gistfile1.txt

ncdev-edge-musl-x86:~/test/max_align_t$ g++ -std=c++11 a.cpp
In file included from /usr/include/stddef.h:17:0,
                 from /usr/include/c++/4.8.3/cstddef:42,
                 from a.cpp:2:
/usr/include/bits/alltypes.h:75:27: error: expected identifier before numeric constant
 typedef struct { _Alignas(8) long long __ll; long double __ld; } max_align_t;
                           ^
/usr/include/bits/alltypes.h:75:27: error: expected ',' or '...' before numeric constant
/usr/include/bits/alltypes.h:75:28: error: expected ';' at end of member declaration
 typedef struct { _Alignas(8) long long __ll; long double __ld; } max_align_t;
                            ^
ncdev-edge-musl-x86:~/test/max_align_t$ cat a.cpp 
#include <iostream>
#include <cstddef>
int main()
{
    std::cout << alignof(::max_align_t) << '\n';
}
ncdev-edge-musl-x86:~/test/max_align_t$