[ovs-dev] [PATCH 4/5] Automatically verify that OVS header files work OK in C++ also.
Ben Pfaff
blp at ovn.org
Mon Jul 31 20:33:57 UTC 2017
On Mon, Jul 31, 2017 at 01:05:32PM -0700, Ben Pfaff wrote:
> On Mon, Jul 31, 2017 at 03:50:59PM -0400, Russell Bryant wrote:
> > On Sun, Jul 30, 2017 at 10:54 PM, Ben Pfaff <blp at ovn.org> wrote:
> > > This should help address a recurring problem.
> > >
> > > Signed-off-by: Ben Pfaff <blp at ovn.org>
> > > ---
> > > .travis.yml | 1 +
> > > Makefile.am | 1 +
> > > configure.ac | 2 ++
> > > include/openvswitch/automake.mk | 14 ++++++++++++++
> > > m4/openvswitch.m4 | 21 +++++++++++++++++++++
> > > 5 files changed, 39 insertions(+)
> >
> > Why does this patch depend on libboost? It looks like it's only used
> > when building a test C++ program in configure. We could build a test
> > C++ program without the dependency, right?
>
> It's because of include/openvswitch/compiler.h, which has:
>
> #elif defined(__cplusplus)
> #include <boost/static_assert.hpp>
> #define BUILD_ASSERT BOOST_STATIC_ASSERT
> #define BUILD_ASSERT_DECL BOOST_STATIC_ASSERT
>
> We could probably define our own C++-compatible static assert without
> boost. It looks like C++11 and later has a built-in static_assert:
> http://en.cppreference.com/w/cpp/language/static_assert
>
> Any idea whether it's reasonable to assume C++11 support these days?
Here's a version of the patch that gets rid of the boost dependency. It
adds a C++11 dependency instead.
--8<--------------------------cut here-------------------------->8--
From: Ben Pfaff <blp at ovn.org>
Date: Mon, 31 Jul 2017 13:31:43 -0700
Subject: [PATCH] Automatically verify that OVS header files work OK in C++
also.
This should help address a recurring problem.
Signed-off-by: Ben Pfaff <blp at ovn.org>
---
Makefile.am | 1 +
configure.ac | 2 +
include/openflow/openflow-common.h | 3 +-
include/openvswitch/automake.mk | 14 +
include/openvswitch/compiler.h | 5 +-
m4/ax_cxx_compile_stdcxx.m4 | 982 +++++++++++++++++++++++++++++++++++++
m4/openvswitch.m4 | 16 +
7 files changed, 1018 insertions(+), 5 deletions(-)
create mode 100644 m4/ax_cxx_compile_stdcxx.m4
diff --git a/Makefile.am b/Makefile.am
index 9679379defef..373ef6e9189f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -108,6 +108,7 @@ MAN_ROOTS =
noinst_DATA =
noinst_HEADERS =
lib_LTLIBRARIES =
+noinst_LTLIBRARIES =
noinst_man_MANS =
noinst_PROGRAMS =
noinst_SCRIPTS =
diff --git a/configure.ac b/configure.ac
index 194c4b92ee34..093b6ffed50e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,7 @@ AM_INIT_AUTOMAKE([tar-pax])
AC_PROG_CC_C99
AM_PROG_CC_C_O
+AC_PROG_CXX
AC_PROG_CPP
AC_PROG_MKDIR_P
AC_PROG_FGREP
@@ -135,6 +136,7 @@ OVS_CHECK_POSIX_AIO
OVS_CHECK_PTHREAD_SET_NAME
OVS_CHECK_LINUX_HOST
OVS_LIBTOOL_VERSIONS
+OVS_CHECK_CXX
AX_FUNC_POSIX_MEMALIGN
OVS_CHECK_INCLUDE_NEXT([stdio.h string.h])
diff --git a/include/openflow/openflow-common.h b/include/openflow/openflow-common.h
index 410f392d20cd..5f1e22589ced 100644
--- a/include/openflow/openflow-common.h
+++ b/include/openflow/openflow-common.h
@@ -60,8 +60,7 @@
extern int (*build_assert(void))[ sizeof(struct { \
unsigned int build_assert_failed : (EXPR) ? 1 : -1; })]
#else /* __cplusplus */
-#include <boost/static_assert.hpp>
-#define OFP_ASSERT BOOST_STATIC_ASSERT
+#define OFP_ASSERT(EXPR) static_assert(EXPR, "assertion failed")
#endif /* __cplusplus */
/* Version number:
diff --git a/include/openvswitch/automake.mk b/include/openvswitch/automake.mk
index 699d9d74ecd0..74b31acfa66b 100644
--- a/include/openvswitch/automake.mk
+++ b/include/openvswitch/automake.mk
@@ -30,3 +30,17 @@ openvswitchinclude_HEADERS = \
include/openvswitch/version.h \
include/openvswitch/vconn.h \
include/openvswitch/vlog.h
+
+if HAVE_CXX
+# OVS does not use C++ itself, but it provides public header files
+# that a C++ compiler should accept, so when --enable-Werror is in
+# effect and a C++ compiler is available, we build a C++ source file
+# that #includes all the public headers, as a way to ensure that they
+# are acceptable as C++.
+noinst_LTLIBRARIES += include/openvswitch/libcxxtest.la
+nodist_include_openvswitch_libcxxtest_la_SOURCES = include/openvswitch/cxxtest.cc
+include/openvswitch/cxxtest.cc: include/openvswitch/automake.mk
+ $(AM_V_GEN)for header in $(openvswitchinclude_HEADERS); do \
+ echo $$header; \
+ done | sed 's,^include/\(.*\)$$,#include <\1>,' > $@
+endif
diff --git a/include/openvswitch/compiler.h b/include/openvswitch/compiler.h
index 0dc8636add33..0076ad763578 100644
--- a/include/openvswitch/compiler.h
+++ b/include/openvswitch/compiler.h
@@ -244,9 +244,8 @@
#define BUILD_ASSERT(EXPR) ((void) 0)
#define BUILD_ASSERT_DECL(EXPR) extern int (*build_assert(void))[1]
#elif defined(__cplusplus)
-#include <boost/static_assert.hpp>
-#define BUILD_ASSERT BOOST_STATIC_ASSERT
-#define BUILD_ASSERT_DECL BOOST_STATIC_ASSERT
+#define BUILD_ASSERT(EXPR) static_assert(EXPR, "assertion failed")
+#define BUILD_ASSERT_DECL(EXPR) static_assert(EXPR, "assertion failed")
#elif (__GNUC__ * 256 + __GNUC_MINOR__ >= 0x403 \
|| __has_extension(c_static_assert))
#define BUILD_ASSERT_DECL(EXPR) _Static_assert(EXPR, #EXPR)
diff --git a/m4/ax_cxx_compile_stdcxx.m4 b/m4/ax_cxx_compile_stdcxx.m4
new file mode 100644
index 000000000000..5032bba8091d
--- /dev/null
+++ b/m4/ax_cxx_compile_stdcxx.m4
@@ -0,0 +1,982 @@
+# ===========================================================================
+# https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+# AX_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional])
+#
+# DESCRIPTION
+#
+# Check for baseline language coverage in the compiler for the specified
+# version of the C++ standard. If necessary, add switches to CXX and
+# CXXCPP to enable support. VERSION may be '11' (for the C++11 standard)
+# or '14' (for the C++14 standard).
+#
+# The second argument, if specified, indicates whether you insist on an
+# extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
+# -std=c++11). If neither is specified, you get whatever works, with
+# preference for an extended mode.
+#
+# The third argument, if specified 'mandatory' or if left unspecified,
+# indicates that baseline support for the specified C++ standard is
+# required and that the macro should error out if no mode with that
+# support is found. If specified 'optional', then configuration proceeds
+# regardless, after defining HAVE_CXX${VERSION} if and only if a
+# supporting mode is found.
+#
+# LICENSE
+#
+# Copyright (c) 2008 Benjamin Kosnik <bkoz at redhat.com>
+# Copyright (c) 2012 Zack Weinberg <zackw at panix.com>
+# Copyright (c) 2013 Roy Stogner <roystgnr at ices.utexas.edu>
+# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov at google.com>
+# Copyright (c) 2015 Paul Norman <penorman at mac.com>
+# Copyright (c) 2015 Moritz Klammler <moritz at klammler.eu>
+# Copyright (c) 2016 Krzesimir Nowak <qdlacz at gmail.com>
+#
+# Copying and distribution of this file, with or without modification, are
+# permitted in any medium without royalty provided the copyright notice
+# and this notice are preserved. This file is offered as-is, without any
+# warranty.
+
+#serial 7
+
+dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
+dnl (serial version number 13).
+
+AX_REQUIRE_DEFINED([AC_MSG_WARN])
+AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
+ m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
+ [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
+ [$1], [17], [ax_cxx_compile_alternatives="17 1z"],
+ [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
+ m4_if([$2], [], [],
+ [$2], [ext], [],
+ [$2], [noext], [],
+ [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
+ m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
+ [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
+ [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
+ [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
+ AC_LANG_PUSH([C++])dnl
+ ac_success=no
+ AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
+ ax_cv_cxx_compile_cxx$1,
+ [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+ [ax_cv_cxx_compile_cxx$1=yes],
+ [ax_cv_cxx_compile_cxx$1=no])])
+ if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
+ ac_success=yes
+ fi
+
+ m4_if([$2], [noext], [], [dnl
+ if test x$ac_success = xno; then
+ for alternative in ${ax_cxx_compile_alternatives}; do
+ switch="-std=gnu++${alternative}"
+ cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
+ AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+ $cachevar,
+ [ac_save_CXX="$CXX"
+ CXX="$CXX $switch"
+ AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+ [eval $cachevar=yes],
+ [eval $cachevar=no])
+ CXX="$ac_save_CXX"])
+ if eval test x\$$cachevar = xyes; then
+ CXX="$CXX $switch"
+ if test -n "$CXXCPP" ; then
+ CXXCPP="$CXXCPP $switch"
+ fi
+ ac_success=yes
+ break
+ fi
+ done
+ fi])
+
+ m4_if([$2], [ext], [], [dnl
+ if test x$ac_success = xno; then
+ dnl HP's aCC needs +std=c++11 according to:
+ dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
+ dnl Cray's crayCC needs "-h std=c++11"
+ for alternative in ${ax_cxx_compile_alternatives}; do
+ for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
+ cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
+ AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+ $cachevar,
+ [ac_save_CXX="$CXX"
+ CXX="$CXX $switch"
+ AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+ [eval $cachevar=yes],
+ [eval $cachevar=no])
+ CXX="$ac_save_CXX"])
+ if eval test x\$$cachevar = xyes; then
+ CXX="$CXX $switch"
+ if test -n "$CXXCPP" ; then
+ CXXCPP="$CXXCPP $switch"
+ fi
+ ac_success=yes
+ break
+ fi
+ done
+ if test x$ac_success = xyes; then
+ break
+ fi
+ done
+ fi])
+ AC_LANG_POP([C++])
+ if test x$ax_cxx_compile_cxx$1_required = xtrue; then
+ if test x$ac_success = xno; then
+ AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
+ fi
+ fi
+ if test x$ac_success = xno; then
+ HAVE_CXX$1=0
+ AC_MSG_NOTICE([No compiler with C++$1 support was found])
+ else
+ HAVE_CXX$1=1
+ AC_DEFINE(HAVE_CXX$1,1,
+ [define if the compiler supports basic C++$1 syntax])
+ fi
+ AC_SUBST(HAVE_CXX$1)
+ m4_if([$1], [17], [AC_MSG_WARN([C++17 is not yet standardized, so the checks may change in incompatible ways anytime])])
+])
+
+
+dnl Test body for checking C++11 support
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+)
+
+
+dnl Test body for checking C++14 support
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
+)
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_17],
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
+ _AX_CXX_COMPILE_STDCXX_testbody_new_in_17
+)
+
+dnl Tests for new features in C++11
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
+
+// If the compiler admits that it is not ready for C++11, why torture it?
+// Hopefully, this will speed up the test.
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201103L
+
+#error "This is not a C++11 compiler"
+
+#else
+
+namespace cxx11
+{
+
+ namespace test_static_assert
+ {
+
+ template <typename T>
+ struct check
+ {
+ static_assert(sizeof(int) <= sizeof(T), "not big enough");
+ };
+
+ }
+
+ namespace test_final_override
+ {
+
+ struct Base
+ {
+ virtual void f() {}
+ };
+
+ struct Derived : public Base
+ {
+ virtual void f() override {}
+ };
+
+ }
+
+ namespace test_double_right_angle_brackets
+ {
+
+ template < typename T >
+ struct check {};
+
+ typedef check<void> single_type;
+ typedef check<check<void>> double_type;
+ typedef check<check<check<void>>> triple_type;
+ typedef check<check<check<check<void>>>> quadruple_type;
+
+ }
+
+ namespace test_decltype
+ {
+
+ int
+ f()
+ {
+ int a = 1;
+ decltype(a) b = 2;
+ return a + b;
+ }
+
+ }
+
+ namespace test_type_deduction
+ {
+
+ template < typename T1, typename T2 >
+ struct is_same
+ {
+ static const bool value = false;
+ };
+
+ template < typename T >
+ struct is_same<T, T>
+ {
+ static const bool value = true;
+ };
+
+ template < typename T1, typename T2 >
+ auto
+ add(T1 a1, T2 a2) -> decltype(a1 + a2)
+ {
+ return a1 + a2;
+ }
+
+ int
+ test(const int c, volatile int v)
+ {
+ static_assert(is_same<int, decltype(0)>::value == true, "");
+ static_assert(is_same<int, decltype(c)>::value == false, "");
+ static_assert(is_same<int, decltype(v)>::value == false, "");
+ auto ac = c;
+ auto av = v;
+ auto sumi = ac + av + 'x';
+ auto sumf = ac + av + 1.0;
+ static_assert(is_same<int, decltype(ac)>::value == true, "");
+ static_assert(is_same<int, decltype(av)>::value == true, "");
+ static_assert(is_same<int, decltype(sumi)>::value == true, "");
+ static_assert(is_same<int, decltype(sumf)>::value == false, "");
+ static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
+ return (sumf > 0.0) ? sumi : add(c, v);
+ }
+
+ }
+
+ namespace test_noexcept
+ {
+
+ int f() { return 0; }
+ int g() noexcept { return 0; }
+
+ static_assert(noexcept(f()) == false, "");
+ static_assert(noexcept(g()) == true, "");
+
+ }
+
+ namespace test_constexpr
+ {
+
+ template < typename CharT >
+ unsigned long constexpr
+ strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
+ {
+ return *s ? strlen_c_r(s + 1, acc + 1) : acc;
+ }
+
+ template < typename CharT >
+ unsigned long constexpr
+ strlen_c(const CharT *const s) noexcept
+ {
+ return strlen_c_r(s, 0UL);
+ }
+
+ static_assert(strlen_c("") == 0UL, "");
+ static_assert(strlen_c("1") == 1UL, "");
+ static_assert(strlen_c("example") == 7UL, "");
+ static_assert(strlen_c("another\0example") == 7UL, "");
+
+ }
+
+ namespace test_rvalue_references
+ {
+
+ template < int N >
+ struct answer
+ {
+ static constexpr int value = N;
+ };
+
+ answer<1> f(int&) { return answer<1>(); }
+ answer<2> f(const int&) { return answer<2>(); }
+ answer<3> f(int&&) { return answer<3>(); }
+
+ void
+ test()
+ {
+ int i = 0;
+ const int c = 0;
+ static_assert(decltype(f(i))::value == 1, "");
+ static_assert(decltype(f(c))::value == 2, "");
+ static_assert(decltype(f(0))::value == 3, "");
+ }
+
+ }
+
+ namespace test_uniform_initialization
+ {
+
+ struct test
+ {
+ static const int zero {};
+ static const int one {1};
+ };
+
+ static_assert(test::zero == 0, "");
+ static_assert(test::one == 1, "");
+
+ }
+
+ namespace test_lambdas
+ {
+
+ void
+ test1()
+ {
+ auto lambda1 = [](){};
+ auto lambda2 = lambda1;
+ lambda1();
+ lambda2();
+ }
+
+ int
+ test2()
+ {
+ auto a = [](int i, int j){ return i + j; }(1, 2);
+ auto b = []() -> int { return '0'; }();
+ auto c = [=](){ return a + b; }();
+ auto d = [&](){ return c; }();
+ auto e = [a, &b](int x) mutable {
+ const auto identity = [](int y){ return y; };
+ for (auto i = 0; i < a; ++i)
+ a += b--;
+ return x + identity(a + b);
+ }(0);
+ return a + b + c + d + e;
+ }
+
+ int
+ test3()
+ {
+ const auto nullary = [](){ return 0; };
+ const auto unary = [](int x){ return x; };
+ using nullary_t = decltype(nullary);
+ using unary_t = decltype(unary);
+ const auto higher1st = [](nullary_t f){ return f(); };
+ const auto higher2nd = [unary](nullary_t f1){
+ return [unary, f1](unary_t f2){ return f2(unary(f1())); };
+ };
+ return higher1st(nullary) + higher2nd(nullary)(unary);
+ }
+
+ }
+
+ namespace test_variadic_templates
+ {
+
+ template <int...>
+ struct sum;
+
+ template <int N0, int... N1toN>
+ struct sum<N0, N1toN...>
+ {
+ static constexpr auto value = N0 + sum<N1toN...>::value;
+ };
+
+ template <>
+ struct sum<>
+ {
+ static constexpr auto value = 0;
+ };
+
+ static_assert(sum<>::value == 0, "");
+ static_assert(sum<1>::value == 1, "");
+ static_assert(sum<23>::value == 23, "");
+ static_assert(sum<1, 2>::value == 3, "");
+ static_assert(sum<5, 5, 11>::value == 21, "");
+ static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
+
+ }
+
+ // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
+ // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
+ // because of this.
+ namespace test_template_alias_sfinae
+ {
+
+ struct foo {};
+
+ template<typename T>
+ using member = typename T::member_type;
+
+ template<typename T>
+ void func(...) {}
+
+ template<typename T>
+ void func(member<T>*) {}
+
+ void test();
+
+ void test() { func<foo>(0); }
+
+ }
+
+} // namespace cxx11
+
+#endif // __cplusplus >= 201103L
+
+]])
+
+
+dnl Tests for new features in C++14
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
+
+// If the compiler admits that it is not ready for C++14, why torture it?
+// Hopefully, this will speed up the test.
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201402L
+
+#error "This is not a C++14 compiler"
+
+#else
+
+namespace cxx14
+{
+
+ namespace test_polymorphic_lambdas
+ {
+
+ int
+ test()
+ {
+ const auto lambda = [](auto&&... args){
+ const auto istiny = [](auto x){
+ return (sizeof(x) == 1UL) ? 1 : 0;
+ };
+ const int aretiny[] = { istiny(args)... };
+ return aretiny[0];
+ };
+ return lambda(1, 1L, 1.0f, '1');
+ }
+
+ }
+
+ namespace test_binary_literals
+ {
+
+ constexpr auto ivii = 0b0000000000101010;
+ static_assert(ivii == 42, "wrong value");
+
+ }
+
+ namespace test_generalized_constexpr
+ {
+
+ template < typename CharT >
+ constexpr unsigned long
+ strlen_c(const CharT *const s) noexcept
+ {
+ auto length = 0UL;
+ for (auto p = s; *p; ++p)
+ ++length;
+ return length;
+ }
+
+ static_assert(strlen_c("") == 0UL, "");
+ static_assert(strlen_c("x") == 1UL, "");
+ static_assert(strlen_c("test") == 4UL, "");
+ static_assert(strlen_c("another\0test") == 7UL, "");
+
+ }
+
+ namespace test_lambda_init_capture
+ {
+
+ int
+ test()
+ {
+ auto x = 0;
+ const auto lambda1 = [a = x](int b){ return a + b; };
+ const auto lambda2 = [a = lambda1(x)](){ return a; };
+ return lambda2();
+ }
+
+ }
+
+ namespace test_digit_separators
+ {
+
+ constexpr auto ten_million = 100'000'000;
+ static_assert(ten_million == 100000000, "");
+
+ }
+
+ namespace test_return_type_deduction
+ {
+
+ auto f(int& x) { return x; }
+ decltype(auto) g(int& x) { return x; }
+
+ template < typename T1, typename T2 >
+ struct is_same
+ {
+ static constexpr auto value = false;
+ };
+
+ template < typename T >
+ struct is_same<T, T>
+ {
+ static constexpr auto value = true;
+ };
+
+ int
+ test()
+ {
+ auto x = 0;
+ static_assert(is_same<int, decltype(f(x))>::value, "");
+ static_assert(is_same<int&, decltype(g(x))>::value, "");
+ return x;
+ }
+
+ }
+
+} // namespace cxx14
+
+#endif // __cplusplus >= 201402L
+
+]])
+
+
+dnl Tests for new features in C++17
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
+
+// If the compiler admits that it is not ready for C++17, why torture it?
+// Hopefully, this will speed up the test.
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus <= 201402L
+
+#error "This is not a C++17 compiler"
+
+#else
+
+#if defined(__clang__)
+ #define REALLY_CLANG
+#else
+ #if defined(__GNUC__)
+ #define REALLY_GCC
+ #endif
+#endif
+
+#include <initializer_list>
+#include <utility>
+#include <type_traits>
+
+namespace cxx17
+{
+
+#if !defined(REALLY_CLANG)
+ namespace test_constexpr_lambdas
+ {
+
+ // TODO: test it with clang++ from git
+
+ constexpr int foo = [](){return 42;}();
+
+ }
+#endif // !defined(REALLY_CLANG)
+
+ namespace test::nested_namespace::definitions
+ {
+
+ }
+
+ namespace test_fold_expression
+ {
+
+ template<typename... Args>
+ int multiply(Args... args)
+ {
+ return (args * ... * 1);
+ }
+
+ template<typename... Args>
+ bool all(Args... args)
+ {
+ return (args && ...);
+ }
+
+ }
+
+ namespace test_extended_static_assert
+ {
+
+ static_assert (true);
+
+ }
+
+ namespace test_auto_brace_init_list
+ {
+
+ auto foo = {5};
+ auto bar {5};
+
+ static_assert(std::is_same<std::initializer_list<int>, decltype(foo)>::value);
+ static_assert(std::is_same<int, decltype(bar)>::value);
+ }
+
+ namespace test_typename_in_template_template_parameter
+ {
+
+ template<template<typename> typename X> struct D;
+
+ }
+
+ namespace test_fallthrough_nodiscard_maybe_unused_attributes
+ {
+
+ int f1()
+ {
+ return 42;
+ }
+
+ [[nodiscard]] int f2()
+ {
+ [[maybe_unused]] auto unused = f1();
+
+ switch (f1())
+ {
+ case 17:
+ f1();
+ [[fallthrough]];
+ case 42:
+ f1();
+ }
+ return f1();
+ }
+
+ }
+
+ namespace test_extended_aggregate_initialization
+ {
+
+ struct base1
+ {
+ int b1, b2 = 42;
+ };
+
+ struct base2
+ {
+ base2() {
+ b3 = 42;
+ }
+ int b3;
+ };
+
+ struct derived : base1, base2
+ {
+ int d;
+ };
+
+ derived d1 {{1, 2}, {}, 4}; // full initialization
+ derived d2 {{}, {}, 4}; // value-initialized bases
+
+ }
+
+ namespace test_general_range_based_for_loop
+ {
+
+ struct iter
+ {
+ int i;
+
+ int& operator* ()
+ {
+ return i;
+ }
+
+ const int& operator* () const
+ {
+ return i;
+ }
+
+ iter& operator++()
+ {
+ ++i;
+ return *this;
+ }
+ };
+
+ struct sentinel
+ {
+ int i;
+ };
+
+ bool operator== (const iter& i, const sentinel& s)
+ {
+ return i.i == s.i;
+ }
+
+ bool operator!= (const iter& i, const sentinel& s)
+ {
+ return !(i == s);
+ }
+
+ struct range
+ {
+ iter begin() const
+ {
+ return {0};
+ }
+
+ sentinel end() const
+ {
+ return {5};
+ }
+ };
+
+ void f()
+ {
+ range r {};
+
+ for (auto i : r)
+ {
+ [[maybe_unused]] auto v = i;
+ }
+ }
+
+ }
+
+ namespace test_lambda_capture_asterisk_this_by_value
+ {
+
+ struct t
+ {
+ int i;
+ int foo()
+ {
+ return [*this]()
+ {
+ return i;
+ }();
+ }
+ };
+
+ }
+
+ namespace test_enum_class_construction
+ {
+
+ enum class byte : unsigned char
+ {};
+
+ byte foo {42};
+
+ }
+
+ namespace test_constexpr_if
+ {
+
+ template <bool cond>
+ int f ()
+ {
+ if constexpr(cond)
+ {
+ return 13;
+ }
+ else
+ {
+ return 42;
+ }
+ }
+
+ }
+
+ namespace test_selection_statement_with_initializer
+ {
+
+ int f()
+ {
+ return 13;
+ }
+
+ int f2()
+ {
+ if (auto i = f(); i > 0)
+ {
+ return 3;
+ }
+
+ switch (auto i = f(); i + 4)
+ {
+ case 17:
+ return 2;
+
+ default:
+ return 1;
+ }
+ }
+
+ }
+
+#if !defined(REALLY_CLANG)
+ namespace test_template_argument_deduction_for_class_templates
+ {
+
+ // TODO: test it with clang++ from git
+
+ template <typename T1, typename T2>
+ struct pair
+ {
+ pair (T1 p1, T2 p2)
+ : m1 {p1},
+ m2 {p2}
+ {}
+
+ T1 m1;
+ T2 m2;
+ };
+
+ void f()
+ {
+ [[maybe_unused]] auto p = pair{13, 42u};
+ }
+
+ }
+#endif // !defined(REALLY_CLANG)
+
+ namespace test_non_type_auto_template_parameters
+ {
+
+ template <auto n>
+ struct B
+ {};
+
+ B<5> b1;
+ B<'a'> b2;
+
+ }
+
+#if !defined(REALLY_CLANG)
+ namespace test_structured_bindings
+ {
+
+ // TODO: test it with clang++ from git
+
+ int arr[2] = { 1, 2 };
+ std::pair<int, int> pr = { 1, 2 };
+
+ auto f1() -> int(&)[2]
+ {
+ return arr;
+ }
+
+ auto f2() -> std::pair<int, int>&
+ {
+ return pr;
+ }
+
+ struct S
+ {
+ int x1 : 2;
+ volatile double y1;
+ };
+
+ S f3()
+ {
+ return {};
+ }
+
+ auto [ x1, y1 ] = f1();
+ auto& [ xr1, yr1 ] = f1();
+ auto [ x2, y2 ] = f2();
+ auto& [ xr2, yr2 ] = f2();
+ const auto [ x3, y3 ] = f3();
+
+ }
+#endif // !defined(REALLY_CLANG)
+
+#if !defined(REALLY_CLANG)
+ namespace test_exception_spec_type_system
+ {
+
+ // TODO: test it with clang++ from git
+
+ struct Good {};
+ struct Bad {};
+
+ void g1() noexcept;
+ void g2();
+
+ template<typename T>
+ Bad
+ f(T*, T*);
+
+ template<typename T1, typename T2>
+ Good
+ f(T1*, T2*);
+
+ static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
+
+ }
+#endif // !defined(REALLY_CLANG)
+
+ namespace test_inline_variables
+ {
+
+ template<class T> void f(T)
+ {}
+
+ template<class T> inline T g(T)
+ {
+ return T{};
+ }
+
+ template<> inline void f<>(int)
+ {}
+
+ template<> int g<>(int)
+ {
+ return 5;
+ }
+
+ }
+
+} // namespace cxx17
+
+#endif // __cplusplus <= 201402L
+
+]])
diff --git a/m4/openvswitch.m4 b/m4/openvswitch.m4
index 648750ab5ad9..00ffad35f6b0 100644
--- a/m4/openvswitch.m4
+++ b/m4/openvswitch.m4
@@ -620,3 +620,19 @@ AC_DEFUN([OVS_LIBTOOL_VERSIONS],
AC_MSG_RESULT([libX-$OVS_MAJOR.$OVS_MINOR.so.$LT_CURRENT.0.$OVS_MICRO)])
AC_SUBST(OVS_LTINFO)
])
+
+dnl OVS does not use C++ itself, but it provides public header files
+dnl that a C++ compiler should accept, so when --enable-Werror is in
+dnl effect and a C++ compiler is available, we enable building a C++
+dnl source file that #includes all the public headers, as a way to
+dnl ensure that they are acceptable as C++.
+AC_DEFUN([OVS_CHECK_CXX],
+ [AC_REQUIRE([AC_PROG_CXX])
+ AC_REQUIRE([OVS_ENABLE_WERROR])
+ AX_CXX_COMPILE_STDCXX([11], [], [optional])
+ if test $enable_Werror = yes && test $HAVE_CXX11 = 1; then
+ enable_cxx=:
+ else
+ enable_cxx=false
+ fi
+ AM_CONDITIONAL([HAVE_CXX], [$enable_cxx])])
--
2.10.2
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