[PATCH RFA] libstdc++: add experimental Contracts support

[Jason Merrill <jason@redhat.com>]

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

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.
+//
+// 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
+    << " " << 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 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.
+//
+// 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>
+#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

base-commit: a4cd2389276a30c39034a83d640ce68fa407bac1
prerequisite-patch-id: 329bc16a88dc9a3b13cd3fcecb3678826cc592dc
-- 
2.31.1