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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/111050] [11/12/13/14 Regression] ABI break in _Hash_node_value_base since GCC 11 Date: Tue, 12 Sep 2023 16:07:09 +0000 [thread overview] Message-ID: <bug-111050-4-VKAYsfQcWo@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-111050-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111050 --- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> --- Right. The _M_valptr() function compiles to something like: return (_Value*)((char*)this + offsetof(_Hash_node_value_base, _M_storage); In GCC 10, the offsetof expression was non-zero, specifically it was sizeof(_Hash_node_base). So the _M_valptr() function emitted by GCC 10 expected to access the storage member at a non-zero offset to the 'this' pointer pointing to the _Hash_node_value_base subobject. In GCC 11+ the offsetof expression is zero, so the definition of _M_valptr() emitted by GCC 11 does something different. That's an ABI break. If the linker chooses the GCC 10 definition of the function, but the function gets called with a 'this' pointer from GCC 11 code, it will apply the non-zero offset when it shouldn't (and vice versa).
next prev parent reply other threads:[~2023-09-12 16:07 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-17 14:40 [Bug libstdc++/111050] New: " rs2740 at gmail dot com 2023-08-17 15:03 ` [Bug libstdc++/111050] " redi at gcc dot gnu.org 2023-08-18 6:42 ` rguenth at gcc dot gnu.org 2023-09-01 20:33 ` fdumont at gcc dot gnu.org 2023-09-01 23:17 ` rs2740 at gmail dot com 2023-09-02 7:20 ` fdumont at gcc dot gnu.org 2023-09-06 17:17 ` fdumont at gcc dot gnu.org 2023-09-06 18:15 ` rs2740 at gmail dot com 2023-09-06 18:19 ` rs2740 at gmail dot com 2023-09-08 17:04 ` rs2740 at gmail dot com 2023-09-11 11:52 ` redi at gcc dot gnu.org 2023-09-11 16:59 ` frs.dumont at gmail dot com 2023-09-12 15:54 ` john at drouhard dot dev 2023-09-12 16:07 ` redi at gcc dot gnu.org [this message] 2023-09-28 17:24 ` cvs-commit at gcc dot gnu.org 2023-10-02 20:44 ` cvs-commit at gcc dot gnu.org 2023-10-02 20:47 ` cvs-commit at gcc dot gnu.org 2023-10-02 20:48 ` cvs-commit at gcc dot gnu.org 2023-10-03 9:31 ` redi at gcc dot gnu.org
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