[Bug c++/77562] New: large amount of memory usage when allocating big arrays

["programmerjake at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77562

            Bug ID: 77562
           Summary: large amount of memory usage when allocating big
                    arrays
           Product: gcc
           Version: 6.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: programmerjake at gmail dot com
  Target Milestone: ---

when using gcc 5+, compiling the following code uses a huge amount of memory
creating a read-only template object. On gcc 4.9 and before, it does the
expected thing, filling the array in a loop without a source object that it's
copying from.

code:
struct S
{
  long a = 1;
};

template <typename T, unsigned long N>
struct A
{
  T value[N];
};

void *fn()
{
  return new A<A<A<S, 400>, 400>, 400>;
}