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From: "siddhesh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/107952] tree-object-size: inconsistent size for flexible arrays nested in structs Date: Wed, 25 Jan 2023 12:44:59 +0000 [thread overview] Message-ID: <bug-107952-4-v0LgEsDyng@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-107952-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107952 --- Comment #12 from Siddhesh Poyarekar <siddhesh at gcc dot gnu.org> --- (In reply to qinzhao from comment #7) > (In reply to Richard Biener from comment #1) > > GCC considered this as a flex-array. > > do you mean for the following example: > > typedef struct { > char pad; > char data[]; > } F2; > > typedef struct { > unsigned pad; > F2 flex; > } S2; > > although C standard disallow the above, GCC extension treats S2.flex.data as > a flex-array? > > How about: > > typedef struct { > char pad; > char data[]; > } F2; > > typedef struct { > F2 flex; > unsigned pad; > } S2; > > do we have any documentation on this Gcc extension? There's an open bug to document these semantics: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77650(In reply to rguenther@suse.de from comment #11) > On Tue, 24 Jan 2023, qing.zhao at oracle dot com wrote: > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107952 > > > > --- Comment #10 from Qing Zhao <qing.zhao at oracle dot com> --- > > > --- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> --- > > > > > > GCC handles for example > > > > > > struct A { char data[1]; }; > > > struct B { int n; struct A a; }; > > > > > > as if the a.data[] array is a flex-array. > > > > Okay. Then the maximum size of __builtin_object_size for it should be -1, > > right? > > I think so. Why? If the a B object is allocated with a visible allocator call, we can return the correct size here too.
next prev parent reply other threads:[~2023-01-25 12:45 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-02 14:04 [Bug tree-optimization/107952] New: " siddhesh at gcc dot gnu.org 2022-12-05 8:05 ` [Bug tree-optimization/107952] " rguenth at gcc dot gnu.org 2022-12-05 12:46 ` siddhesh at gcc dot gnu.org 2022-12-05 13:15 ` jakub at gcc dot gnu.org 2022-12-05 15:11 ` rguenther at suse dot de 2022-12-05 15:28 ` siddhesh at gcc dot gnu.org 2023-01-23 19:39 ` qinzhao at gcc dot gnu.org 2023-01-23 19:44 ` qinzhao at gcc dot gnu.org 2023-01-23 21:30 ` siddhesh at gcc dot gnu.org 2023-01-24 10:04 ` rguenth at gcc dot gnu.org 2023-01-24 15:24 ` qing.zhao at oracle dot com 2023-01-25 7:32 ` rguenther at suse dot de 2023-01-25 12:44 ` siddhesh at gcc dot gnu.org [this message] 2023-01-25 15:14 ` qing.zhao at oracle dot com 2023-01-25 16:12 ` siddhesh at gcc dot gnu.org 2023-01-25 16:40 ` qing.zhao at oracle dot com 2023-01-25 21:16 ` siddhesh at gcc dot gnu.org 2023-01-25 21:43 ` qinzhao at gcc dot gnu.org 2023-01-26 7:20 ` rguenth at gcc dot gnu.org 2023-01-26 22:13 ` qinzhao at gcc dot gnu.org 2023-01-27 7:46 ` rguenther at suse dot de
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