[Bug c++/82760] New: Incorrect code generated for aligned new

[jarek at jpelczar dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82760

            Bug ID: 82760
           Summary: Incorrect code generated for aligned new
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jarek at jpelczar dot com
  Target Milestone: ---

Created attachment 42493
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42493&action=edit
Source code, temps,

It seems that the following type of code creates memory overwrite condition.
When I compile code with -std=c++17. Compiling code with c++11 seems to be
fine.

It turns out that the returned pointer by operator new with std::align_val_t is
fine, but GCC will move the final pointer by 0x40, so this will cause
overwriting of the next allocation.


struct aligned_foo {
        char            x[2048];

        ~aligned_foo();
        aligned_foo() { memset(x, 0, sizeof(x)); }
} __attribute__((aligned(64)));

aligned_foo * gFoo;

void test(int count)
{
        gFoo = new(std::nothrow) aligned_foo[count];
}

int main()
{
        test(2);
        return 0;
}

aligned_foo::~aligned_foo() {
}