c++ - Static array overflows stack (seg fault 11) only when inside class definition, but not otherwise...? -

i'd allocate large static array (-- want avoid dynamic allocation, e.g. std::vector, or using 'new', can guarantee physical addresses consecutive , can prefetched effectively). array size determined external factors, they're known ahead of time -- in example, i'll need 3211264 elements.

if allocate float array, works fine:

    #include <iostream>     #include <cstdlib>      using namespace std;      float f[3211264];      int main()     {       for(int = 0; < 3211264; i++)           f[i] = rand();        for(int = 0; < 3211264; i++)           cout << f[i];     } 

however, if wrap array within class, causes seg fault:

    #include <iostream>     #include <cstdlib>      using namespace std;      class t     {       public:         t();        private:         float f[3211264];     };       t::t()     {         for(int = 0; < 3211264; i++)             f[i] = rand();          for(int = 0; < 3211264; i++)             cout << f[i];      }      int main()     {         t myt;     } 

how memory being allocated, , there reason why it's different when wrap data inside class?

i'd hope class overhead minimal, , object-based re-alignment or padding at-most page side (4k), right? me, class readability , organization, if it's going have major impact on performance, i'd ditch , declare bunch of globals...

my compiler info:

configured with: --prefix=/applications/xcode.app/contents/developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1

apple llvm version 7.3.0 (clang-703.0.29)

target: x86_64-apple-darwin15.6.0

thread model: posix

in code make array class member not being statically allocated. if said:

static t myt; 

though can't believe allocating statically give serious performance increase.