From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 1F5F4385801E; Tue, 12 Mar 2024 14:18:02 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1F5F4385801E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1710253082; bh=cUXFLSr+LT6zzbXGK2XDreJBRm7DbJ44bInKU99C9vE=; h=From:To:Subject:Date:From; b=PQ0iDI1bvPmmyk18eiIEqPfBtXqGtS28yGEAe0VB5rPiEEn0yMiKfbLPeH1Fstxkl FAx/POUgKA94tJB0XZOknNsxBXmIQqZ5cshL+b78hpFOMb2rv7jBzKIlho0Dbe0sXX db/L54DOuCmlQ2BRavmoGX8UvrPIau8cm6r4Y22o= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-8430] libstdc++: Fix std::basic_format_arg::handle for BasicFormatters X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/releases/gcc-13 X-Git-Oldrev: 3c8faeac3d03e032d55fae390618e577c292a83e X-Git-Newrev: 826f7e5ca3bddf3ff82bc52c09e84f5d35b24dbf Message-Id: <20240312141802.1F5F4385801E@sourceware.org> Date: Tue, 12 Mar 2024 14:18:02 +0000 (GMT) List-Id: https://gcc.gnu.org/g:826f7e5ca3bddf3ff82bc52c09e84f5d35b24dbf commit r13-8430-g826f7e5ca3bddf3ff82bc52c09e84f5d35b24dbf Author: Jonathan Wakely Date: Wed Feb 28 15:05:08 2024 +0000 libstdc++: Fix std::basic_format_arg::handle for BasicFormatters std::basic_format_arg::handle is supposed to format its value as const if that is valid, to reduce the number of instantiations of the formatter's format function. I made a silly typo so that it checks formattable_with not formattable_with, which breaks support for BasicFormatters i.e. ones that can only format non-const types. There's a static_assert in the handle constructor which is supposed to improve diagnostics for trying to format a const argument with a formatter that doesn't support it. That condition can't fail, because the std::basic_format_arg constructor is already constrained to check that the argument type is formattable. The static_assert can be removed. libstdc++-v3/ChangeLog: * include/std/format (basic_format_arg::handle::__maybe_const_t): Fix condition to check if const type is formattable. (basic_format_arg::handle::handle(T&)): Remove redundant static_assert. * testsuite/std/format/formatter/basic.cc: New test. (cherry picked from commit 02ca9d3f0c5d2b0255df28f021834dd67ad79bc2) Diff: --- libstdc++-v3/include/std/format | 6 +----- .../testsuite/std/format/formatter/basic.cc | 24 ++++++++++++++++++++++ 2 files changed, 25 insertions(+), 5 deletions(-) diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format index 7bcaddb3715..a938d65a7b9 100644 --- a/libstdc++-v3/include/std/format +++ b/libstdc++-v3/include/std/format @@ -2866,7 +2866,7 @@ namespace __format // Format as const if possible, to reduce instantiations. template using __maybe_const_t - = __conditional_t<__formattable<_Tp>, const _Tp, _Tp>; + = __conditional_t<__formattable, const _Tp, _Tp>; template static void @@ -2884,10 +2884,6 @@ namespace __format explicit handle(_Tp& __val) noexcept { - if constexpr (!__formattable) - static_assert(!is_const_v<_Tp>, "std::format argument must be " - "non-const for this type"); - this->_M_ptr = __builtin_addressof(__val); auto __func = _S_format<__maybe_const_t<_Tp>>; this->_M_func = reinterpret_cast(__func); diff --git a/libstdc++-v3/testsuite/std/format/formatter/basic.cc b/libstdc++-v3/testsuite/std/format/formatter/basic.cc new file mode 100644 index 00000000000..56c18864135 --- /dev/null +++ b/libstdc++-v3/testsuite/std/format/formatter/basic.cc @@ -0,0 +1,24 @@ +// { dg-do compile { target c++20 } } + +// BasicFormatter requirements do not require a const parameter. + +#include + +struct X { }; + +template<> struct std::formatter +{ + constexpr auto parse(format_parse_context& ctx) + { return ctx.begin(); } + + // Takes non-const X& + format_context::iterator format(X&, format_context& ctx) const + { + auto out = ctx.out(); + *out++ = 'x'; + return out; + } +}; + +X x; +auto s = std::format("{}", x);