Date: Sat, 25 Apr 2026 14:20:21 +0000 From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 4fc1fdd206c3 - main - Merge commit c1d26c3c2510 from llvm git (by Nikolas Klauser): Message-ID: <69eccda5.3774c.179ff3ae@gitrepo.freebsd.org>
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The branch main has been updated by dim: URL: https://cgit.FreeBSD.org/src/commit/?id=4fc1fdd206c3db60ca521e3966f31044c7711398 commit 4fc1fdd206c3db60ca521e3966f31044c7711398 Author: Dimitry Andric <dim@FreeBSD.org> AuthorDate: 2026-03-12 13:24:01 +0000 Commit: Dimitry Andric <dim@FreeBSD.org> CommitDate: 2026-04-25 14:14:22 +0000 Merge commit c1d26c3c2510 from llvm git (by Nikolas Klauser): [libc++] Fix iostream size ABI break (#185839) In #124103 we changed the size of various iostream objects, which turns out to be ABI breaking when compiling non-PIE code. This ABI break is safe to fix, since for any programs allocating more memory for the iostream objects, the remaining bytes are simply unused now. Fixes #185724 This fixes the ABI break that causes programs that use the standard streams to terminate in various interesting ways, usually by throwing an unexpected std::bad_cast exception. PR: 292067 MFC after: 1 month --- contrib/llvm-project/libcxx/src/iostream.cpp | 93 +++++++++++++++++----------- 1 file changed, 56 insertions(+), 37 deletions(-) diff --git a/contrib/llvm-project/libcxx/src/iostream.cpp b/contrib/llvm-project/libcxx/src/iostream.cpp index 416725235c34..b216c6ad35da 100644 --- a/contrib/llvm-project/libcxx/src/iostream.cpp +++ b/contrib/llvm-project/libcxx/src/iostream.cpp @@ -16,24 +16,40 @@ _LIBCPP_BEGIN_NAMESPACE_STD +// This file implements the various stream objects provided inside <iostream>. We're doing some ODR violations in here, +// so this quite fragile. Specifically, the size of the stream objects (i.e. cout, cin etc.) needs to stay the same. +// For that reason, we have `stream` and `stream_data` separated into two objects. The public `stream` objects only +// contain the actual stream, while the private `stream_data` objects contains the `basic_streambuf` we're using as well +// as the mbstate_t. `stream_data` objects are only accessible within the library, so they aren't ABI sensitive and we +// can change them as we want. + +template <class StreamT> +union stream { + constexpr stream() {} + stream(const stream&) = delete; + stream& operator=(const stream&) = delete; + constexpr ~stream() {} + + StreamT value; +}; + template <class StreamT, class BufferT> union stream_data { constexpr stream_data() {} constexpr ~stream_data() {} struct { - // The stream has to be the first element, since that's referenced by the stream declarations in <iostream> - StreamT stream; BufferT buffer; mbstate_t mb; }; - - void init(FILE* stdstream) { - mb = {}; - std::construct_at(&buffer, stdstream, &mb); - std::construct_at(&stream, &buffer); - } }; +template <class StreamT, class BufferT> +void init_stream(FILE* stdstream, stream<StreamT>& stream, stream_data<StreamT, BufferT>& data) { + data.mb = {}; + std::construct_at(&data.buffer, stdstream, &data.mb); + std::construct_at(&stream.value, &data.buffer); +} + #define CHAR_MANGLING_char "D" #define CHAR_MANGLING_wchar_t "_W" #define CHAR_MANGLING(CharT) CHAR_MANGLING_##CharT @@ -46,25 +62,28 @@ union stream_data { #ifdef _LIBCPP_ABI_MICROSOFT # define STREAM(StreamT, BufferT, CharT, var) \ - STRING_DATA_CONSTINIT stream_data<StreamT<CharT>, BufferT<CharT>> var __asm__( \ + STRING_DATA_CONSTINIT stream_data<StreamT<CharT>, BufferT<CharT>> var##_data; \ + _LIBCPP_EXPORTED_FROM_ABI STRING_DATA_CONSTINIT stream<StreamT<CharT>> var __asm__( \ "?" #var "@" ABI_NAMESPACE_STR "@std@@3V?$" #StreamT \ "@" CHAR_MANGLING(CharT) "U?$char_traits@" CHAR_MANGLING(CharT) "@" ABI_NAMESPACE_STR "@std@@@12@A") #else -# define STREAM(StreamT, BufferT, CharT, var) STRING_DATA_CONSTINIT stream_data<StreamT<CharT>, BufferT<CharT>> var +# define STREAM(StreamT, BufferT, CharT, var) \ + STRING_DATA_CONSTINIT stream_data<StreamT<CharT>, BufferT<CharT>> var##_data; \ + _LIBCPP_EXPORTED_FROM_ABI STRING_DATA_CONSTINIT stream<StreamT<CharT>> var #endif // These definitions and the declarations in <iostream> technically cause ODR violations, since they have different // types (stream_data and {i,o}stream respectively). This means that <iostream> should never be included in this TU. -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_istream, __stdinbuf, char, cin); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, char, cout); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, char, cerr); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, char, clog); +STREAM(basic_istream, __stdinbuf, char, cin); +STREAM(basic_ostream, __stdoutbuf, char, cout); +STREAM(basic_ostream, __stdoutbuf, char, cerr); +STREAM(basic_ostream, __stdoutbuf, char, clog); #if _LIBCPP_HAS_WIDE_CHARACTERS -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_istream, __stdinbuf, wchar_t, wcin); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, wchar_t, wcout); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, wchar_t, wcerr); -_LIBCPP_EXPORTED_FROM_ABI STREAM(basic_ostream, __stdoutbuf, wchar_t, wclog); +STREAM(basic_istream, __stdinbuf, wchar_t, wcin); +STREAM(basic_ostream, __stdoutbuf, wchar_t, wcout); +STREAM(basic_ostream, __stdoutbuf, wchar_t, wcerr); +STREAM(basic_ostream, __stdoutbuf, wchar_t, wclog); #endif // _LIBCPP_HAS_WIDE_CHARACTERS // Pretend we're inside a system header so the compiler doesn't flag the use of the init_priority @@ -98,34 +117,34 @@ public: DoIOSInit::DoIOSInit() { force_locale_initialization(); - cin.init(stdin); - cout.init(stdout); - cerr.init(stderr); - clog.init(stderr); + init_stream(stdin, cin, cin_data); + init_stream(stdout, cout, cout_data); + init_stream(stderr, cerr, cerr_data); + init_stream(stderr, clog, clog_data); - cin.stream.tie(&cout.stream); - std::unitbuf(cerr.stream); - cerr.stream.tie(&cout.stream); + cin.value.tie(&cout.value); + std::unitbuf(cerr.value); + cerr.value.tie(&cout.value); #if _LIBCPP_HAS_WIDE_CHARACTERS - wcin.init(stdin); - wcout.init(stdout); - wcerr.init(stderr); - wclog.init(stderr); - - wcin.stream.tie(&wcout.stream); - std::unitbuf(wcerr.stream); - wcerr.stream.tie(&wcout.stream); + init_stream(stdin, wcin, wcin_data); + init_stream(stdout, wcout, wcout_data); + init_stream(stderr, wcerr, wcerr_data); + init_stream(stderr, wclog, wclog_data); + + wcin.value.tie(&wcout.value); + std::unitbuf(wcerr.value); + wcerr.value.tie(&wcout.value); #endif } DoIOSInit::~DoIOSInit() { - cout.stream.flush(); - clog.stream.flush(); + cout.value.flush(); + clog.value.flush(); #if _LIBCPP_HAS_WIDE_CHARACTERS - wcout.stream.flush(); - wclog.stream.flush(); + wcout.value.flush(); + wclog.value.flush(); #endif }home | help
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