Trying to compile two versions (one old, one new) of some genome research software with the same version of gcc (4.4.7). The configure script checks g++ for support for C++11 features. In the old version of the software, this passes when testing g++ with -std=gnu++0x, while in the new version, none of checks (including with -std=gnu++0x) pass. Any idea what's going on?
Trimmed output of ./configure for old version of software:
checking whether g++ supports C++11 features by default... no
checking whether g++ supports C++11 features with -std=gnu++11... no
checking whether g++ supports C++11 features with -std=gnu++0x... yes
Trimmed output of ./configure for new version of software:
checking whether g++ supports C++11 features by default... no
checking whether g++ supports C++11 features with -std=gnu++11... no
checking whether g++ supports C++11 features with -std=gnu++0x... no
checking whether g++ supports C++11 features with -std=c++11... no
checking whether g++ supports C++11 features with -std=c++0x... no
checking whether g++ supports C++11 features with +std=c++11... no
checking whether g++ supports C++11 features with -h std=c++11... no
configure: error: *** A compiler with support for C++11 language features is required.
I'm not very knowledgable with C++ and what all goes on in configure scripts, but looking at where the test happens, there is a longer (more thorough?) script that gets tested in the new version.
-std=gnu++0x test in old version configure script:
for switch in -std=gnu++11 -std=gnu++0x; do
cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
$as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
if eval "test \"\${$cachevar+set}\"" = set; then :
$as_echo_n "(cached) " >&6
else
ac_save_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $switch"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
template <typename T>
struct check
{
static_assert(sizeof(int) <= sizeof(T), "not big enough");
};
typedef check<check<bool>> right_angle_brackets;
int a;
decltype(a) b;
typedef check<int> check_type;
check_type c;
check_type&& cr = static_cast<check_type&&>(c);
auto d = a;
_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
eval $cachevar=yes
else
eval $cachevar=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
CXXFLAGS="$ac_save_CXXFLAGS"
fi
eval ac_res=\$$cachevar
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
$as_echo "$ac_res" >&6; }
if eval test x\$$cachevar = xyes; then
CXXFLAGS="$CXXFLAGS $switch"
ac_success=yes
break
fi
done
-std=gnu++0x test in new version configure script:
for switch in -std=gnu++11 -std=gnu++0x; do
cachevar=`$as_echo "ax_cv_cxx_compile_cxx11_$switch" | $as_tr_sh`
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports C++11 features with $switch" >&5
$as_echo_n "checking whether $CXX supports C++11 features with $switch... " >&6; }
if eval \${$cachevar+:} false; then :
$as_echo_n "(cached) " >&6
else
ac_save_CXX="$CXX"
CXX="$CXX $switch"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
// 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
_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
eval $cachevar=yes
else
eval $cachevar=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
CXX="$ac_save_CXX"
fi
eval ac_res=\$$cachevar
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
$as_echo "$ac_res" >&6; }
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
(FYI, both versions compile fine with gcc 4.9.2 [using software collections on RHEL 6], but extremely curious as to what's going on here)
