>> static tree handle_warn_if_not_aligned_attribute (tree *, tree, tree, > >>>> int, bool *); > >>>> +static tree handle_strict_flex_array_attribute (tree *, tree, tree, > >>>> + int, bool *); > >>>> static tree handle_weak_attribute (tree *, tree, tree, int, bool *) ; > >>>> static tree handle_noplt_attribute (tree *, tree, tree, int, bool *) ; > >>>> static tree handle_alias_ifunc_attribute (bool, tree *, tree, tree, bool *); > >>>> @@ -367,6 +369,8 @@ const struct attribute_spec c_common_attribute_table[] = > >>>> attr_aligned_exclusions }, > >>>> { "warn_if_not_aligned", 0, 1, false, false, false, false, > >>>> handle_warn_if_not_aligned_attribute, NULL }, > >>>> + { "strict_flex_array", 1, 1, false, false, false, false, > >>>> + handle_strict_flex_array_attribute, NULL }, > >>>> { "weak", 0, 0, true, false, false, false, > >>>> handle_weak_attribute, NULL }, > >>>> { "noplt", 0, 0, true, false, false, false, > >>>> @@ -2498,6 +2502,49 @@ handle_warn_if_not_aligned_attribute (tree *node, tree name, > >>>> no_add_attrs, true); > >>>> } > >>>> > >>>> +/* Handle a "strict_flex_array" attribute; arguments as in > >>>> + struct attribute_spec.handler. */ > >>>> + > >>>> +static tree > >>>> +handle_strict_flex_array_attribute (tree *node, tree name, > >>>> + tree args, int ARG_UNUSED (flags), > >>>> + bool *no_add_attrs) > >>>> +{ > >>>> + tree decl = *node; > >>>> + tree argval = TREE_VALUE (args); > >>>> + > >>>> + /* This attribute only applies to field decls of a structure. */ > >>>> + if (TREE_CODE (decl) != FIELD_DECL) > >>>> + { > >>>> + error_at (DECL_SOURCE_LOCATION (decl), > >>>> + "%qE attribute may not be specified for %q+D", name, decl); > >>>> + *no_add_attrs = true; > >>>> + } > >>>> + /* This attribute only applies to field with array type. */ > >>>> + else if (TREE_CODE (TREE_TYPE (decl)) != ARRAY_TYPE) > >>>> + { > >>>> + error_at (DECL_SOURCE_LOCATION (decl), > >>>> + "%qE attribute may not be specified for a non array field", > >>>> + name); > >>>> + *no_add_attrs = true; > >>>> + } > >>>> + else if (TREE_CODE (argval) != INTEGER_CST) > >>>> + { > >>>> + error_at (DECL_SOURCE_LOCATION (decl), > >>>> + "%qE attribute argument not an integer", name); > >>>> + *no_add_attrs = true; > >>>> + } > >>>> + else if (!tree_fits_uhwi_p (argval) || tree_to_uhwi (argval) > 3) > >>>> + { > >>>> + error_at (DECL_SOURCE_LOCATION (decl), > >>>> + "%qE attribute argument %qE is not an integer constant" > >>>> + " between 0 and 3", name, argval); > >>>> + *no_add_attrs = true; > >>>> + } > >>>> + > >>>> + return NULL_TREE; > >>>> +} > >>>> + > >>>> /* Handle a "weak" attribute; arguments as in > >>>> struct attribute_spec.handler. */ > >>>> > >>>> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt > >>>> index 44e1a60ce24..864cd8df1d3 100644 > >>>> --- a/gcc/c-family/c.opt > >>>> +++ b/gcc/c-family/c.opt > >>>> @@ -2060,6 +2060,13 @@ fsized-deallocation > >>>> C++ ObjC++ Var(flag_sized_deallocation) Init(-1) > >>>> Enable C++14 sized deallocation support. > >>>> > >>>> +fstrict-flex-array > >>>> +C C++ Common Alias(fstrict-flex-array=,3,0) > >>>> + > >>>> +fstrict-flex-array= > >>>> +C C++ Common Joined RejectNegative UInteger Var(flag_strict_flex_array) Init(0) IntegerRange(0,3) > >>>> +-fstrict-flex-array= Treat the trailing array of a structure as a flexible array in a stricter way. The default is treating all trailing arrays of structures as flexible arrays. > >>>> + > >>>> fsquangle > >>>> C++ ObjC++ WarnRemoved > >>>> > >>>> diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc > >>>> index ae8990c138f..14defae9584 100644 > >>>> --- a/gcc/c/c-decl.cc > >>>> +++ b/gcc/c/c-decl.cc > >>>> @@ -5013,10 +5013,7 @@ add_flexible_array_elts_to_size (tree decl, tree init) > >>>> > >>>> elt = CONSTRUCTOR_ELTS (init)->last ().value; > >>>> type = TREE_TYPE (elt); > >>>> - if (TREE_CODE (type) == ARRAY_TYPE > >>>> - && TYPE_SIZE (type) == NULL_TREE > >>>> - && TYPE_DOMAIN (type) != NULL_TREE > >>>> - && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE) > >>>> + if (flexible_array_member_p (type)) > >>>> { > >>>> complete_array_type (&type, elt, false); > >>>> DECL_SIZE (decl) > >>>> @@ -8720,6 +8717,80 @@ finish_incomplete_vars (tree incomplete_vars, bool toplevel) > >>>> } > >>>> } > >>>> > >>>> +/* Determine whether the FIELD_DECL X is a flexible array member according to > >>>> + the following info: > >>>> + A. whether the FIELD_DECL X is the last field of the DECL_CONTEXT; > >>>> + B. whether the FIELD_DECL is an array that is declared as "[]", "[0]", > >>>> + or "[1]"; > >>>> + C. flag_strict_flex_array; > >>>> + D. the attribute strict_flex_array that is attached to the field > >>>> + if presenting. > >>>> + Return TRUE when it's a flexible array member, FALSE otherwise. */ > >>>> + > >>>> +static bool > >>>> +is_flexible_array_member_p (bool is_last_field, > >>>> + tree x) > >>>> +{ > >>>> + /* if not the last field, return false. */ > >>>> + if (!is_last_field) > >>>> + return false; > >>>> + > >>>> + /* if not an array field, return false. */ > >>>> + if (TREE_CODE (TREE_TYPE (x)) != ARRAY_TYPE) > >>>> + return false; > >>>> + > >>>> + bool is_zero_length_array = zero_length_array_p (TREE_TYPE (x)); > >>>> + bool is_one_element_array = one_element_array_p (TREE_TYPE (x)); > >>>> + bool is_flexible_array = flexible_array_member_p (TREE_TYPE (x)); > >>>> + > >>>> + unsigned int strict_flex_array_level = flag_strict_flex_array; > >>>> + > >>>> + tree attr_strict_flex_array = lookup_attribute ("strict_flex_array", > >>>> + DECL_ATTRIBUTES (x)); > >>>> + /* if there is a strict_flex_array attribute attached to the field, > >>>> + override the flag_strict_flex_array. */ > >>>> + if (attr_strict_flex_array) > >>>> + { > >>>> + /* get the value of the level first from the attribute. */ > >>>> + unsigned HOST_WIDE_INT attr_strict_flex_array_level = 0; > >>>> + gcc_assert (TREE_VALUE (attr_strict_flex_array) != NULL_TREE); > >>>> + attr_strict_flex_array = TREE_VALUE (attr_strict_flex_array); > >>>> + gcc_assert (TREE_VALUE (attr_strict_flex_array) != NULL_TREE); > >>>> + attr_strict_flex_array = TREE_VALUE (attr_strict_flex_array); > >>>> + gcc_assert (tree_fits_uhwi_p (attr_strict_flex_array)); > >>>> + attr_strict_flex_array_level = tree_to_uhwi (attr_strict_flex_array); > >>>> + > >>>> + /* the attribute has higher priority than flag_struct_flex_array. */ > >>>> + strict_flex_array_level = attr_strict_flex_array_level; > >>>> + } > >>>> + > >>>> + switch (strict_flex_array_level) > >>>> + { > >>>> + case 0: > >>>> + /* default, all trailing arrays are flexiable array members. */ > >>>> + return true; > >>>> + case 1: > >>>> + /* Level 1: all "[1]", "[0]", and "[]" are flexiable array members. */ > >>>> + if (is_one_element_array) > >>>> + return true; > >>>> + /* FALLTHROUGH. */ > >>>> + case 2: > >>>> + /* Level 2: all "[0]", and "[]" are flexiable array members. */ > >>>> + if (is_zero_length_array) > >>>> + return true; > >>>> + /* FALLTHROUGH. */ > >>>> + case 3: > >>>> + /* Level 3: Only "[]" are flexible array members. */ > >>>> + if (is_flexible_array) > >>>> + return true; > >>>> + break; > >>>> + default: > >>>> + gcc_unreachable (); > >>>> + } > >>>> + return false; > >>>> +} > >>>> + > >>>> + > >>>> /* Fill in the fields of a RECORD_TYPE or UNION_TYPE node, T. > >>>> LOC is the location of the RECORD_TYPE or UNION_TYPE's definition. > >>>> FIELDLIST is a chain of FIELD_DECL nodes for the fields. > >>>> @@ -8781,6 +8852,8 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, > >>>> bool saw_named_field = false; > >>>> for (x = fieldlist; x; x = DECL_CHAIN (x)) > >>>> { > >>>> + bool is_last_field = (DECL_CHAIN (x) == NULL_TREE); > >>>> + > >>>> if (TREE_TYPE (x) == error_mark_node) > >>>> continue; > >>>> > >>>> @@ -8819,10 +8892,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, > >>>> DECL_PACKED (x) = 1; > >>>> > >>>> /* Detect flexible array member in an invalid context. */ > >>>> - if (TREE_CODE (TREE_TYPE (x)) == ARRAY_TYPE > >>>> - && TYPE_SIZE (TREE_TYPE (x)) == NULL_TREE > >>>> - && TYPE_DOMAIN (TREE_TYPE (x)) != NULL_TREE > >>>> - && TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (x))) == NULL_TREE) > >>>> + if (flexible_array_member_p (TREE_TYPE (x))) > >>>> { > >>>> if (TREE_CODE (t) == UNION_TYPE) > >>>> { > >>>> @@ -8830,7 +8900,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, > >>>> "flexible array member in union"); > >>>> TREE_TYPE (x) = error_mark_node; > >>>> } > >>>> - else if (DECL_CHAIN (x) != NULL_TREE) > >>>> + else if (!is_last_field) > >>>> { > >>>> error_at (DECL_SOURCE_LOCATION (x), > >>>> "flexible array member not at end of struct"); > >>>> @@ -8850,6 +8920,9 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes, > >>>> pedwarn (DECL_SOURCE_LOCATION (x), OPT_Wpedantic, > >>>> "invalid use of structure with flexible array member"); > >>>> > >>>> + /* Set DECL_NOT_FLEXARRAY flag for FIELD_DECL x. */ > >>>> + DECL_NOT_FLEXARRAY (x) = !is_flexible_array_member_p (is_last_field, x); > >>>> + > >>>> if (DECL_NAME (x) > >>>> || RECORD_OR_UNION_TYPE_P (TREE_TYPE (x))) > >>>> saw_named_field = true; > >>>> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi > >>>> index dfbe33ac652..7451410a011 100644 > >>>> --- a/gcc/doc/extend.texi > >>>> +++ b/gcc/doc/extend.texi > >>>> @@ -7436,6 +7436,31 @@ This warning can be disabled by @option{-Wno-if-not-aligned}. > >>>> The @code{warn_if_not_aligned} attribute can also be used for types > >>>> (@pxref{Common Type Attributes}.) > >>>> > >>>> +@cindex @code{strict_flex_array} variable attribute > >>>> +@item strict_flex_array (@var{level}) > >>>> +The @code{strict_flex_array} attribute should be attached to the trailing > >>>> +array field of a structure. It specifies the level of strictness of > >>>> +treating the trailing array field of a structure as a flexible array > >>>> +member. @var{level} must be an integer betwen 0 to 3. > >>>> + > >>>> +@var{level}=0 is the least strict level, all trailing arrays of structures > >>>> +are treated as flexible array members. @var{level}=3 is the strictest level, > >>>> +only when the trailing array is declared as a flexible array member per C99 > >>>> +standard onwards ([]), it is treated as a flexible array member. > >>> > >>> How is level 3 (thus -fstrict-flex-array) interpreted when you specify > >>> -std=c89? How for -std=gnu89? > >> > >> 1. what’s the major difference between -std=c89 and -std=gnu89 on flexible array? (Checked online, cannot find a concrete answer on this). > >> ** my understanding is: -std=c89 will not support any flexible array (neither [], [0], [1]), but -std=gnu89 will support [0] and [1], but not []. > >> Is this correct? > > > > Yes. > > > >> If my answer to the first question is correct, then: > >> > >> 2. When -fstrict-flex-array=n and -std=c89 present at the same time, which one has the higher priority? > >> ** I think that -std=c89 should be honored over -fstrict-flex-array, therefore we should disable -fstrict-flex-array=n when n > 0 and issue warnings to the user. > >> > >> > >> 3. how about -fstrict-flex-array=n and -std=gnu89 present at the same time? > >> ** When -std=gnu89 present, [] is not supported. So, we need to issue an warning to disable -fstrict-flex-array=3; but level 1 and level 2 is Okay. > >> > >> We also need to document the above. > >> > >> Let me know if you have any more comment and suggestions here. > > > > In my opinion -fstrict-flex-array only makes sense with C99 and above. > > The extra sub-levels allowing [0] or [1] are of questionable benefit. > The multiple-levels control for -fstrict-flex-arrays was an agreement on the discussion of PR101836: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 > > Please see comment#17 till #25 for the details. > > A summary of the discussion is: (Please comment on the following paragraph if you see any issue with it) > > ===== > Flexible Array Member (FAM) is a feature introduced in the C99 standard of the C language in May 2000. It's used as the last element of a structure which is really a header for a variable-length object. > This feature was officially standardized in C99. However, compilers (GCC, Micorsoft compiler, etc.) supported this feature well before C99, with the following variants: > A. trailing zero-length array of a structure was treated as FAM. > Before C99, a valid GCC extension, zero-length array was used to support flexible array member. See more details at: https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html. > B. trailing one-element array of a structure was treated as FAM. > In the absence of the zero-length array extension, in ISO C90, one-element arrays at the end of structures were used to represent FAMs as a convertion. > C. any trailing array of a structure was treated as FAM. > Even earlier time, in the absence of both zero-length array GCC extension and one-element array convention, all trailing arrays of structures could be used as a FAM. > As a result, older codes (before C99) might include any of the above variants (A, B, and C) to represent FAMs. > Another complication is C++, standard C++ doesn't allow either C99 flexible array members or zero-length array. A C++ programmer has to use the GCC zero-length array extension or one-element array convention for the purpose of FAM. > ===== > > As mentioned by Jakub in comment #25: > > "differentiating between only allowing [] as flex, or [] and [0], > or [], [0] and [1], or any trailing array is useful." OK. > > > > I think that with -fstrict-flex-array we're missing a -Wstrict-flex-array > > that would diagnose accesses that are no longer treated as flex array > > access but would be without -fstrict-flex-array? The goal of > > -fstrict-flex-array + -Wstrict-flex-array is to make code standard > > conformant, no? Not to enable extra optimization for [1] arrays when > > we know [0] is used as flexarray? > > Yes, I agree, and this will make the feature more complete and more > useful to help users to get rid of the non-standard-comforming styles. > > Please see comments #23, #35 > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836#c23 > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836#c35 > > A summary is: > > ==== > I think that -Wstrict-flex-arrays will need to be cooperated with -fstrict-flex-arrays=N, i.e, only when -fstrict-flex-arrays=N is presenting, -Wstrict-flex-arrays will be valid and report the warnings when see a [0], or [1], or any trailing array based on N: > > when -fstrict-flex-arrays > =0, -Wstrict-flex-arrays will NOT issue any warnings; > =1, -Wstrict-flex-arrays will issue warnings when an array ref's index is larger than the upper bounds of a trailing array that is a regular trailing array; > =2, -Wstrict-flex-arrays will issue warnings when an array ref's index is larger than the upper bounds of a trailing array that is a regular trailing array or [1]; > =3, -Wstrict-flex-arrays will issue warnings when an array ref's index is larger than the upper bounds of a trailing array that is a regular trailing array or [1], or [0]. > > let me know if you have any comment and suggestion on this. > > ==== Ah, I see - good that this has been discussed. -Wstrict-flex-array shouldn't be a requirement for -fstrict-flex-array to go in, but it would be nice to followup with an implementation for the above (it might be tricky to find a good place for it, but eventually it sounds like -Warray-bounds diagnosing places could eventually be adjusted) > > > > >>> > >>>> + > >>>> +There are two more levels in between 0 and 3, which are provided to support > >>>> +older codes that use GCC zero-length array extension ([0]) or one-size array > >>>> +as flexible array member ([1]): > >>>> +When @var{level} is 1, the trailing array is treated as a flexible array member > >>>> +when it is declared as either "[]", "[0]", or "[1]"; > >>>> +When @var{level} is 2, the trailing array is treated as a flexible array member > >>>> +when it is declared as either "[]", or "[0]". > >>> > >>> Given the above does adding level 2 make sense given that [0] is a GNU > >>> extension? > >> I think Kees already answered this question. > >>> > >>>> +This attribute can be used with or without @option{-fstrict-flex-array}. When > >>>> +both the attribute and the option present at the same time, the level of the > >>>> +strictness for the specific trailing array field is determined by the attribute. > >>>> + > >>>> + > >>>> @item alloc_size (@var{position}) > >>>> @itemx alloc_size (@var{position-1}, @var{position-2}) > >>>> @cindex @code{alloc_size} variable attribute > >>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > >>>> index 94fe57aa4e2..9befe601817 100644 > >>>> --- a/gcc/doc/invoke.texi > >>>> +++ b/gcc/doc/invoke.texi > >>>> @@ -207,7 +207,8 @@ in the following sections. > >>>> -fopenmp -fopenmp-simd @gol > >>>> -fpermitted-flt-eval-methods=@var{standard} @gol > >>>> -fplan9-extensions -fsigned-bitfields -funsigned-bitfields @gol > >>>> --fsigned-char -funsigned-char -fsso-struct=@var{endianness}} > >>>> +-fsigned-char -funsigned-char -fstrict-flex-array[=@var{n}] @gol > >>>> +-fsso-struct=@var{endianness}} > >>>> > >>>> @item C++ Language Options > >>>> @xref{C++ Dialect Options,,Options Controlling C++ Dialect}. > >>>> @@ -2825,6 +2826,30 @@ The type @code{char} is always a distinct type from each of > >>>> @code{signed char} or @code{unsigned char}, even though its behavior > >>>> is always just like one of those two. > >>>> > >>>> +@item -fstrict-flex-array > >>>> +@opindex fstrict-flex-array > >>>> +@opindex fno-strict-flex-array > >>>> +Treat the trailing array of a structure as a flexible array member in a > >>>> +stricter way. > >>>> +The positive form is equivalent to @option{-fstrict-flex-array=3}, which is the > >>>> +strictest. A trailing array is treated as a flexible array member only when it > >>>> +is declared as a flexible array member per C99 standard onwards. > >>>> +The negative form is equivalent to @option{-fstrict-flex-array=0}, which is the > >>>> +least strict. All trailing arrays of structures are treated as flexible array > >>>> +members. > >>>> + > >>>> +@item -fstrict-flex-array=@var{level} > >>>> +@opindex fstrict-flex-array=@var{level} > >>>> +Treat the trailing array of a structure as a flexible array member in a > >>>> +stricter way. The value of @var{level} controls the level of strictness. > >>>> + > >>>> +The possible values of @var{level} are the same as for the > >>>> +@code{strict_flex_array} attribute (@pxref{Variable Attributes}). > >>>> + > >>>> +You can control this behavior for a specific trailing array field of a > >>>> +structure by using the variable attribute @code{strict_flex_array} attribute > >>>> +(@pxref{Variable Attributes}). > >>>> + > >>>> @item -fsso-struct=@var{endianness} > >>>> @opindex fsso-struct > >>>> Set the default scalar storage order of structures and unions to the > >>>> diff --git a/gcc/testsuite/gcc.dg/strict-flex-array-1.c b/gcc/testsuite/gcc.dg/strict-flex-array-1.c > >>>> new file mode 100644 > >>>> index 00000000000..ec886c99b25 > >>>> --- /dev/null > >>>> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-1.c > >>>> @@ -0,0 +1,31 @@ > >>>> +/* testing the correct usage of attribute strict_flex_array. */ > >>>> +/* { dg-do compile } */ > >>>> +/* { dg-options "-O2" } */ > >>>> + > >>>> + > >>>> +int x __attribute__ ((strict_flex_array (1))); /* { dg-error "'strict_flex_array' attribute may not be specified for 'x'" } */ > >>>> + > >>>> +struct trailing { > >>>> + int a; > >>>> + int c __attribute ((strict_flex_array)); /* { dg-error "wrong number of arguments specified for 'strict_flex_array' attribute" } */ > >>>> +}; > >>>> + > >>>> +struct trailing_1 { > >>>> + int a; > >>>> + int b; > >>>> + int c __attribute ((strict_flex_array (2))); /* { dg-error "'strict_flex_array' attribute may not be specified for a non array field" } */ > >>>> +}; > >>>> + > >>>> +extern int d; > >>>> + > >>>> +struct trailing_array_2 { > >>>> + int a; > >>>> + int b; > >>>> + int c[1] __attribute ((strict_flex_array (d))); /* { dg-error "'strict_flex_array' attribute argument not an integer" } */ > >>>> +}; > >>>> + > >>>> +struct trailing_array_3 { > >>>> + int a; > >>>> + int b; > >>>> + int c[0] __attribute ((strict_flex_array (5))); /* { dg-error "'strict_flex_array' attribute argument '5' is not an integer constant between 0 and 3" } */ > >>>> +}; > >>>> diff --git a/gcc/tree-core.h b/gcc/tree-core.h > >>>> index ea9f281f1cc..458c6e6ceea 100644 > >>>> --- a/gcc/tree-core.h > >>>> +++ b/gcc/tree-core.h > >>>> @@ -1813,7 +1813,10 @@ struct GTY(()) tree_decl_common { > >>>> TYPE_WARN_IF_NOT_ALIGN. */ > >>>> unsigned int warn_if_not_align : 6; > >>>> > >>>> - /* 14 bits unused. */ > >>>> + /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY. */ > >>>> + unsigned int decl_not_flexarray : 1; > >>>> + > >>>> + /* 13 bits unused. */ > >>> > >>> I've not seen it so you are probably missing it - the bit has to be > >>> streamed in tree-streamer-{in,out}.cc to be usable from LTO. > >> > >> You mean add it to the routine “unpack_ts_decl_common_value_fields” of tree-streamer-in.cc > >> And “pack_ts_decl_common_value_fields” of tree-streamer-out.cc? > > > > Yes. > > > >> > >>> C++ module streaming also needs to handle it. > >> > >> Which file is for this C++ module streaming? > > > > Not sure, maybe cp/module.cc > > Just checked this file, looks like it’s “Experimental”: > /* C++ modules. Experimental! > > Is it used right now? To whom I can consult with to get more detail on C++? There's testsuite in g++.dg/modules/, Nathan Sidwell should know since he implemented it. > > > >>> > >>>> > >>>> /* UID for points-to sets, stable over copying from inlining. */ > >>>> unsigned int pt_uid; > >>>> diff --git a/gcc/tree.cc b/gcc/tree.cc > >>>> index 84000dd8b69..02e274699fb 100644 > >>>> --- a/gcc/tree.cc > >>>> +++ b/gcc/tree.cc > >>>> @@ -12862,7 +12862,7 @@ get_initializer_for (tree init, tree decl) > >>>> /* Determines the size of the member referenced by the COMPONENT_REF > >>>> REF, using its initializer expression if necessary in order to > >>>> determine the size of an initialized flexible array member. > >>>> - If non-null, set *ARK when REF refers to an interior zero-length > >>>> + If non-null, set *SAM when REF refers to an interior zero-length > >>>> array or a trailing one-element array. > >>>> Returns the size as sizetype (which might be zero for an object > >>>> with an uninitialized flexible array member) or null if the size > >>>> @@ -12878,16 +12878,32 @@ component_ref_size (tree ref, special_array_member *sam /* = NULL */) > >>>> sam = &sambuf; > >>>> *sam = special_array_member::none; > >>>> > >>>> + /* Whether this ref is an array at the end of a structure. */ > >>>> + bool trailing = array_at_struct_end_p (ref); > >>>> + > >>> > >>> actually array_at_struct_end_p returns whether ref possibly refers to > >>> a trailing array. In particular it may return false for arrays at > >>> struct end with a known length as in a.b[i] for the reference to global > >>> 'a': > >>> > >>> struct { int b[1]; } a; > >> > >> Yes, I noticed this behavior during my recent debugging of this routine. I thought it’s a bug and planned to file another bug against it. > >> Looks like that this is an expected behavior. > >> > >> Then I really feel the name and the comments of the routine is very confusing… > >> Shall we change the name of this routine to a more descriptive one? For example, “flexible_array_member_p”? > > > > Note the routine is about classifying a concrete reference, so a better > > name could be flex_array_ref_p (). The name change should be done > > separately (if at all). > > Okay. > > > > >>> > >>> so in the end it should be array_at_struct_end_p also honoring > >>> DECL_NOT_FLEXARRAY. > >> > >> Then it’s make more sense to check DECL_NOT_FLEXARRAY inside this utility routine? > > > > Yes. > > > >>> > >>>> /* The object/argument referenced by the COMPONENT_REF and its type. */ > >>>> tree arg = TREE_OPERAND (ref, 0); > >>>> tree argtype = TREE_TYPE (arg); > >>>> - /* The referenced member. */ > >>>> - tree member = TREE_OPERAND (ref, 1); > >>>> > >>>> + /* The referenced field member. */ > >>>> + tree member = TREE_OPERAND (ref, 1); > >>>> + tree memtype = TREE_TYPE (member); > >>>> tree memsize = DECL_SIZE_UNIT (member); > >>>> + > >>>> + bool is_zero_length_array_ref = zero_length_array_p (memtype); > >>>> + bool is_constant_length_array_ref = false; > >>>> + bool is_one_element_array_ref > >>>> + = one_element_array_p (memtype, &is_constant_length_array_ref); > >>>> + > >>>> + /* Determine the type of the special array member. */ > >>>> + if (is_zero_length_array_ref) > >>>> + *sam = trailing ? special_array_member::trail_0 > >>>> + : special_array_member::int_0; > >>>> + else if (is_one_element_array_ref && trailing) > >>>> + *sam = special_array_member::trail_1; > >>>> + > >>>> if (memsize) > >>>> { > >>>> - tree memtype = TREE_TYPE (member); > >>>> if (TREE_CODE (memtype) != ARRAY_TYPE) > >>>> /* DECL_SIZE may be less than TYPE_SIZE in C++ when referring > >>>> to the type of a class with a virtual base which doesn't > >>>> @@ -12897,50 +12913,30 @@ component_ref_size (tree ref, special_array_member *sam /* = NULL */) > >>>> return (tree_int_cst_equal (memsize, TYPE_SIZE_UNIT (memtype)) > >>>> ? memsize : NULL_TREE); > >>>> > >>>> - bool trailing = array_at_struct_end_p (ref); > >>>> - bool zero_length = integer_zerop (memsize); > >>>> - if (!trailing && !zero_length) > >>>> + if (!trailing && !is_zero_length_array_ref) > >>>> /* MEMBER is either an interior array or is an array with > >>>> more than one element. */ > >>>> return memsize; > >>>> > >>>> - if (zero_length) > >>>> - { > >>>> - if (trailing) > >>>> - *sam = special_array_member::trail_0; > >>>> - else > >>>> - { > >>>> - *sam = special_array_member::int_0; > >>>> - memsize = NULL_TREE; > >>>> - } > >>>> - } > >>>> + if (*sam != special_array_member::trail_1 > >>>> + && is_constant_length_array_ref) > >>>> + /* MEMBER is a constant length array which is not a one-element > >>>> + trailing array. */ > >>>> + return memsize; > >>>> > >>>> - if (!zero_length) > >>>> - if (tree dom = TYPE_DOMAIN (memtype)) > >>>> - if (tree min = TYPE_MIN_VALUE (dom)) > >>>> - if (tree max = TYPE_MAX_VALUE (dom)) > >>>> - if (TREE_CODE (min) == INTEGER_CST > >>>> - && TREE_CODE (max) == INTEGER_CST) > >>>> - { > >>>> - offset_int minidx = wi::to_offset (min); > >>>> - offset_int maxidx = wi::to_offset (max); > >>>> - offset_int neltsm1 = maxidx - minidx; > >>>> - if (neltsm1 > 0) > >>>> - /* MEMBER is an array with more than one element. */ > >>>> - return memsize; > >>>> - > >>>> - if (neltsm1 == 0) > >>>> - *sam = special_array_member::trail_1; > >>>> - } > >>>> + if (*sam == special_array_member::int_0) > >>>> + memsize = NULL_TREE; > >>>> > >>>> - /* For a reference to a zero- or one-element array member of a union > >>>> - use the size of the union instead of the size of the member. */ > >>>> + /* For a reference to a flexible array member, an interior zero length > >>>> + array, or an array with variable length of a union, use the size of > >>>> + the union instead of the size of the member. */ > >>>> if (TREE_CODE (argtype) == UNION_TYPE) > >>>> memsize = TYPE_SIZE_UNIT (argtype); > >>>> } > >>>> > >>>> - /* MEMBER is either a bona fide flexible array member, or a zero-length > >>>> - array member, or an array of length one treated as such. */ > >>>> + /* MEMBER now is a flexible array member, an interior zero length array, or > >>>> + an array with variable length. We need to decide its size from its > >>>> + initializer. */ > >>>> > >>>> /* If the reference is to a declared object and the member a true > >>>> flexible array, try to determine its size from its initializer. */ > >>>> @@ -14351,6 +14347,59 @@ default_is_empty_record (const_tree type) > >>>> return is_empty_type (TYPE_MAIN_VARIANT (type)); > >>>> } > >>>> > >>>> +/* Determine whether TYPE is a ISO flexible array memeber type "[]". */ > >>> > >>> ISO C99 > >> > >> Okay, will add this. > >>> > >>>> +bool > >>>> +flexible_array_member_p (const_tree type) > >>> > >>> since you pass in a type a better name would be > >>> flexible_array_type_p? > >> Okay, how about “flexible_array_member_type_p”? (Since “flexible array member” is a complete concept). > > > > works for me > > > >>> > >>>> +{ > >>>> + if (TREE_CODE (type) == ARRAY_TYPE > >>>> + && TYPE_SIZE (type) == NULL_TREE > >>>> + && TYPE_DOMAIN (type) != NULL_TREE > >>> > >>> why require a specified TYPE_DOMAIN? > >> > >> There are multiple places in the current GCC used the following sequence: > >> > >> - if (TREE_CODE (type)) == ARRAY_TYPE > >> - && TYPE_SIZE (type) == NULL_TREE > >> - && TYPE_DOMAIN (type) != NULL_TREE > >> - && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE) > >> > >> To check whether the type is a flexible_array_member type. > >> (For example, the routine “add_flexible_array_elts_to_size” in c/c-decl.cc > >> the routine “finish_struct” in c/c-decl.cc > >> the routine “flexible_array_type_p” in tree.cc) > >> > >> That’s the reason I come up with this common routine to replace all these sequences. > >> > >> > >>>> + && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE) > >>> > >>> and why a NULL TYPE_MAX_VALUE? Isn't an unknown TYPE_SIZE enough? > >> > >> Does the current FE generate such IR for a []? An array type, without TYPE_SIZE, with a TYPE_DOMAIN, but the MAX_VALUE of the TYPE_DOMAIN is NULL? > >> > >>> > >>> That said, I'm not sure providing this abstraction is a good idea > >>> given the use I see is in frontend code. > >> > >> This one is also used in middle-end, for example “flexible_array_type_p” in tree.cc. > > > > That was originally in c-decl.c, seems some target wanted to use it. The > > issue with this is that it tests the C frontend way of declaring a flex > > array (and it is used by the frontend), but there are many other possible > > representations the middle-end should classify as flex array. > > > > The Objective C frontend also has a function named this way and it seems > > to be a 1:1 copy :/ > > > > The nios2 use of the function doesn't make much sense to me - externals > > should not end up in _any_ section!? > > What’s you mean by “nios2” ? Not quite understand this sentence. -:) could you explain a little bit? nios2 is one of GCCs target architectures, it was a use in the nios2 backend this function was moved to generic code for but the actual use doesn't really make sense to me ... (it's not your fault of course) > > > > So I'd rather move this function back to where it came from, ideally > > to c-family/, removing the copy in objective C ... > > Okay, I will try this in the next version. > > > >>> > >>>> + return true; > >>>> + > >>>> + return false; > >>>> +} > >>>> + > >>>> +/* Determine whether TYPE is a zero-length array type "[0]". */ > >>>> +bool > >>>> +zero_length_array_p (const_tree type) > >>>> +{ > >>>> + if (TREE_CODE (type) == ARRAY_TYPE) > >>>> + if (tree type_size = TYPE_SIZE_UNIT (type)) > >>>> + if ((integer_zerop (type_size)) > >>>> + && TYPE_DOMAIN (type) != NULL_TREE > >>>> + && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) == NULL_TREE) > >>> > >>> that again seems very C(?) frontend specific, please drop it. > >> Currently, the middle-end utility routine “component_ref_size” need to check zero_length_array, one_element_array, etc, > >> So, this is not only a FE specific routine. > > > > Sigh, it's nother strange function that was introduced just for > > diagnostics (so it's not "correct"), it shouldn't have ended up in > > tree.cc IMHO. > > The codes in GCC to handle flexible array are really messy, I hope that we can make it clean and consistent through this work. > Of course gradually… As said, it's unfortunate to have many APIs doing similar things and I'd rather avoid introducing new APIs (with to me, questionable implementation or general usefulness) when possible. > > > >> And I think that for making the -fstrict-flex-array work clear, we might want to emphasize and distinguish the concepts of > >> > >> [] flexible_array_member_type_p > >> [0] zero_length_array_type_p > >> [1] one_element_array_type_p > >> > >> Across GCC. > > > > Why? > > Because the whole confusion of flexible array handlings in our compiler started from the confusion of these concepts. > During my study of this whole problem, I found that these concepts were really confusion, and after I was finally clear on > These concepts, I started to know how to resolve the whole issue. > > In our GCC doc, https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > > We already have such concepts, but not very clear. > I think making these concepts clear is very important to resolve such messy situation in GCC. > > > The only important thing to the middle-end is whether the > > size of the array is known (aka array_at_struct_end_p). This > > routine classifies it with > > But whether the size of the array is known depends on whether the array is a > > [0], > [1], > [] > > + -fstrict-flex-arrays=n But only array_at_struct_end_p should care and for it we will have DECL_NOT_FLEXARRAY. And frontends may have different ideas how they represent [0], [1] or [] (and in fact they do). The rest of the middle-end really should _not_ care. > > > > > /* The array now is at struct end. Treat flexible arrays as > > always subject to extend, even into just padding constrained by > > an underlying decl. */ > > if (! TYPE_SIZE (atype) > > || ! TYPE_DOMAIN (atype) > > || ! TYPE_MAX_VALUE (TYPE_DOMAIN (atype))) > > return true; > > This sequence is only for identifying []. Right? > > The [0] and [1] is not handled by the above. Yes. But also int a[1:] would be identified this way, other frontends like Ada or Fortran have means to more elaborately specify array dimensions. > > > > any flexible_array_member_type_p that covers a different subset of > > flex-array types would be hugely confusing. > > Don’t quite understand this sentence... I mean if array_at_struct_end_p decides sth is a flex array reference but flexible_array_member_type_p on the type decides it is not, that would be confusing. Thus if adding such new API then it should be possible to use it from array_at_struct_end_p, removing then some of the redundant checks there. > > > >> > >>> > >>>> + return true; > >>>> + return false; > >>>> +} > >>>> + > >>>> +/* Determine whether TYPE is a one-element array type "[1]". > >>>> + Set IS_CONSTANT_LENGTH to true if the length is constant, > >>>> + otherwise, IS_CONSTANT_LENGTH is set to false. */ > >>>> +bool > >>>> +one_element_array_p (const_tree type, bool *is_constant_length /* = NULL */) > >>>> +{ > >>>> + if (is_constant_length) > >>>> + *is_constant_length = false; > >>>> + > >>>> + if (TREE_CODE (type) == ARRAY_TYPE) > >>>> + if (tree dom = TYPE_DOMAIN (type)) > >>>> + if (tree min = TYPE_MIN_VALUE (dom)) > >>>> + if (tree max = TYPE_MAX_VALUE (dom)) > >>>> + if (TREE_CODE (min) == INTEGER_CST > >>>> + && TREE_CODE (max) == INTEGER_CST) > >>>> + { > >>>> + offset_int minidx = wi::to_offset (min); > >>>> + offset_int maxidx = wi::to_offset (max); > >>>> + offset_int neltsm1 = maxidx - minidx; > >>>> + if (is_constant_length) > >>>> + *is_constant_length = true; > >>>> + if (neltsm1 == 0) > >>>> + return true; > >>>> + } > >>> > >>> I'd say likewise. Maybe move them to c-family/c-common.{cc,h} instead > >>> in a more specialized way for the single use you have? > >> > >> It’s not single use, it’s also used in “component_ref_size” routine. > > > > Don't copy from a routine that's not designed to be "correct”. > > Okay…. > > > > In > > fact the middle-end already has array_type_nelts, so one_element_array_p > > can be written as integer_zerop (array_type_nelts (type)). It also > > has the comment > > > > /* TYPE_MAX_VALUE may not be set if the array has unknown length. */ > > if (!max) > > { > > /* zero sized arrays are represented from C FE as complete types > > with > > NULL TYPE_MAX_VALUE and zero TYPE_SIZE, while C++ FE represents > > them as min 0, max -1. */ > > if (COMPLETE_TYPE_P (type) > > && integer_zerop (TYPE_SIZE (type)) > > && integer_zerop (min)) > > return build_int_cst (TREE_TYPE (min), -1); > > Thanks for the info, I will check on the above, and rewrite “one_element_array_p” with “array_type_nelts”. > > Qing > > > > Richard. > > > >> Thanks a lot for your comments. > >> > >> Qing > >>> > >>>> + return false; > >>>> +} > >>>> + > >>>> /* Determine whether TYPE is a structure with a flexible array member, > >>>> or a union containing such a structure (possibly recursively). */ > >>>> > >>>> @@ -14367,10 +14416,7 @@ flexible_array_type_p (const_tree type) > >>>> last = x; > >>>> if (last == NULL_TREE) > >>>> return false; > >>>> - if (TREE_CODE (TREE_TYPE (last)) == ARRAY_TYPE > >>>> - && TYPE_SIZE (TREE_TYPE (last)) == NULL_TREE > >>>> - && TYPE_DOMAIN (TREE_TYPE (last)) != NULL_TREE > >>>> - && TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (last))) == NULL_TREE) > >>>> + if (flexible_array_member_p (TREE_TYPE (last))) > >>>> return true; > >>>> return false; > >>>> case UNION_TYPE: > >>>> diff --git a/gcc/tree.h b/gcc/tree.h > >>>> index e6564aaccb7..3107de5b499 100644 > >>>> --- a/gcc/tree.h > >>>> +++ b/gcc/tree.h > >>>> @@ -2993,6 +2993,11 @@ extern void decl_value_expr_insert (tree, tree); > >>>> #define DECL_PADDING_P(NODE) \ > >>>> (FIELD_DECL_CHECK (NODE)->decl_common.decl_flag_3) > >>>> > >>>> +/* Used in a FIELD_DECL to indicate whether this field is not a flexible > >>>> + array member. */ > >>>> +#define DECL_NOT_FLEXARRAY(NODE) \ > >>>> + (FIELD_DECL_CHECK (NODE)->decl_common.decl_not_flexarray) > >>>> + > >>>> /* A numeric unique identifier for a LABEL_DECL. The UID allocation is > >>>> dense, unique within any one function, and may be used to index arrays. > >>>> If the value is -1, then no UID has been assigned. */ > >>>> @@ -5531,10 +5536,10 @@ extern tree component_ref_field_offset (tree); > >>>> returns null. */ > >>>> enum struct special_array_member > >>>> { > >>>> - none, /* Not a special array member. */ > >>>> - int_0, /* Interior array member with size zero. */ > >>>> - trail_0, /* Trailing array member with size zero. */ > >>>> - trail_1 /* Trailing array member with one element. */ > >>>> + none, /* Not a special array member. */ > >>>> + int_0, /* Interior array member with size zero. */ > >>>> + trail_0, /* Trailing array member with size zero. */ > >>>> + trail_1 /* Trailing array member with one element. */ > >>>> }; > >>>> > >>>> /* Return the size of the member referenced by the COMPONENT_REF, using > >>>> @@ -6489,6 +6494,9 @@ extern void gt_pch_nx (tree &, gt_pointer_operator, void *); > >>>> extern bool nonnull_arg_p (const_tree); > >>>> extern bool is_empty_type (const_tree); > >>>> extern bool default_is_empty_record (const_tree); > >>>> +extern bool zero_length_array_p (const_tree); > >>>> +extern bool one_element_array_p (const_tree, bool * = NULL); > >>>> +extern bool flexible_array_member_p (const_tree); > >>>> extern bool flexible_array_type_p (const_tree); > >>>> extern HOST_WIDE_INT arg_int_size_in_bytes (const_tree); > >>>> extern tree arg_size_in_bytes (const_tree); > >>>> > >>> > >>> -- > >>> Richard Biener > >>> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, > >>> Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; > >>> HRB 36809 (AG Nuernberg) > >> > >> > > > > -- > > Richard Biener > > SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, > > Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; > > HRB 36809 (AG Nuernberg) > > -- Richard Biener SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)