public inbox for libstdc++-cvs@sourceware.org help / color / mirror / Atom feed
From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r14-8792] libstdc++: Replace padding bits with bit-fields in __format::_Spec Date: Sun, 4 Feb 2024 21:47:49 +0000 (GMT) [thread overview] Message-ID: <20240204214749.7A1ED3858CDB@sourceware.org> (raw) https://gcc.gnu.org/g:260a22de4fa3d4ad3bb0d3ef2cd45d7f03eb3160 commit r14-8792-g260a22de4fa3d4ad3bb0d3ef2cd45d7f03eb3160 Author: Jonathan Wakely <jwakely@redhat.com> Date: Thu Feb 1 11:09:29 2024 +0000 libstdc++: Replace padding bits with bit-fields in __format::_Spec This ensures that the unused bits will be zero-initialized reliably, and so can be used later by assigning them values in formatter specializations. For example, formatters for std::chrono will need to use an extra bit for a boolean flag to optimize the conversions between locale encodings and UTF-8. Adding the 16-bit _M_reserved2 bit-field results in an increased size for targets that use 1- or 2-byte alignment for all integral types, e.g. cris-elf or m68k. Placing that member before the _M_width member adjusts the layout for all targets, but keeps all the bit-fields together. We can't make that change once C++20 support is ABI stable and non-experimental, so do it now before GCC 14 is released. The _M_fill data member already change from char to char32_t in r14-6991-g37a4c5c23a270c so _Spec is already incompatible with gcc-13 anyway. libstdc++-v3/ChangeLog: * include/std/format (__format::_Spec::_M_reserved): Define new bit-field members to reserve padding bits for future extensions. Diff: --- libstdc++-v3/include/std/format | 2 ++ 1 file changed, 2 insertions(+) diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format index 0eca8b58bfa8..961441e355b3 100644 --- a/libstdc++-v3/include/std/format +++ b/libstdc++-v3/include/std/format @@ -406,6 +406,8 @@ namespace __format _WidthPrec _M_width_kind : 2; _WidthPrec _M_prec_kind : 2; _Pres_type _M_type : 4; + unsigned _M_reserved : 1; + unsigned _M_reserved2 : 16; unsigned short _M_width; unsigned short _M_prec; char32_t _M_fill = ' ';
reply other threads:[~2024-02-04 21:47 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20240204214749.7A1ED3858CDB@sourceware.org \ --to=redi@gcc.gnu.org \ --cc=gcc-cvs@gcc.gnu.org \ --cc=libstdc++-cvs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).