* Re: [PATCH RFA] libstdc++: add experimental Contracts support
2022-11-18 18:17 ` [PATCH RFA] libstdc++: add experimental Contracts support Jonathan Wakely
@ 2022-11-19 2:40 ` Jason Merrill
2022-11-19 12:50 ` Jonathan Wakely
0 siblings, 1 reply; 3+ messages in thread
From: Jason Merrill @ 2022-11-19 2:40 UTC (permalink / raw)
To: Jonathan Wakely; +Cc: gcc-patches, libstdc++
[-- Attachment #1: Type: text/plain, Size: 13354 bytes --]
On 11/18/22 13:17, Jonathan Wakely wrote:
> On 03/11/22 15:57 -0400, Jason Merrill wrote:
>> Tested x86_64-pc-linux-gnu. OK for trunk?
>>
>> -- >8 --
>>
>> This patch adds the library support for the experimental C++ Contracts
>> implementation. This now consists only of a default definition of the
>> violation handler, which users can override through defining their own
>> version. To avoid ABI stability problems with libstdc++.so this is
>> added to
>> a separate -lstdc++exp static library, which the driver knows to add
>> when it
>> sees -fcontracts.
>>
>> libstdc++-v3/ChangeLog:
>>
>> * acinclude.m4 (glibcxx_SUBDIRS): Add src/experimental.
>> * include/Makefile.am (experimental_headers): Add contract.
>> * include/Makefile.in: Regenerate.
>> * src/Makefile.am (SUBDIRS): Add experimental.
>> * src/Makefile.in: Regenerate.
>> * configure: Regenerate.
>> * src/experimental/contract.cc: New file.
>> * src/experimental/Makefile.am: New file.
>> * src/experimental/Makefile.in: New file.
>> * include/experimental/contract: New file.
>> ---
>> libstdc++-v3/src/experimental/contract.cc | 41 ++
>> libstdc++-v3/acinclude.m4 | 2 +-
>> libstdc++-v3/include/Makefile.am | 1 +
>> libstdc++-v3/include/Makefile.in | 1 +
>> libstdc++-v3/src/Makefile.am | 3 +-
>> libstdc++-v3/src/Makefile.in | 6 +-
>> libstdc++-v3/src/experimental/Makefile.am | 96 +++
>> libstdc++-v3/src/experimental/Makefile.in | 796 +++++++++++++++++++++
>> libstdc++-v3/include/experimental/contract | 84 +++
>> 9 files changed, 1026 insertions(+), 4 deletions(-)
>> create mode 100644 libstdc++-v3/src/experimental/contract.cc
>> create mode 100644 libstdc++-v3/src/experimental/Makefile.am
>> create mode 100644 libstdc++-v3/src/experimental/Makefile.in
>> create mode 100644 libstdc++-v3/include/experimental/contract
>>
>>
>> base-commit: a4cd2389276a30c39034a83d640ce68fa407bac1
>> prerequisite-patch-id: 329bc16a88dc9a3b13cd3fcecb3678826cc592dc
>>
>> diff --git a/libstdc++-v3/src/experimental/contract.cc
>> b/libstdc++-v3/src/experimental/contract.cc
>> new file mode 100644
>> index 00000000000..b9b72cd7df0
>> --- /dev/null
>> +++ b/libstdc++-v3/src/experimental/contract.cc
>> @@ -0,0 +1,41 @@
>> +// -*- C++ -*- std::experimental::contract_violation and friends
>> +// Copyright (C) 1994-2022 Free Software Foundation, Inc.
>
> Copy&paste from an old file? I don't think this uses anything
> existing, should be just 2022.
>
>> +//
>> +// This file is part of GCC.
>> +//
>> +// GCC is free software; you can redistribute it and/or modify
>> +// it under the terms of the GNU General Public License as published by
>> +// the Free Software Foundation; either version 3, or (at your option)
>> +// any later version.
>> +//
>> +// GCC is distributed in the hope that it will be useful,
>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> +// GNU General Public License for more details.
>> +//
>> +// Under Section 7 of GPL version 3, you are granted additional
>> +// permissions described in the GCC Runtime Library Exception, version
>> +// 3.1, as published by the Free Software Foundation.
>> +
>> +// You should have received a copy of the GNU General Public License and
>> +// a copy of the GCC Runtime Library Exception along with this program;
>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
>> +// <http://www.gnu.org/licenses/>.
>> +
>> +#include <experimental/contract>
>> +#include <iostream>
>> +
>> +__attribute__ ((weak)) void
>> +handle_contract_violation (const
>> std::experimental::contract_violation &violation)
>> +{
>> + std::cerr << "default std::handle_contract_violation called: " <<
>> std::endl
>
> No need for flushing with endl here, just \n please.
>
>> + << " " << violation.file_name()
>> + << " " << violation.line_number()
>> + << " " << violation.function_name()
>> + << " " << violation.comment()
>> + << " " << violation.assertion_level()
>> + << " " << violation.assertion_role()
>> + << " " << (int)violation.continuation_mode()
>> + << std::endl;
>
> And this will flush too, which typically isn't needed for stderr
> because it's unbuffered. But somebody could have fiddled with cerr, so
> doing this final flush seems OK.
>
>> +}
>> +
>> diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
>> index 6f672924a73..baf01913a90 100644
>> --- a/libstdc++-v3/acinclude.m4
>> +++ b/libstdc++-v3/acinclude.m4
>> @@ -49,7 +49,7 @@ AC_DEFUN([GLIBCXX_CONFIGURE], [
>> # Keep these sync'd with the list in Makefile.am. The first
>> provides an
>> # expandable list at autoconf time; the second provides an
>> expandable list
>> # (i.e., shell variable) at configure time.
>> - m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98
>> src/c++11 src/c++17 src/c++20 src/filesystem src/libbacktrace doc po
>> testsuite python])
>> + m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98
>> src/c++11 src/c++17 src/c++20 src/filesystem src/libbacktrace
>> src/experimental doc po testsuite python])
>> SUBDIRS='glibcxx_SUBDIRS'
>>
>> # These need to be absolute paths, yet at the same time need to
>> diff --git a/libstdc++-v3/include/Makefile.am
>> b/libstdc++-v3/include/Makefile.am
>> index 96137a6621a..a6f9912cb9b 100644
>> --- a/libstdc++-v3/include/Makefile.am
>> +++ b/libstdc++-v3/include/Makefile.am
>> @@ -769,6 +769,7 @@ experimental_headers = \
>> ${experimental_srcdir}/array \
>> ${experimental_srcdir}/buffer \
>> ${experimental_srcdir}/chrono \
>> + ${experimental_srcdir}/contract \
>> ${experimental_srcdir}/deque \
>> ${experimental_srcdir}/executor \
>> ${experimental_srcdir}/forward_list \
>> diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
>> index b83c222d51d..6f08068326d 100644
>> --- a/libstdc++-v3/src/Makefile.am
>> +++ b/libstdc++-v3/src/Makefile.am
>> @@ -37,7 +37,7 @@ backtrace_supported_h =
>> endif
>>
>> ## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.
>> -SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir) $(backtrace_dir)
>> +SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir) $(backtrace_dir)
>> experimental
>>
>> # Cross compiler support.
>> if VTV_CYGMIN
>> @@ -75,6 +75,7 @@ endif
>> if ENABLE_BACKTRACE
>> vpath % $(top_srcdir)/src/libbacktrace
>> endif
>> +vpath % $(top_srcdir)/src/experimental
>>
>> if GLIBCXX_LDBL_COMPAT
>> ldbl_compat_sources = compatibility-ldbl.cc
>> diff --git a/libstdc++-v3/src/experimental/Makefile.am
>> b/libstdc++-v3/src/experimental/Makefile.am
>> new file mode 100644
>> index 00000000000..a1c2f62a518
>> --- /dev/null
>> +++ b/libstdc++-v3/src/experimental/Makefile.am
>> @@ -0,0 +1,96 @@
>> +## Makefile for experimental additions to the GNU C++ Standard library.
>> +##
>> +## Copyright (C) 2014-2022 Free Software Foundation, Inc.
>> +##
>> +## Process this file with automake to produce Makefile.in.
>> +##
>> +## This file is part of GCC.
>> +##
>> +## GCC is free software; you can redistribute it and/or modify
>> +## it under the terms of the GNU General Public License as published by
>> +## the Free Software Foundation; either version 3, or (at your option)
>> +## any later version.
>> +##
>> +## GCC is distributed in the hope that it will be useful,
>> +## but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> +## GNU General Public License for more details.
>> +##
>> +## You should have received a copy of the GNU General Public License
>> +## along with GCC; see the file COPYING3. If not see
>> +## <http://www.gnu.org/licenses/>.
>> +
>> +include $(top_srcdir)/fragment.am
>> +
>> +toolexeclib_LTLIBRARIES = libstdc++exp.la
>> +
>> +headers =
>> +
>> +sources = \
>> + contract.cc
>> +
>> +# vpath % $(top_srcdir)/src/experimental
>> +
>> +libstdc__exp_la_SOURCES = $(sources)
>> +
>> +# AM_CXXFLAGS needs to be in each subdirectory so that it can be
>> +# modified in a per-library or per-sub-library way. Need to manually
>> +# set this option because CONFIG_CXXFLAGS has to be after
>> +# OPTIMIZE_CXXFLAGS on the compile line so that -O2 can be overridden
>> +# as the occasion calls for it.
>> +AM_CXXFLAGS = \
>> + -std=gnu++17 -nostdinc++ \
>> + $(glibcxx_lt_pic_flag) $(glibcxx_compiler_shared_flag) \
>> + $(XTEMPLATE_FLAGS) $(VTV_CXXFLAGS) \
>> + $(WARN_CXXFLAGS) $(OPTIMIZE_CXXFLAGS) $(CONFIG_CXXFLAGS) \
>> + -fimplicit-templates
>> +
>> +AM_MAKEFLAGS = \
>> + "gxx_include_dir=$(gxx_include_dir)"
>> +
>> +# Libtool notes
>> +
>> +# 1) In general, libtool expects an argument such as `--tag=CXX' when
>> +# using the C++ compiler, because that will enable the settings
>> +# detected when C++ support was being configured. However, when no
>> +# such flag is given in the command line, libtool attempts to figure
>> +# it out by matching the compiler name in each configuration section
>> +# against a prefix of the command line. The problem is that, if the
>> +# compiler name and its initial flags stored in the libtool
>> +# configuration file don't match those in the command line, libtool
>> +# can't decide which configuration to use, and it gives up. The
>> +# correct solution is to add `--tag CXX' to LTCXXCOMPILE and maybe
>> +# CXXLINK, just after $(LIBTOOL), so that libtool doesn't have to
>> +# attempt to infer which configuration to use.
>> +#
>> +# The second tag argument, `--tag disable-shared` means that libtool
>> +# only compiles each source once, for static objects. In actuality,
>> +# glibcxx_lt_pic_flag and glibcxx_compiler_shared_flag are added to
>> +# the libtool command that is used create the object, which is
>> +# suitable for shared libraries. The `--tag disable-shared` must be
>> +# placed after --tag CXX lest things CXX undo the affect of
>> +# disable-shared.
>> +
>> +# 2) Need to explicitly set LTCXXCOMPILE so that EXTRA_CXX_FLAGS is
>> +# last. (That way, things like -O2 passed down from the toplevel can
>> +# be overridden by --enable-debug.)
>> +LTCXXCOMPILE = \
>> + $(LIBTOOL) --tag CXX --tag disable-shared \
>> + $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
>> + --mode=compile $(CXX) $(TOPLEVEL_INCLUDES) \
>> + $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS)
>> $(EXTRA_CXX_FLAGS)
>> +
>> +LTLDFLAGS = $(shell $(SHELL) $(top_srcdir)/../libtool-ldflags
>> $(LDFLAGS))
>> +
>> +# 3) We'd have a problem when building the shared libstdc++ object if
>> +# the rules automake generates would be used. We cannot allow g++ to
>> +# be used since this would add -lstdc++ to the link line which of
>> +# course is problematic at this point. So, we get the top-level
>> +# directory to configure libstdc++-v3 to use gcc as the C++
>> +# compilation driver.
>> +CXXLINK = \
>> + $(LIBTOOL) --tag CXX --tag disable-shared \
>> + $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
>> + --mode=link $(CXX) \
>> + $(VTV_CXXLINKFLAGS) \
>> + $(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@
>> diff --git a/libstdc++-v3/include/experimental/contract
>> b/libstdc++-v3/include/experimental/contract
>> new file mode 100644
>> index 00000000000..16f3fd5fd5a
>> --- /dev/null
>> +++ b/libstdc++-v3/include/experimental/contract
>> @@ -0,0 +1,82 @@
>> +// Contracts support header for -*- C++ -*-
>> +
>> +// Copyright (C) 1995-2022 Free Software Foundation, Inc.
>
> Just 2022 again (or earlier if this is based on Lock3 code contributed
> earilier? but not 1995 I think!)
>
>> +// This file is part of GCC.
>> +//
>> +// GCC is free software; you can redistribute it and/or modify
>> +// it under the terms of the GNU General Public License as published by
>> +// the Free Software Foundation; either version 3, or (at your option)
>> +// any later version.
>> +//
>> +// GCC is distributed in the hope that it will be useful,
>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> +// GNU General Public License for more details.
>> +//
>> +// Under Section 7 of GPL version 3, you are granted additional
>> +// permissions described in the GCC Runtime Library Exception, version
>> +// 3.1, as published by the Free Software Foundation.
>> +
>> +// You should have received a copy of the GNU General Public License and
>> +// a copy of the GCC Runtime Library Exception along with this program;
>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
>> +// <http://www.gnu.org/licenses/>.
>> +
>> +/** @file contract
>> + * This is a Standard C++ Library header.
>> + */
>> +
>> +#ifndef _GLIBCXX_CONTRACT
>> +#define _GLIBCXX_CONTRACT 1
>> +
>> +#pragma GCC system_header
>> +
>> +#if __cplusplus >= 201703L
>> +
>> +#include <bits/c++config.h>
>
> This is included by <string_view> so not needed here.
>
> OK for trunk with those tweaks, thanks.
Thanks, this is what I'm pushing:
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From db34b4a065e2876d58ff4e0040bfcf55396277a9 Mon Sep 17 00:00:00 2001
From: Jeff Chapman II <jchapman@lock3software.com>
Date: Thu, 3 Nov 2022 15:47:19 -0400
Subject: [PATCH] libstdc++: add experimental Contracts support
To: gcc-patches@gcc.gnu.org
This patch adds the library support for the experimental C++ Contracts
implementation. This now consists only of a default definition of the
violation handler, which users can override through defining their own
version. To avoid ABI stability problems with libstdc++.so this is added to
a separate -lstdc++exp static library, which the driver knows to add when it
sees -fcontracts.
Co-authored-by: Andrew Marmaduke <amarmaduke@lock3software.com>
Co-authored-by: Jason Merrill <jason@redhat.com>
libstdc++-v3/ChangeLog:
* acinclude.m4 (glibcxx_SUBDIRS): Add src/experimental.
* include/Makefile.am (experimental_headers): Add contract.
* include/Makefile.in: Regenerate.
* src/Makefile.am (SUBDIRS): Add experimental.
* src/Makefile.in: Regenerate.
* configure: Regenerate.
* src/experimental/contract.cc: New file.
* src/experimental/Makefile.am: New file.
* src/experimental/Makefile.in: New file.
* include/experimental/contract: New file.
---
libstdc++-v3/src/experimental/contract.cc | 41 +++++++++
libstdc++-v3/acinclude.m4 | 2 +-
libstdc++-v3/include/Makefile.am | 1 +
libstdc++-v3/src/Makefile.am | 3 +-
libstdc++-v3/src/experimental/Makefile.am | 96 ++++++++++++++++++++++
libstdc++-v3/include/experimental/contract | 81 ++++++++++++++++++
6 files changed, 222 insertions(+), 2 deletions(-)
create mode 100644 libstdc++-v3/src/experimental/contract.cc
create mode 100644 libstdc++-v3/src/experimental/Makefile.am
create mode 100644 libstdc++-v3/include/experimental/contract
diff --git a/libstdc++-v3/src/experimental/contract.cc b/libstdc++-v3/src/experimental/contract.cc
new file mode 100644
index 00000000000..c8d2697eddc
--- /dev/null
+++ b/libstdc++-v3/src/experimental/contract.cc
@@ -0,0 +1,41 @@
+// -*- C++ -*- std::experimental::contract_violation and friends
+// Copyright (C) 2019-2022 Free Software Foundation, Inc.
+//
+// This file is part of GCC.
+//
+// GCC is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// GCC is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+#include <experimental/contract>
+#include <iostream>
+
+__attribute__ ((weak)) void
+handle_contract_violation (const std::experimental::contract_violation &violation)
+{
+ std::cerr << "default std::handle_contract_violation called: \n"
+ << " " << violation.file_name()
+ << " " << violation.line_number()
+ << " " << violation.function_name()
+ << " " << violation.comment()
+ << " " << violation.assertion_level()
+ << " " << violation.assertion_role()
+ << " " << (int)violation.continuation_mode()
+ << std::endl;
+}
+
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 6f672924a73..baf01913a90 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -49,7 +49,7 @@ AC_DEFUN([GLIBCXX_CONFIGURE], [
# Keep these sync'd with the list in Makefile.am. The first provides an
# expandable list at autoconf time; the second provides an expandable list
# (i.e., shell variable) at configure time.
- m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/c++20 src/filesystem src/libbacktrace doc po testsuite python])
+ m4_define([glibcxx_SUBDIRS],[include libsupc++ src src/c++98 src/c++11 src/c++17 src/c++20 src/filesystem src/libbacktrace src/experimental doc po testsuite python])
SUBDIRS='glibcxx_SUBDIRS'
# These need to be absolute paths, yet at the same time need to
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 27dfa2be2f3..92b5450fc14 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -770,6 +770,7 @@ experimental_headers = \
${experimental_srcdir}/array \
${experimental_srcdir}/buffer \
${experimental_srcdir}/chrono \
+ ${experimental_srcdir}/contract \
${experimental_srcdir}/deque \
${experimental_srcdir}/executor \
${experimental_srcdir}/forward_list \
diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
index 59d992a091c..38943f36fb4 100644
--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -35,7 +35,7 @@ backtrace_dir =
endif
## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.
-SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir) $(backtrace_dir)
+SUBDIRS = c++98 c++11 c++17 c++20 $(filesystem_dir) $(backtrace_dir) experimental
# Cross compiler support.
if VTV_CYGMIN
@@ -73,6 +73,7 @@ endif
if ENABLE_BACKTRACE
vpath % $(top_srcdir)/src/libbacktrace
endif
+vpath % $(top_srcdir)/src/experimental
if GLIBCXX_LDBL_COMPAT
ldbl_compat_sources = compatibility-ldbl.cc
diff --git a/libstdc++-v3/src/experimental/Makefile.am b/libstdc++-v3/src/experimental/Makefile.am
new file mode 100644
index 00000000000..66f4532c707
--- /dev/null
+++ b/libstdc++-v3/src/experimental/Makefile.am
@@ -0,0 +1,96 @@
+## Makefile for experimental additions to the GNU C++ Standard library.
+##
+## Copyright (C) 2014-2022 Free Software Foundation, Inc.
+##
+## Process this file with automake to produce Makefile.in.
+##
+## This file is part of GCC.
+##
+## GCC is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3, or (at your option)
+## any later version.
+##
+## GCC is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with GCC; see the file COPYING3. If not see
+## <http://www.gnu.org/licenses/>.
+
+include $(top_srcdir)/fragment.am
+
+toolexeclib_LTLIBRARIES = libstdc++exp.la
+
+headers =
+
+sources = \
+ contract.cc
+
+# vpath % $(top_srcdir)/src/experimental
+
+libstdc__exp_la_SOURCES = $(sources)
+
+# AM_CXXFLAGS needs to be in each subdirectory so that it can be
+# modified in a per-library or per-sub-library way. Need to manually
+# set this option because CONFIG_CXXFLAGS has to be after
+# OPTIMIZE_CXXFLAGS on the compile line so that -O2 can be overridden
+# as the occasion calls for it.
+AM_CXXFLAGS = \
+ -std=gnu++17 -nostdinc++ \
+ $(glibcxx_lt_pic_flag) $(glibcxx_compiler_shared_flag) \
+ $(XTEMPLATE_FLAGS) $(VTV_CXXFLAGS) \
+ $(WARN_CXXFLAGS) $(OPTIMIZE_CXXFLAGS) $(CONFIG_CXXFLAGS) \
+ -fimplicit-templates
+
+AM_MAKEFLAGS = \
+ "gxx_include_dir=$(gxx_include_dir)"
+
+# Libtool notes
+
+# 1) In general, libtool expects an argument such as `--tag=CXX' when
+# using the C++ compiler, because that will enable the settings
+# detected when C++ support was being configured. However, when no
+# such flag is given in the command line, libtool attempts to figure
+# it out by matching the compiler name in each configuration section
+# against a prefix of the command line. The problem is that, if the
+# compiler name and its initial flags stored in the libtool
+# configuration file don't match those in the command line, libtool
+# can't decide which configuration to use, and it gives up. The
+# correct solution is to add `--tag CXX' to LTCXXCOMPILE and maybe
+# CXXLINK, just after $(LIBTOOL), so that libtool doesn't have to
+# attempt to infer which configuration to use.
+#
+# The second tag argument, `--tag disable-shared` means that libtool
+# only compiles each source once, for static objects. In actuality,
+# glibcxx_lt_pic_flag and glibcxx_compiler_shared_flag are added to
+# the libtool command that is used create the object, which is
+# suitable for shared libraries. The `--tag disable-shared` must be
+# placed after --tag CXX lest things CXX undo the affect of
+# disable-shared.
+
+# 2) Need to explicitly set LTCXXCOMPILE so that EXTRA_CXX_FLAGS is
+# last. (That way, things like -O2 passed down from the toplevel can
+# be overridden by --enable-debug.)
+LTCXXCOMPILE = \
+ $(LIBTOOL) --tag CXX --tag disable-shared \
+ $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+ --mode=compile $(CXX) $(TOPLEVEL_INCLUDES) \
+ $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) $(EXTRA_CXX_FLAGS)
+
+LTLDFLAGS = $(shell $(SHELL) $(top_srcdir)/../libtool-ldflags $(LDFLAGS))
+
+# 3) We'd have a problem when building the shared libstdc++ object if
+# the rules automake generates would be used. We cannot allow g++ to
+# be used since this would add -lstdc++ to the link line which of
+# course is problematic at this point. So, we get the top-level
+# directory to configure libstdc++-v3 to use gcc as the C++
+# compilation driver.
+CXXLINK = \
+ $(LIBTOOL) --tag CXX --tag disable-shared \
+ $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+ --mode=link $(CXX) \
+ $(VTV_CXXLINKFLAGS) \
+ $(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@
diff --git a/libstdc++-v3/include/experimental/contract b/libstdc++-v3/include/experimental/contract
new file mode 100644
index 00000000000..cf655023da7
--- /dev/null
+++ b/libstdc++-v3/include/experimental/contract
@@ -0,0 +1,81 @@
+// Contracts support header for -*- C++ -*-
+
+// Copyright (C) 2019-2022 Free Software Foundation, Inc.
+//
+// This file is part of GCC.
+//
+// GCC is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3, or (at your option)
+// any later version.
+//
+// GCC is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file contract
+ * This is a Standard C++ Library header.
+ */
+
+#ifndef _GLIBCXX_CONTRACT
+#define _GLIBCXX_CONTRACT 1
+
+#pragma GCC system_header
+
+#if __cplusplus >= 201703L
+
+#include <string_view>
+#include <cstdint>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+namespace experimental
+{
+ // From P1332
+ enum class contract_violation_continuation_mode {
+ NEVER_CONTINUE, MAYBE_CONTINUE
+ };
+
+ class contract_violation {
+ const char* _M_file;
+ const char* _M_function;
+ const char* _M_comment;
+ const char* _M_level;
+ const char* _M_role;
+ uint_least32_t _M_line;
+ signed char _M_continue;
+ public:
+ // From N4820
+ uint_least32_t line_number() const noexcept { return _M_line; }
+ string_view file_name() const noexcept { return _M_file; }
+ string_view function_name() const noexcept { return _M_function; }
+ string_view comment() const noexcept { return _M_comment; }
+ string_view assertion_level() const noexcept { return _M_level; }
+ // From P1332
+ string_view assertion_role() const noexcept { return _M_role; }
+ contract_violation_continuation_mode continuation_mode() const noexcept
+ { return static_cast<contract_violation_continuation_mode>(_M_continue); }
+ };
+
+} // namespace experimental
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+
+// To override the contract violation handler, define
+//void ::handle_contract_violation (const std::experimental::contract_violation &);
+
+#endif // C++17
+#endif // _GLIBCXX_CONTRACT
--
2.31.1
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