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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/102024] [12 Regression] zero width bitfields and ABIs Date: Thu, 31 Mar 2022 12:50:22 +0000 [thread overview] Message-ID: <bug-102024-4-PUDIQlyj6d@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-102024-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102024 --- Comment #32 from Jakub Jelinek <jakub at gcc dot gnu.org> --- One of the reasons we changed the ABI on various arches one way or another is that we had this ABI incompatibility between C and C++, that just can't be right. At that time we can and should decide if we go for compatibility with C or C++. The MIPS n64 wording I could find: "Regardless of the struct field structure, it is treated as a sequence of 64-bit chunks. If a chunk consists solely of a double float field (but not a double, which is part of a union), it is passed in a floating point register. Any other chunk is passed in an integer register." is unclear for both the zero width bitfields and empty structure/union C members, members that have zero size and are on the 64-bit chunk boundaries can belong to either previous or next chunk or can be ignored altogether. I think best would be to ignore them altogether, especially if other compilers do that too. Also consider: struct T {}; struct S { struct T t; double a; struct T u; double b; }; struct U { int a[0]; double b; int c[0]; double d; }; argument passing in C (etc.) - in C++ struct T will have size 1 and therefore will be passed differently between C (which pedantically disallows empty structures or zero length arrays) and C++.
next prev parent reply other threads:[~2022-03-31 12:50 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-23 14:36 [Bug target/102024] New: " jakub at gcc dot gnu.org 2021-08-23 14:38 ` [Bug target/102024] [12 Regression] " jakub at gcc dot gnu.org 2021-08-23 14:40 ` jakub at gcc dot gnu.org 2021-08-23 15:20 ` jakub at gcc dot gnu.org 2021-08-23 15:37 ` jakub at gcc dot gnu.org 2021-08-23 16:17 ` rsandifo at gcc dot gnu.org 2021-08-23 20:42 ` segher at gcc dot gnu.org 2021-08-23 20:49 ` segher at gcc dot gnu.org 2021-08-24 7:06 ` rguenth at gcc dot gnu.org 2021-08-24 14:13 ` matz at gcc dot gnu.org 2021-08-24 21:36 ` segher at gcc dot gnu.org 2021-08-25 19:23 ` wschmidt at gcc dot gnu.org 2021-08-25 19:33 ` wschmidt at gcc dot gnu.org 2021-08-25 20:08 ` wschmidt at gcc dot gnu.org 2021-09-03 7:53 ` cvs-commit at gcc dot gnu.org 2021-09-03 8:12 ` jakub at gcc dot gnu.org 2021-09-21 16:16 ` wschmidt at gcc dot gnu.org 2021-09-23 12:40 ` cvs-commit at gcc dot gnu.org 2022-01-10 16:47 ` cvs-commit at gcc dot gnu.org 2022-03-24 9:39 ` ebotcazou at gcc dot gnu.org 2022-03-24 11:25 ` cvs-commit at gcc dot gnu.org 2022-03-29 16:44 ` cvs-commit at gcc dot gnu.org 2022-03-29 16:45 ` cvs-commit at gcc dot gnu.org 2022-03-30 10:27 ` jakub at gcc dot gnu.org 2022-03-30 10:39 ` jakub at gcc dot gnu.org 2022-03-30 12:40 ` hp at gcc dot gnu.org 2022-03-30 12:43 ` jakub at gcc dot gnu.org 2022-03-30 13:05 ` jakub at gcc dot gnu.org 2022-03-30 13:42 ` xry111 at mengyan1223 dot wang 2022-03-30 13:53 ` jakub at gcc dot gnu.org 2022-03-30 14:34 ` xry111 at mengyan1223 dot wang 2022-03-30 19:02 ` xry111 at mengyan1223 dot wang 2022-03-31 12:36 ` segher at gcc dot gnu.org 2022-03-31 12:50 ` jakub at gcc dot gnu.org [this message] 2022-03-31 15:08 ` xry111 at mengyan1223 dot wang 2022-03-31 15:14 ` xry111 at mengyan1223 dot wang 2022-04-01 9:50 ` cvs-commit at gcc dot gnu.org 2022-04-01 14:39 ` cvs-commit at gcc dot gnu.org 2022-04-01 14:39 ` cvs-commit at gcc dot gnu.org 2022-04-02 0:47 ` segher at gcc dot gnu.org 2022-04-27 7:23 ` cvs-commit at gcc dot gnu.org
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