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[lmi-commits] [lmi] master 20496df 1/2: Use -std=c++17 flag in configure
|
From: |
Vadim Zeitlin |
|
Subject: |
[lmi-commits] [lmi] master 20496df 1/2: Use -std=c++17 flag in configure builds |
|
Date: |
Tue, 13 Feb 2018 17:57:45 -0500 (EST) |
branch: master
commit 20496df62a10e22868ae8cef8d9112caa21c50d5
Author: Vadim Zeitlin <address@hidden>
Commit: Vadim Zeitlin <address@hidden>
Use -std=c++17 flag in configure builds
This is now required to build lmi successfully with gcc as lmi uses at
least the "terse static assert" C++17 feature.
Also stop using AX_CXX_COMPILE_STDCXX macro from Autoconf archive as the
version we had was too old and didn't allow checking for C++17 support
at all, while the latest version of this macro is too new and its C++17
checks are too stringent to allow gcc 6, which can be used for building
lmi, to pass them (notably C++17 constexpr lambdas check fails). So just
use our own simple and naïve, but sufficient for our needs, C++17 check
instead.
---
aclocal/ax_cxx_compile_stdcxx.m4 | 558 ---------------------------------------
configure.ac | 28 +-
2 files changed, 27 insertions(+), 559 deletions(-)
diff --git a/aclocal/ax_cxx_compile_stdcxx.m4 b/aclocal/ax_cxx_compile_stdcxx.m4
deleted file mode 100644
index 079e17d..0000000
--- a/aclocal/ax_cxx_compile_stdcxx.m4
+++ /dev/null
@@ -1,558 +0,0 @@
-# ===========================================================================
-# http://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 CXXFLAGS 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 <address@hidden>
-# Copyright (c) 2012 Zack Weinberg <address@hidden>
-# Copyright (c) 2013 Roy Stogner <address@hidden>
-# Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov
<address@hidden>
-# Copyright (c) 2015 Paul Norman <address@hidden>
-# Copyright (c) 2015 Moritz Klammler <address@hidden>
-#
-# 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 1
-
-dnl This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
-dnl (serial version number 13).
-
-AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
- m4_if([$1], [11], [],
- [$1], [14], [],
- [$1], [17], [m4_fatal([support for C++17 not yet implemented in
AX_CXX_COMPILE_STDCXX])],
- [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 switch in -std=gnu++$1 -std=gnu++0x; do
- cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
- AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
- $cachevar,
- [ac_save_CXXFLAGS="$CXXFLAGS"
- CXXFLAGS="$CXXFLAGS $switch"
-
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
- [eval $cachevar=yes],
- [eval $cachevar=no])
- CXXFLAGS="$ac_save_CXXFLAGS"])
- if eval test x\$$cachevar = xyes; then
- CXXFLAGS="$CXXFLAGS $switch"
- 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 switch in -std=c++$1 -std=c++0x +std=c++$1 "-h std=c++$1"; do
- cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
- AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
- $cachevar,
- [ac_save_CXXFLAGS="$CXXFLAGS"
- CXXFLAGS="$CXXFLAGS $switch"
-
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
- [eval $cachevar=yes],
- [eval $cachevar=no])
- CXXFLAGS="$ac_save_CXXFLAGS"])
- if eval test x\$$cachevar = xyes; then
- CXXFLAGS="$CXXFLAGS $switch"
- ac_success=yes
- break
- fi
- done
- fi])
- AC_LANG_POP([C++])
- if test x$ax_cxx_compile_cxx$1_required = xtrue; then
- if test x$ac_success = xno; then
- AC_MSG_ERROR([*** A compiler with support for C++$1 language features is
required.])
- fi
- else
- if test x$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)
- fi
-])
-
-
-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
-)
-
-
-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_seperators
- {
-
- 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
-
-]])
diff --git a/configure.ac b/configure.ac
index 1ba5c67..61c06a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -118,7 +118,33 @@ AC_PROG_CC
CXXFLAGS=${CXXFLAGS:=}
AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX(11, noext)
+CXX="$CXX -std=c++17"
+
+dnl Check if the compiler supports C++17: this is a rather ad hoc test as it
+dnl doesn't check for full C++17 support, but it's enough for the subset of it
+dnl that is currently used in lmi and this check passes with with g++ 6, which
+dnl can be used for compiling lmi even though it doesn't implement C++17 fully.
+m4_define([lmi_cxx_std17_test], [[
+#ifndef __cplusplus
+#error Not C++ compiler.
+#elif __cplusplus <= 201402L
+#error Only C++14.
+#else
+static_assert(true);
+#endif
+]])
+
+AC_CACHE_CHECK([whether compiler supports C++17],
+ lmi_cv_cxx_std17,
+ [
+ AC_LANG_PUSH([C++])
+ AC_COMPILE_IFELSE([AC_LANG_SOURCE([lmi_cxx_std17_test])],
+ lmi_cv_cxx_std17=yes,
+ lmi_cv_cxx_std17=no
+ )
+ AC_LANG_POP([C++])
+ ]
+)
AC_PROG_LD